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Blazer, Mark A.
Architectural strategies in reducing heat gain in the sub-tropical urban heat island
h [electronic resource] /
by Mark A. Blazer.
[Tampa, Fla] :
b University of South Florida,
Title from PDF of title page.
Document formatted into pages; contains 152 pages.
Thesis (M.Arch.)--University of South Florida, 2008.
Includes bibliographical references.
Text (Electronic thesis) in PDF format.
ABSTRACT: Most scientists agree that the earth's temperature continues to rise. The heat gain is more pronounced in urban areas due to a phenomenon known as the urban heat island effect. The urban heat island effect is a seemingly inevitable result of urban development, which has far reaching consequences. With energy costs skyrocketing and the destruction of the environment at risk, urban structures and buildings must do more to make our urban settings more environmentally friendly. So far, there are two well known ways to combat these effects. First, the heat island can be slightly be negated by adding well-watered vegetation to a site. Second, is to use building materials and systems that reflect the light, thus increasing the overall albedo of an urban area. Albedo is the ratio of the light energy is reflected compared that of which is absorbed. The combinations of these two practices are some of the components in green architecture. To Date, the United States has been slow to adopt policies that reduce the urban heat gain. Likewise, developers have been hesitant to construct these buildings due to implied cost and lack of knowledge. The intent of this project is to show that there are many strategies and design features that can be implemented to combat the urban heat island effect, even in the most challenging locations. The project will also employ green architecture methods in a commercial sector that has yet to fully grasp the potential to reduce heat gain and lower the urban heat island effects. To aid in the research, this project will detail buildings that are already addressing the urban heat island. The document will identify the most effective and inexpensive ways to solve this problem. It will also describe what can be done to reduce heat waste generated by lighting and cooling. In doing so, the information garnered should lead to design strategies that new buildings can utilize to reduce the urban heat island effect.
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Advisor: Daniel Powers, M.Arch.
t USF Electronic Theses and Dissertations.
Architectural Strategies in Reducing Heat Gain in the Sub-Tropical Urban Heat Island by Mark A. Blazer A thesis submitted in partial fulfillment of the requirements for the degree of Master of Architecture School of Architecture and Community Design College of Visual and Performing Arts University of South Florida Major Professor: Dan Powers, M. Arch. John McKenna, M. Arch. Daniel Yeh, Ph.D. Date of Approval: November 18, 2008 Keywords: Energy Conservation, Office Building, Faade Specialization, Roof Garden, Solar Orientation Copyright 2008, Mark A. Blazer
This thesis is dedicated to my Dad and Mom, Gary and Karen Blazer. Without their love and support who knows how things may have turned out.
a a a ACKNOWLEDGEMENTS First, I would like to start off by than king my thesis chair Daniel Powers. Without Dans insight and constant corr oboration, this project would not have been resolved and justified to the level I thought possible. I truly value his numerous critiques, his various sugges tions and examples, and especially his sense of purpose. Second, much gratitude and thanks to my thesis committee members John McKenna and Dr. Daniel Yeh. Thei r knowledge and expertise helped guide me in the right direction. No doubt t he project would have had many loose ends without their help. Third, I wanted to thank David Hunter at Beck Construction. Dave was able to get me the tools and advise which allowed me to analyze a unique perspective of my project. Fourth, I wanted to thank Jennifer Isenbeck for sitting down with me to teach me about energy savings system. That knowledge I will take with me for the rest of my career. I also wanted to thank these select individuals though-out my lifetime for helping me obtain my level of academic achievement. To Joseph Ciontea, my first architecture teacher, much thanks for his enthusiasm when I first began this
architectural journey at Goodrich High sch ool. Without his suggestions I might have regretted going into some other fiel d of study. To Rodney Hynek, I want thank him for all encouragement and pushing me to achieve to my highest ability. Finally, many thanks to Craig Salley for taking a chance on hiring me years back to my first architectural position. Work ing for Mr. Salley was one of the best jobs I ever had and without the enjoy ment of working for his firm I likely would have burned out or switched my career choice.
i space space space TABLE OF CONTENTS List of Tables iv List of Figures v Abstract xi Chapter 1 Urban Heat Island Effe ct 1 Introduction 1 Components 2 Consequences 5 Conclusion 5 Chapter 2 Building Strategies to Mitigating Urban Heat Island Effect s 7 Introduction 7 Direct Radiant Gain 7 Ambient Gain 14 Waste Heat 19 Conclusion 22 Chapter 3 Urban Forests 24 Introduction 24 Benefits 25 Distribution 29 Green Roofs 31 Conclusion 31 Chapter 4 Exterior Wall Syst ems 33 Introduction 33 Double Wall Systems 34 Energy Recovery Ventilation 37 Conclusion 39 Chapter 5 Site Selection 40 Introduction 40 Reverse Site Analysis 41 Selection Criteria 41
ii Chapter 6 Site Analysis 44 General 44 Climate 46 Surrounding Influences 50 Access 56 Zoning Regulation 57 Chapter 7 Office Buildings With Self Contained Parking 60 Introduction 60 Parking 60 Building Core and Leasable Office Space 65 Ground Level Program 68 Conclusion 70 Chapter 8 Program 71 Introduction 71 Goals and Objectives 72 Cultural Issues 73 Public transportation 75 Parking 75 Vehicle Functions 76 Time Use 77 Exterior Spaces 78 Landscaping Requirements 79 Circulation Issues 79 Separate Access Requirements 80 Sustainability Issues 81 Security Issues and Requirements 81 Solid waste Collection 82 Adaptability and Flexibility Issues 82 Day Lighting Requirement for Occ upied Spaces 83 HVAC Systems 83 Other Mechanical Systems 84 Chapter 9 Goal and Objectives 87 Chapter 10 Design Proposal 89 Introduction 90 Orientation and Site Layout 90 Faade Specialization and Indivi dualization 101 Green Roofs 110 Additional Graphics of Design Proposal 112
iii Chapter 11 Summary 117 Introduction 117 Cost Analysis 117 Energy Analysis 118 Energy Recovery Analysis 122 Conclusion 122 References 124 Bibliography 127 Appendices 131 Appendix A: Energy Analysi s One 132 Appendix B: Energy Analysi s Two 137 Appendix C: Energy Analysis Three 142 Appendix D: ERV Data 147
iv space space space LIST OF TABLES Table 2.1 Reflectivity Level of Vari ous Surfaces 8 Table 3.1 Energy Conserved and Associated Dollar Value in 2007 26 Table 3.2 Pollutants Removed by Sh rubs and Trees 27 Table 3.3 Total Value of Tampas Urban Forest 28 Table 8.1 Typical Office Floor Pr ogram 85 Table 8.2 Ground Floor Program 85
v space space space LIST OF FIGURES Figure 1.1 Urban Heat Island Profile 2 Figure 1.2 Albedo Qualities of Various Surfaces 3 Figure 1.3 Light Energy Reflection in t he Various Settings 4 Figure 2.1 Cooling Needs in the U.S. Climate Zone 5 9 Figure 2.2 Tree Sun Shading 10 Figure 2.3 Horizontal Overhang 11 Figure 2.4 Horizontal Louver 11 Figure 2.5 Vertical Louvers 12 Figure 2.6 Eggcrates 12 Figure 2.7 Eggcrates on the Sam Gibbons Couthouse by HOK 12 Figure 2.8 Temperature Difference of Refl ective Insulation 13 Figure 2.9 Vines on an Existing Building 14 Figure 2.10 Evapotranspiration Pr ocess 15 Figure 2.11 Double Wall S ystem Venting Away Ambient Heat 16 Figure 2.12 Traditional Thermal Insu lation 17 Figure 2.13 Radiant Floor S ystem Verses Typical Concre te Floor 18 Figure 2.14 Hearst Towers Radiant Floor 19 Figure 2.15 Energy Demands 20
vi Figure 2.16 Typical Light Shel f 21 Figure 2.17 Hyperbolic Light Sh elf 21 Figure 2.18 San Francisco Federal Building 22 Figure 3.1 Tampas Carbon Storage in t he Tree Canopy 28 Figure 3.2 Tampas Annual Carbon Sequester ed in the Tree Canopy 28 Figure 3.3 Hillsborough Count y Map of Tree Distributio n 30 Figure 4.1 Typical Double Wall 34 Figure 4.2 SJC Wall Section 35 Figure 4.3 SJC Model 35 Figure 4.4 SJC Louver Detail 35 Figure 4.5 New York Times Buildings Ceramic-rod Screen 36 Figure 4.6 Earth to Air HRV 37 Figure 4.7 Rotary Enthalpy Wheel 39 Figure 5.1 Koppen Climate Map of Sub-Tropical Regi ons 41 Figure 5.2 Tampas Temperature Range 42 Figure 5.3 Tampas Prec ipitation Range 42 Figure 5.4 Downtown Tampa 43 Figure 6.1 Satellite Photo of Downtown Tampa and Surroundings 45 Figure 6.2 District Map of Downtown Tampa 45 Figure 6.3 Street Boundaries of 610 N. Franklin Street 46 Figure 6.4 Tampas Possible Sunshi ne Range 47 Figure 6.5 Tampas Solar Chart 48 Figure 6.6 Typical Wind Convergence 49
vii Figure 6.7 Ground Level Usage 51 Figure 6.8 Plaza on Corner of Franklin St reet and Zack Street 52 Figure 6.9 Franklin Exchange Plaza 52 Figure 6.10 Twiggs Street Shops and Cafes 53 Figure 6.11 Franklin and Twiggs Inters ection Looking South 53 Figure 6.12 Historic Franklin Excha nge Building 54 Figure 6.13 Vacant Retail Under S kypoint 54 Figure 6.14 Lack of Development on Tampa Street Looking North 55 Figure 6.15 Lack of Development on Tampa Street Looking So uth 55 Figure 6.16 Right-of-ways of Various Travel Methods 56 Figure 7.1 Vertical Layout of 501 K ennedy Boulevard 62 Figure 7.2 Vertical Layout of the Franklin Exchange 62 Figure 7.3 Vertical Layout of Park Tower 63 Figure 7.4 Parking Entry and Exit of to Park Tower 64 Figure 7.5 Design Elements on Skypoint s Parking Garage 65 Figure 7.6 Fourteenth Floor of Park Tower 66 Figure 7.7 Typical Office Floor at 501 Kennedy 67 Figure 7.8 Porte Cochere at 501 Kennedy Boulevard 68 Figure 7.9 Franklin Exchange Ground Lev el 69 Figure 8.1 Typical Vertical Usage Layout 72 Figure 8.2 Cultural Features 74 Figure 8.3 Downtown Public Parking 76 Figure 8.4 Tampa City Center 78
viii Figure 8.5 Typical Floor Layout 86 Figure 8.6 Vertical Adjacency Dia gram 86 Figure 10.1 Office Tower Proposal 89 Figure 10.2 Site Model 91 Figure 10.3 Site Model 92 Figure 10.4 Site Model 92 Figure 10.5 Tower Orientation 93 Figure 10.6 First Floor Plan 94 Figure 10.7 Second Floor Plan 95 Figure 10.8 Third Floor Plan 96 Figure 10.9 Fifth Floor Plan 97 Figure 10.10 Ninth Floor Plan 98 Figure 10.11 Twelfth and Twenty Second Floor Plan 99 Figure 10.12 Twenty Fifth and Twenty Nin th Floor Plan 100 Figure 10.13 Light Study 102 Figure 10.14 Light Study 102 Figure 10.15 Light Study 102 Figure 10.16 Light Study 102 Figure 10.17 Light Study 102 Figure 10.18 Light Study 102 Figure 10.19 South Elevation 103 Figure 10.20 West Elevation 103 Figure 10.21 South Faade Tower Section 104
ix Figure 10.22 North Faade Tower Section 105 Figure 10.23 Double Wall System 106 Figure 10.24 Double Wall System V ent Stack 107 Figure 10.25 Building Section Showi ng Overall Shading 108 Figure 10.26 Retail Level Section Model 109 Figure 10.27 Entry Plaza 110 Figure 10.28 Roof-top Garden Locat ions 111 Figure 10.29 Site Rendering 112 Figure 10.30 Tower Perspective 112 Figure 10.31 Model Showing East Facade 113 Figure 10.32 Model Showing South Facade 114 Figure 10.33 Model Showing West Facade 115 Figure 10.34 Model Showing North Facade 116 Figure 11.1 Model Showing North Facade 120 Figure 11.2 Model Showing North Facade 121 Figure 11.3 Model Showing North Facade 121 Figure A.1 Project Proposal Cost Analysis 132 Figure A.2 Project Proposal Cost Analysis 133 Figure A.3 Project Proposal Ener gy Analysis 134 Figure A.4 Project Proposal Ener gy Analysis 135 Figure A.5 Project Proposal Ener gy Analysis 136 Figure B.1 Project Proposal Cost Analysis 137 Figure B.2 Project Proposal Cost Analysis 138
x Figure B.3 Project Proposal Ener gy Analysis 139 Figure B.4 Project Proposal Ener gy Analysis 140 Figure B.5 Project Proposal Ener gy Analysis 141 Figure C.1 Project Proposal Cost Analysis 142 Figure C.2 Project Proposal Cost Analysis 143 Figure C.3 Project Proposal Ener gy Analysis 144 Figure C.4 Project Proposal Ener gy Analysis 145 Figure C.5 Project Proposal Ener gy Analysis 146 Figure D.1 Energy Recovery Wheel Data 147 Figure D.2 Energy Recovery Wheel Data 148 Figure D.3 Energy Recovery Wheel Data 149 Figure D.4 Energy Recovery Wheel Data 150 Figure D.5 Energy Recovery Wheel Data 151 Figure D.6 Energy Recovery Wheel Data 152
xi space space space ARCHITECTURAL STRATEGIES IN REDU CING HEAT GAIN IN THE SUBTROPICAL URBAN HEAT ISLAND Mark A. Blazer ABSTRACT Most scientists agree that the earths temperature continues to rise. The heat gain is more pronounced in ur ban areas due to a phenomenon known as the urban heat island effect. The urban heat island effect is a seemingly inevitable result of urban developmen t, which has far reaching consequences. With energy costs skyrocketing and the destr uction of the envir onment at risk, urban structures and buildings must do mo re to make our ur ban settings more environmentally friendly. So far, there are two well known ways to combat these effects. First, the heat island can be slightly be negated by adding well-watered vegetation to a site. Second, is to use building materi als and systems that reflect the light, thus increasing the over all albedo of an urban area. Albedo is the ratio of the light energy is reflected compared that of which is absorbed. The combinations of these two practices are some of the components in green architecture.
xii To Date, the United States has been slow to adopt policies that reduce the urban heat gain. Likewise, developers have been hesitant to construct these buildings due to implied cost and lack of kno wledge. The intent of this project is to show that there are many strat egies and design features that can be implemented to combat the urban heat island effect, even in the most challenging locations. The project will also employ green architecture methods in a commercial sector that has yet to fully grasp the potential to reduce heat gain and lower the urban heat island effects. To aid in the research, this projec t will detail buildings that are already addressing the urban heat island. The doc ument will identify t he most effective and inexpensive ways to solve this probl em. It will also describe what can be done to reduce heat waste generated by light ing and cooling. In doing so, the information garnered should lead to design strategies that new buildings can utilize to reduce the urban heat island effect.
1 CHAPTER 1 URBAN HEAT ISLAND EFFECT Introduction An urban heat island is a built-up area which is significantly warmer than its surroundings. In such an area, typically the temperature difference is usually greater at night than duri ng the day and is greater in the winter than in the summer. The main cause of an urban heat island is the modification of the lands surface by development. Waste heat, generated by energy usage, is a common secondary contributor. Growing urban center s tend to modify greater areas of land and have a corresponding increase in average temperatures (see Figure 1.1). In addition, these same urban areas will see monthly rainfall increase twenty to forty miles downw ind when compared to upwind. The rainfall is the result of hot currents rising, which then move downwind to clash with the cooler suburban air. Rain clouds will t hen tend to form with more frequency.1 By knowing how a heat island is caused, st rategies may be implemented to help mitigate or reduce its negative e ffects. Failing to confront this problem may result in irreversible damage to the surroundi ng environment and have a negative effect on the economy.
2 Figure 1.1 urban heat island profile (EPA) Components There are many causes that cont ribute to an urban heat island. One example is the presence of more dark surfaces when compared to the rural surrounding landscape. Dark roofs are very common in urban centers. Dark roofs contribute to the heat island by abs orbing a high percentage of light energy striking the roofs surface, rather than re flecting light energy away. The ability to reflect heat, termed albedo, is low among dar k surfaces (see Figure 1.2). The petroleum based roof for instance, while great for water proofing, is poor at reflecting light energy away. Another poor re flector is street pavement, especially asphalt. Not only does asphalt pavement absorb more light energy, it stores it for long periods of time. Pavement is one of the leading causes for the night time urban heat island.
3 Figure. 1.2 albedo qualities of various surfaces (EPA) Another leading cause for the heat Isl and effect is the absence or total loss of sufficiently watered vegetation. The loss of vegetation in the urban setting is often an unavoidable circumstanc e. Sparse vegetation can eliminate two important cooling mechanisms, s hade and evapotranspiration. Shade cools the air by blocking solar radiation from hitting low albedo surfaces. The reduced thermal energy prevents the surface and ambient temperatures from becoming unnaturally inflated. Evapotranspiration, on the other hand, is the result of both evaporation and plant transpiration. According to the Heat Island Group a single mature, properly watered tree with a crown of thirty feet can evapotranspire up to forty gallons of water in a day, which is like removing all the heat produced in four hours by a small electric space heater.2
4 Other causes for urban heat isla nd include the canyon effect and building/vehicular energy consumption. The canyon effect is a geometric problem commonly associated with citi es that have a concentration of skyscrapers. When light energy enters an urban core it bounces off either a building roof or building facade. In urban cores this light energy is more likely to bounce off several surfaces when com pared to rural and smaller scale urban areas (see Figure 1.3). Making matters wors e is the notion that building facades in downtown areas usually have large s pans of surface area made of glass and other reflective surfaces. Theref ore, light energy is bounced around and reflected many times, giving the energy more time to be absor bed into the urban fabric. Buildings and vehicles also add to the heat island by generating waste heat produced by their mechanical functions. Urban areas are more adversely affected by waste heat gain when compar ed to their rural counterparts because of the presence of more mechanical processes and because of the canyon effect. Figure 1.3 light energy reflection in the various settings (University of Arizona)
5 Consequences Urban heat islands have numerous impac ts on the cities in which they occur. They affect the citys clim ate, inhabitants, su rrounding ecosystems and economy. The most noticeable of thes e affects is the daily increase in temperature. According to the EPA, so me city temperatures are increased as much as 10F when compared to a nearby rural area. In conjunction with the increase in temperature, the rate of ozone formation rises. Elevated concentrations of low altitude ozone has a si gnificant effect on a citys air quality. The ozone increase is the main contributor to city smog. The increased amount of ozone can also result in a variety of human health concerns.3 The ozone also affects the health of vegetat ion and can tarnish its visual appearance. The air quality is further effected by the releas e of additional emissions and greenhouse gases through an increase use of ai r conditioning and other mechanical systems.4 Finally, there is an effect to t he economy through the increase use of energy. Air conditioning is a sizable expense for the operation budget of a business. Since the buildings within in the urban heat island need more cooling, their energy consumption and operati onal expenses will be increased. Conclusion The urban heat island is having majo r impacts on American cities. As cities grow, they pave new roads, cut down trees, and consume additional
6 energy resources. All of these factors lead to an increase in the urban heat island effects. These effects are dam aging the cities ecosystem, affecting the heath of the inhabitants and impacting the economy. Al though, causes of the heat island seem unavoidable, some bas ic strategies can be adopted to help cope with these effects. Future constr uction within the heat island area should be designed in a way to help mitigate the im pacts. With a shi ft in building design strategies, a reduction the heat island can be realized.
7 CHAPER 2 BUILDING STRATEGIES TO MITIGATE URBAN HEAT ISLAND EFFECTS Introduction Mitigating the effects of the heat island is a co mplex proposition for the design of new buildings. Not only will these buildings have to deal with the effects created by the present heat island, but the building should also be able to alleviate the future heat island effect s as well. Currently, there are many techniques that can be integrated into a buildings design to reduce a buildings core temperature, as well avoid contri buting to the current heat island effect. These techniques can be broken into thr ee categories: direct radiant gain, ambient gain and waste heat. Knowing t hese techniques, and the strategies in implementing them, will help to establish future design systems and construction methods. Direct Radiant Gain Direct radiant gain reduction techniques deal with strategies that reduce the absorption of light energy into a buildi ng. As previously indicated, a main
8 contributor to heat island is to la rge expanses of surfaces with low albedo/reflective materials. Reducing and replacing these materials with more reflective surfaces is an important heat island deterrent. A building with a light covered roof will reflect more light energy than a dark covered roof. According to Berkeleys Laboratory's Environmental Energy Technologies Division applying white paint can vastly enhance a surfaces refl ectivity. The textur e of the exterior materials is also important. A coat of white paint over a smooth surface will reflect light away better than the same paint on a rough surface (see Table 2.1). Table 2.1 reflectivity levels of various surfaces (Drexel) Reflective exterior mate rials reduce heat absorption as well. Metal roofs are a primary example. These metal r oofs are usually dur able and will reduce energy consumption. The consumption of energy is lower due the reduction of cooling needs. In the sout heast portion of the United Stat es, cooling accounts for over one tenth of all energy consumed in the average office building (see Figure 2.1).5 One problem with metal roofs is that while they prevent the conduction of heat into the building, they trap the heat energy inside the bu ilding, allowing for ambient gain. This trapping of t he heat energy makes these methods less effective than other types of roofing system s. A better metal-based roof is one
9 that is combined with a polymeric coating, so it becomes even more efficient and realizes greater energy r eduction within the building. Figure 2.1 cooling needs in U.S. climate zone five (MLGW) Other than roofs, sun exposure on t he facades also adds to a buildings heat gain. One way to reduce direct radi ant gain on exterior walls is found in the form of shading techniques. A common rural method is to use trees and shrubs to block out the suns energy from hitting the facades of the building (see Figure 2.2). Surfaces under shade are cooler than those under direct sunlight. Unfortunately because of building heights, using tree shade in urban locations is less effective than their rural counterparts. The reduction of sunlight hitting the faades is perhaps the most crucial component in decreasing heat gain for tall bu ildings. Tall buildings have a higher percentage of exposed surface area on the facade than on the roof. These buildings are also subject to light energy hitting their exteriors indirectly by the
10 Figure. 2.2 tree sun shading (author sketch) light energy reflections off of adjacent buildings. Unfortunately, tall buildings struggle to take advantage of trees. This is because most trees will not reach above their fourth story. Therefore, alternative shading techniques must be implored to reduce the heat gain on the buildings. Attached sun shading devices are one common method to shade tall buildings. Horizontal overhangs and louv ers are most effective on southern orientations (see Figure 2.3 and 2.4). The louver also allows for air circulation near the exterior wall. Air circulati on further adds to the effectiveness by reducing ambient heat gain. These louvers can be operational or can remain in a fixed position. Vertical louvers are most effective on eastern and western exposures (see Figure 2.5). These louver s may be fixed, operated manually or controlled automatically wit h photoelectric controls to adapt to the changing sun angle. Eggcrates combine elements from ho rizontal and vertical louvers (see
11 Figure 2.3 horizontal overhang (author sketch) Figure 2.4 horizontal louver (author sketch) Figure 2.6 and 2.7). Eggcrates, also referre d as brise-soleil, are very efficient for hot climates because of their high shading ratio. One disadvantage of attached sun shading techniques is that it will add to the buildings surface area. The extra surface area allows the possibility for mo re light energy to be absorbed. Then this light energy can then be conduc ted into the building without proper insulation. Additional concerns for attached sun shading must be addressed to avoid the energy conduction. These conc erns include the connections to the building, the types of material used in the construction and the color of these materials. A buildings orientation and form are other common methods used to minimize its heat gain. Firs t, for orientation, the build ing should limit the amount of exposed surfaces during peak solar gai n periods. Consulting a regions sun chart can help determine the most ef fective orientation and sun shading strategies. For example, a building with glass atriums should avoid placement where a sun chart reveals prolonged sun exposure. In building areas where
12 Upper Left, Figure 2.5 vertical louvers (author sketch) Lower Left, Figure 2.6 eggcrates (author sketch) Right, Figure 2.7 eggcrates on the Sam Gibbo ns Courthouse by HOK (author photo) intense solar gain cant be avoided, a double skin can be erected to keep much of the radiant energy off the inner wall. Second, a buildings shape can also have an effect on the buildings heat gain. A square form for instance, is not the optimal shape for a sub-tropi cal climate. The most efficient building shape in such a climate is a form that is elongated along an east-west axis.6 Buildings elongated at an east-west axis limit sun exposure on the east/west facades. The least efficient form is a building form t hat is elongated on the north south axis.
13 Reflective insulation is another way to reduce radiant heat gain. Reflective insulation resists all three ty pes of heat transfer. They are conduction, convection, and most importantly, radiant heat transfer (see Figure 2.8). The insulation incorporates both insulating and reflective materials. When properly installed, reflective insulation will re sist convective currents and provides an excellent barrier against air in filtration from the exterior.7 The insulation also is an excellent vapor retarder. A unique aspect of reflective insulation, unlike types of traditional thermal insulators, is that it does not absorb moisture. In fact, installed in conjunction with thermal insulations, it can help thermal insulation to stay dryer. Figure 2.8 temperature difference of reflec tive insulation and thermal insulation (ESP)
14 Ambient Gain Reducing ambient heat gain in the ur ban heat island involves different strategies and techniques. Ambient heat gain is most adverse in urban areas because this where the temperature is mo st inflated. Ambient temperature is non-directional and cannot be blocked out using sun shading strategies. The main premise in reducing ambient heat gain is preventing or slowing the conduction of heat from t he outside to the inside. One method of reducing ambient heat gain has been around for hundreds of years. Vines on a building can cool the adjacent exterior through evapotranspiration (see Figure 2.9). Veget ative roofs use the same process to cool the building. Trees and other vegetation cool the air is by absorbing water through their roots and evaporating it thr ough leaf pores (see Fi gure 2.10). This Figure 2.9 vines on an existing building (flicker.com)
15 Figure 2.10 evapotranspiration process (EPA) process uses heat from the air to conver t water contained in the vegetation into water vapor. Evapotranspiration alone can result in peak summer temperature reductions of 2F to 9F. While this pr ocess reduces air temperatures, it does add some moisture to the air. The positiv e cooling effect of vegetation usually outweighs any undesirable gains in humidity and can be minimized by utilizing the wind to ventilate the building. A double wall system is another way to cool the exterior faade. A double wall system uses two processes to remove the elevated ambient temperatures. First, the outer wall blocks dire ct light energy from hitting the inside wall surface. Stopping the direct light energy slows the process of heat transmitting through the inner wall. However, light energy will still hit the outer wall surface and will radiate heat off its surface. The radiatio n of heat from these surfaces will raise
16 the ambient temperature. Second, is the process of removing the heat energy for the double wall system. By creating a cavity between the two walls in the double wall system, an air movement proce ss will be formed that works similarly to a chimney. In this process, higher ai r pressure outside the cavity is drawn in. The pressure forces the air within the ca vity up and away from the building (see Figure 2.11). Figure 2.11 double wall system venting away ambient heat (author diagram) Thermal insulation is a traditional method that can reduce the ambient gain on a building. Besides providing the rmal comfort for the building occupants, thermal insulation reduces unwanted heat loss or gain and can decrease the energy demands of heating and cooling system. Some in sulation materials that can slow the transmission of heat inclu de: cellulose, fiberglass, rock wool,
17 polystyrene, urethane foam and ve rmiculite (see Figure 2.12).8 Other techniques can be implored to further address the modes of heat transfer, conduction, radiation and convection. The effectiveness of insulation is commonly evaluated by its R-value. Howe ver, an R-value does not take into account the local environmental factors or the quality of construction for each building. Construction quality issues in clude deficient vapor barriers, and problems stemming from draft-proofing. Figure 2.12 traditional insulation (Hertalan) A radiant floor system is a unique wa y to reduce ambient gain. Energy waves from the sun do not heat up the ai r, rather energy waves contact solid surfaces and then radiate the energy into the air as the surface heats up. A
18 radiant floor counteracts this process by circulating cold water through to keep the floor surface cool (see Figure 2.13). The water circulation prevents the ambient temperature from ri sing because all excess heat e nergy is circulated out. An example of this process is found in t he Hearst Tower in New York (see Figure 2.14). The Hearst Tower has a 1.7 millio n cubic foot atrium. Normally, this atrium would have required massive am ounts of energy to cool the space.9 However, the atriums radiant floor system provides a much more efficient way to keep the space cool. In addition to lo wering the ambient temperatures, the inclusion of the radiant floor system in Hearst Tower reduces waste heat that would have been generated by alternative systems. Figure 2.13 radiant floor system verses typical concrete floor (author sketch)
19 Figure 2.14 Hearst Towers radiant floor third floor (author sketch) Waste Heat Reducing waste heat deals with those strategies that limit the use of mechanical systems that generate heat as a byproduct. The simplest ways to reduce waste heat in hot c limates are to lim it the need for mechanical lighting and cooling. Lighting and cooling repres ent over fifty perc ent of the energy demands in a typical office building in the southeastern United States (see Figure 2.15).10 The integration of daylighting tec hniques can help reduce this energy demand. One such daylighti ng technique is using an architectural element know
20 Figure 2.15 energy demands (author chart derived from MLGW data) as a light shelf. A light shelf allows daylight to penetrate deep into a buildings interior. These shelves are usually hor izontal elements that overhang an exterior window. They are placed just above eye level and have a highly reflective upper surface. This surface reflects daylight ont o an interior ceiling. The light is then diffused off the ceiling and reduces the need for electrical lighting (see Figure 2.16 and 2.17). Light shelves are comm only made of an extruded aluminum or an aluminum composite panel. The extruded surfaces are usually painted or anodized. High-rise office buildings often use light shelves. Typically the light shelves are found on a buildings southern side where the maximum sunlight is found. In addition to providing interior lighting, light shelves also shade the windows below eye level to help reduce glar e. As stated, plac ement of the light shelf is generally on the exterior since that location is more effective than an interior shelve. However, a combination of exterior and interior shelves can work even better in providing daylightin g far into the building.
21 Figure 2.16 typical light shelf (www.schorsch.com) Figure 2.17 hyperbolic light shelf (www.schorsch.com) One recent project, The San Franc isco Federal Building, takes the reduction of waste heat to a whole new level (see Figure 2.18). The Federal Building was designed to consume less t han half the energy of a typical office tower. One way the building has reduced energy consumption is the implementation of natural ventilation. In doing so, the Federal Building became the first building on the west coast to us e no air conditioning in over fifty years.11 In addition, The building further reduces energy consumption by featuring elevators that stop only on every third fl oor. Building occupants exit elevators
22 and then either walk up or down one fli ght of stairs. There is, however, one elevator which stops on every fl oor for those unable or unwilling to navigate stairs. Unfortunately, the Federal Building has been criticized as being dysfunctional for its employees.12 According to an employee interviewed by BeyondChron.com "Workers seek to relieve the heat by opening windows, which not only sends papers flying, but, depending on their proximity to the opening, makes creating a stable temperature for all workers near impossible... some employees must use umbrellas to k eep the sun out of their cubicles.13 Figure 2.18 San Francisco Federal Building (San Francisco Chronicle) Conclusion There are many design strategies a new building can adopt to reduce its susceptibility and contribution to the urban heat island. Depending on the climate, some strategies out lined may be more or less effect ive. It is important to identify the unique characterist ics of a site to determine what strategies will work
23 the best. When this is done and is co mbined with a thorough design process, reduction of the urban heat island may be possible.
24 CHAPTER 3 URBAN FORESTS Introduction An urban forest is a collection of trees, shrubs and grasses that grow within a city, town or suburb. The urban fo rest can comprise of just a few trees and other smaller vegetation like that withi n a roof garden or can be comprised of several square miles like that of Central Park in New York. Regardless of the size, an urban forest plays a key role in the ecology of human habitats. The urban forest filters the ai r, water and sunlight, and provides relief to the inhabitants during hot or in clement weather. The urban forest moderates local climates by slowing wind and stormwater and shades buildings, which in turn can provide an energy savings. Such forest s are also critical in mitigating the urban heat island effect and can lower t he level of unhealthy ozone that plague cities during the summer months.14 This chapter analyzes the recent study of Tampas urban forest and hi ghlights the reasons why such a forest is an important part of the citys landscape.
25 Benefits There are many benefits in having an urban forest. Perhaps the most appealing of these is urban beautification. The presence of trees has been shown to reduce stress and has long been seen to benefit to the health of urban dwellers. The shaded areas provided by the urban forest and other green spaces, create places for people to socialize and play. Trees also provide nesting sites and food for birds and other animals. People appreciate watching, feeding, photographing, painting ur ban trees, and wildlife. Urban trees and wildlife help people maintain their connection with nature. Another benefit to the ur ban forest is energy conservation. Trees near a building can provide shade dur ing the day, which in turn reduces energy needs to cool the building during the summer. Depending on th e species of tree and the latitude of the location, energy consumpt ion can be raised or lowered during the winter months. In addition to blocking out light energy, a forest canopy can also act as a windbreak. The windbreak can further reduce heat loss during the winter. In the City of Tampa Urban Ecological Analysis (CTUEA), an experiment was done to find out the amount of energy conserved by tree shade. The trees in the experiment were twenty feet ta ll and were less than si xty feet from the observed building15. The CTUEA found that Tampa s current tree canopy saves nearly 35,000 megawatt hours of electric ity per year (see Table 3.1). In monetary terms, the reduction in energy co nsumption was worth just under four million dollars.
26 Table 3.1 energy conserved and associated dollar value in 2007 ( CTUEA ) Removal of air pollution is another valuable asset of the urban canopy. Excess air pollutants can create smog and le ad to adverse health issues. Some of these pollutants include: carbon monoxide, nitrogen dioxide, ground level ozone, sulfur dioxide and particle matter. Nitrogen dioxide is also a respiratory irritant and can cause a series of heal th problems. Nitrogen dioxide is an ingredient for the formation of low level oz one as well. As stated in Chapter 1, ozone can cause a variety of health issues as well lead to smog. Trees within a city can cleanse the air of these and other pollutants. A com puter model for the CTUEA estimated that Tampas tree and shrub population removed 1,360 tons of air pollution in 2007.16 Further analysis suggests that if artificial ways would have been used to cleanse the same tonnage of po llutants, the cost would have been well over six million do llars (see Table 3.2).
27 Table 3.2 pollutants removed by shrubs and trees ( CTUEA ) Finally, a tree canopy can store and s equester carbon. Carbon dioxide, a greenhouse gas, is used by trees in the process of photosynthesis. As trees grow they incorporate atmospheric carbon into their tissue and st ore it for life. The removal of carbon from the atmos phere is important because excess carbon dioxide can have a global effect on the earths temperature. The CTUEA did a study on the carbon removed from the at mosphere by Tampas trees (see Figure 3.1 and 3.2). The study also determi ned the amount of ca rbon that Tampas urban forest holds, the amount of ca rbon it sequesters each year, and the monetary value of removing the same amount of carbon using artificial methods (see Table 3.3).
28 Figure 3.1 Tampas carbon storage in the tree canopy (CTUEA) Figure 3.2 Tampas annual carbon sequestered in the tree canopy (CTUEA) Table 3.3 total value of Tampas urban forest ( CTUEA )
29 Distribution For the urban forest, it is important that the canopy be evenly spread out. An even distribution will lessen the chance stagnant pockets forming. Unfortunately, some locations within ci ties are lacking in tree and shrub canopy coverage. For instance, the tree coverage in a typi cal downtown location is lacking because economic factors have forced the roads and buildings closer together. The result is that downtown buildings will occupy a higher percentage of the land over the less dense rural areas. The CTUEA shows that Tampa follows this pattern (see Figure 3.3) The small canopy coverage makes downtown Tampa very susceptible to air pollution generation and stagnation. City wide, Tampas canopy coverage is twenty-nine percent. Downtown was found to be at only five percent.17 Other areas with similarly low canopy coverage were the airports in West Tampa and South Tampa along with various industrial zones. On the other end of t he spectrum, areas along the river and bay usually had higher canopy coverage. Although the CTUEA does not indicate an optimal level of canopy coverage, maximization of the tree canopy coverage has quantifiable benefits where as leaving areas barren or underutilized is unsatisfactory.
30 Figure 3.3 Hillsborough county map of tree canopy coverage (CTUEA)
31 Roof garden One important building applic ation of the urban forest is the green roof. A green roof is a building roof that is partially or completely covered by vegetation and soil over a waterproof membrane. In general, green roofs consist of grasses and other small shrubs but may also have tr ees as. In addition to providing an aesthetic ambiance, green r oofs have also been found to dramatically improve a roofs insulation value. As stated in c hapter two, an additional important quality of the green roof is the lowering of the am bient temperature through the process of evapotranspiration. A third positive aspec t of the green roof is the ability to reduce stormwater run-off. Unfortunately, use of the green roof has found slow adoption within the United States due to added cost s of maintenance and structural requirements. However, when planned properly in the design phase, the added costs can often be offset by a building that will have a reduced energy demand. Conclusion The value of the urban forest is mo re than just in beauty, it protects peoples health, conserves energy and sa ves money. Unfortunately, this protection is limited for the city because of overdevelopment and underutilization. This has caused many city areas to have either low canopy coverage or none at all. It is important that, regardle ss how developed an area becomes, the location
32 should always perverse trees and shrubs w here possible. In addition, designers and planners should consider the adapt ation of green roofs early in the schematic phase as an additional means to attain the benefits of the urban forest.
33 CHAPTER 4 ENERGY SAVING SYSTEMS Introduction The energy saving systems in a building play an important role in the heat island effect by limiting waste heat pr oduction. Waste heat reduction will lower the ambient heat of an area because less heat is generated through artificial means. Energy saving systems can take on many forms. Some are moderately small devices located in a mechanical r oom, like an air-to-air enthalpy wheel. While others can be a large architectural feature of a building like a double wall system. Regardless of their size and features, energy saving systems will ultimately reduce the energy consumpti on of a building, thus reducing waste heat. Double Wall Systems Double walls, or cavity walls, hav e been created for two main purposes. One is to provide the building nat ural lighting control with maximum transparency, while the other is to reduce the heating or cooling load by lowering the U-value beyond what a single wall coul d do alone. In essence, they create
34 an additional thermal buffer. Depending on the climate, the features and purposes of a double wall systems differ. Fo r instance, in cool and cold climates, the double wall cavity is often not vent ed and heat is trapped and transmitted to the interior. Conversely, double walls in hot climates will require the air cavity to be vented and the moisture level controll ed. The vents in this system are typically located in the spandrel between the floor and ceiling below (see Figure 4.1). The use of a double wall system has long been popular in Europe, but has found limited use within the United States due to less strict efficiency codes Figure 4.1 typical double wall (Katz) The United States does, however, have a few existing projects utilizing the double wall. One such project is the Seattl e Justice Center (SJC). This building has a large section of the west faade using a double skin that is naturally ventilated. The double skin is composed of two separate planes of glass spaced
35 30 inches apart. This system allows for t he penetration of light into the interior space but limits interior heat gain. T he reduction of heat gain allows the building to reduce its heating and cooling needs, in turn reducing waste heat. Interior light shelves are used in conjunction wit h the double wall system in an effort to both reduce the direct heat gain and filter in natural light. In addition, the double wall system at the Seattle Justice Center utilizes automatically controlled louvers at the roof level to release or retain the heat. During the winter months these louvers are closed, and during the summe r they are open (see Figure 4.2 4.4). Figure 4.2 SJC wall section, Figure 4.3 model of SJC, Figure 4.4 SJC louver detail (NBBJ)
36 Another project within t he United States to use a double wall system is the New York Times Building. The uniqu e feature on the Times faade is the ceramic-rod screen system (see Figure 4.5) The ceramic-rod screen is placed one and a half feet in front of the interior glass curtai n wall. These rods block direct radiant gain but also serve as a convex light shelf. Perhaps the most intriguing fact of the rods, is that they are spectrum se lective. The rods will only reflect in the cool color spectrum, t hus reducing cooling needs even further. Other features of t he Times Building include the use of fully glazed low-e glass, mechanical shades controlled by sensors to reduce glare, and more than 18,000 individually-dimmable fluorescent fixt ures to supplement natural light.18 On top of the environmental gains the ceramic-r od screen provides, the screen changes color throughout the day and is dependent on the weather. This offers an appealing aesthetic quality. Figure 4.5 New York Times Buildings ceramic-rod screen (Science-Beat)
37 Energy Recovery Systems An energy recovery system is a me chanical system t hat exchanges the embodied energy contained withi n a regular building exhaust with the incoming outdoor air. The main benefit of these systems is the abil ity of a building to meet construction efficiency standards, improv e indoor air quality and reduce the total HVAC capacity. There are two main types of energy recovery systems. First is the Heat Recovery Ventilator (HRV). HRVs are limited to only transferring sensible heat. Sensible heat is defined as potential energy in the form of thermal energy or heat. Beside just transferring heat to save on energy needs, HRVs provide fresh air and improve climate cont rol. Common types of HRVs include heat pipes, rotary heat exchanger and a cross-flow heat exchanger. A unique, but less common example is an earth to ai r HRV (see Figure 4.6). Earth to air heat exchangers use air cool ed underground air rather t han regular outside air. Figure 4.6 earth to air HRV
38 One advantage of this method is the fact that the air underground remains at a fairly constant temperature. The second type of energy recovery system is energy recovery ventilators (ERV). ERVs get their inherent value by being able to transfer both sensible heat and latent heat. The trans fer of latent heat entails the ability to transfer energy during a phase transition. For exam ple, the transfer of energy as water transforms from a gas to a liquid. Two types of ERVs include fixed plates and rotary enthalpy wheels. The rotary ent halpy wheel is a circular heat exchanger which operates on the air-to-air process of heat transfer (see Figure 4.7). It provides an excellent way of recove ring energy embodied in conditioned air for hot, humid climates. The process begins with cool and dry exhaust air entering one side of the revolving enthalpy wheel. This chills and dries the wheels desiccant coating. The cool and dry part of the wheel then turn into the supply air where it absorbs heat and humidity from the incomi ng fresh air before Figure 4.7 rotary enthalpy wheel (Xetex)
39 the air is mechanically cooled to room te mperature. The rotary enthalpy wheel can reduce the air-conditioning load by nearly ninety percent.19 The lower load capacity will save energy and reduce the size of the required HVAC equipment. Conclusion Knowing the types and complexities of varied energy saving systems is crucial for contemporary building design. Significant growth in this field has occurred in the past decade and future brea kthroughs are surely on the way. It important to constantly review new tec hniques and strategies to find out what direction would be most appropriate consider ing a buildings location and climate.
40 CHAPTER 5 SITE SELECTON Introduction Reducing a buildings heat gain require s a unique set of strategies when addressing the heat island effect in subtropical urban areas. Currently, there are many strategies when dealin g with the heat island effect. However, there are few examples that apply these current stra tegies to the urban cores within subtropical regions. Many of the traditional st rategies that combat the heat island effect do not work well, or at all, in s ub-tropical urban cores. A proper site within the sub-tropical urban core must be identified so a strategy may then be developed to best address the heat gain problem. Reverse Site Analysis There are many elements involved in choosing a suitable site for this project. The site needs to be in a sub-tropical area and within a dense urban core of a large city. T he sites location should be unable to take advantage of methods used in rural sites and should also have additional adverse conditions that make its location even more gravel y affected by the heat island effect.
S T r e t h p w s K r o t e w l e t e a t h F i S election C r T aking the p e quiremen t h e corner o resently is w ith the he a ub-tropical K oppen Cli m o ughly bet w e mperatur e w armest m o e ast 1.5 in c e nth of the reas like A t h ese chara c i gure 5.1 Kop p r iteria p ervious fa c t s would b e o f Franklin S ready to b e a t island eff e climates e n m ate Class i w een latitu d e of the cli m o nth is to b e c hes per m o precipitati o t lanta, G A ; c teristics ( s p en climate m a c tors into a c e in downto w S treet and Z e redevelo p e ct in subt n tail warm, i fication su d es 40 an d m ate is bet w e above 72 o nth, while o n during th Houston, T s ee Figure 5 a p of sub-tropi c 41 c count, on e w n Tampa. Z ack Stree t p ed. A s st a t ropical urb a humid an d b-tropical a d 25 North w een 30F a F. For pr e the winter m e wettest m T X; Charlot t 5 .2 and 5. 3 c al regions (Wi e such site More spe t in the do w a ted, the su a n areas. T d wet condi t a reas in th e and Sout h a nd 64F i n e cipitation, t m onths will m onths.21 M t e, NC; an d 3 ). The se c kimedia Com m comprisin g cifically, a v w ntown are a bject of thi s T he gener a t ions.20 A c e northern h h (see Figu r n the winter t he summ e get appro x M ajor U.S. m d Tampa, F c ond impor t m ons) g of all of th v acant lot o a which s project d e a l distinctio n cording to t h emispher e r e 5.1). Th e and the e r months g x imately o n m etropolita F L all share t ant ese o n e als n s of t he e lie e g et at n e n
42 Figure 5.2 Tampas temperature range (rssWeather.com) Figure 5.3 Tampas precipit ation range (rssWeather.com)
43 requirement is a site within of a dense ur ban core. The city of Tampa meets this requirement. According the U.S. Census Bureau, the Tampa, St. Petersburg and Clearwater metropolitan area ranks as the nineteenth largest me tro in the U.S., with 2.7 million people in 2007.22 In addition, the city of Tampa has a dense urban core. Tampas Central Business Distr ict is centered over the intersection of Franklin Street and Kennedy Boulevard. The corner of Franklin Street and Zack Street for this project also has a many disadvantages over other sites. The site is small and expensive. These characteristics will require any future constr uction to be high density in nature. In addition, the site is flat and surrounded on all four sides by asphalt paved streets (see Figure 5.4). Finally, because of the ta ll buildings, this site will suffer from the canyon effect. The canyon effect leads to an increase in temperature due to light energy bouncing off many building fa cades, allowing the light energy more time to be absorbed by the surrounding environment. The combination of all these factors is why 610 N. Franklin St reet is an acceptable selection. Figure 5.4 downtown Tampa (image modified from Google Earth)
44 a a a CHAPTER 6 SITE ANALYSIS General As stated, the building site is lo cated in downtown Tampa. The surrounding neighborhoods include the Univ ersity of Tampa and Hyde Park to the west and southwest. Located to the nor th is Tampa Heights and to the east is Ybor City. The Channelside District is situated to the southeast and to the south are Davis and Habour Islands (see Fi gure 6.1). Focusing in towards the site location, the downtown area is brok en into many districts. The site is currently located in downtown Tampas Frank lin Street District (see Figure 6.2). The Franklin Street District includes a ma jor retail corridor and has the highest concentration of office towers in the area. Focusing further, the site is bounded by four streets; Zack Str eet to the north, Franklin Street to the east, Twiggs Street to the south, and Ta mpa Street to the west (s ee Figure 6.3). Both Tampa Street and Zack Street are one-way streets, while Twig gs Street and Franklin Street are two way st reets. Similar to other dow ntown blocks, the dimensions are 210 feet by 210 feet.
45 Figure 6.1 satellite photo of downtown Tampa and surrounding neighborhoods (Google Earth) Figure 6.2 district map of downtow n Tampa (image modified from Municode)
46 Figure 6.3 street boundaries and showing in blue the location of 610 N. Franklin Street. (image modified from Google Earth) Climate Knowledge of a sites climate is a cr itical element to take into account when developing a project. The city of Tampa is no exception and has a variety of important factors to c onsider. Tampas average high temperature ranges from 52F in January to 90F in July (see Figure 5.2). Tampas precipitation is stable throughout the spring, fall and winter months, averaging from one and half inches to three inches per month (see Figure 5. 3). The summer contains by far, the wettest months. Summer rainfall peri ods are normally short on a day to day basis, but this rainfall is usually in tense. Sunshine rates are stable the
47 throughout year, hovering between sevent y five and sixty percent (see Figure 6.4). The solar orientat ion is another major factor Tampa is located at approximately 28 north lati tude. The low latitude ma kes Tampa susceptible to near 90 sun angles during the summer m onths, but yet the sun angle wont reach 40 during a few days of the winte r months (see Figure 6.5). As for prevailing winds, there are a couple of fact ors at work. First, during the morning, the land heats up quickly. This rise in temperature causes atmospheric pressures to lower, thus allowing the c ool ocean air to move inland. This is known as an on-shore breeze. During t he night however, the roles are reversed. The ocean will be warmer and will have a resu lting off-shore breeze. The second component of the prevailing wi nds is the a jet stream. During the winter, the jet stream is far enough south to cause most Figure 6.4 Tampas possible sunshine range (rssWeather.com)
48 Figure 6.5 Tampas solar chart from June 21st to December 21st (University of Oregon) (Google Earth) days to have prevailing winds blowing in from the west to the southwest. However, the jet stream during the su mmer moves far to the north, and Tampa will be affected by a tropical flow which runs east to west. The result of the jet stream moving north allows light easterly winds to run west across Florida towards the Gulf Coast and the city of Tampa. Also, an on-shore breeze comes from the west during the day moves eas t. The collision of these two wind sources causes a convergence where they meet. Rain clouds will then form. This is why it rains nearly every day in Tampa during the summer (see Figure 6.6).
49 Figure 6.6 typical wind convergence (U.S. FAA AC) Other concerns include severe weat her and tropical cyclones. Florida is the thunderstorm capital of the world.23 The "lightning belt" in Florida is an area that extends west from Orlando to Tam pa, then south along the west coast to Fort Myers and east to Lake Okeechobee. Th understorms are attributed to hot, wet air close to the ground combined wit h an unstable atmosphere. Often the resulting thunderstorms occur during afternoons, predominantly from June through September. These storms can be as brief as a few minutes or as long as a couple of hours. Light ning is the state' s leading cause of weather-related deaths, and Florida has the distinction of having the nation's worst record of deaths by lightning.24 Finally, although it has been more than forty years since Tampa has been struck directly by a hurricane, the potential risk for such a storm always exists.
50 Knowing the climate conditions of a par ticular site is an important design consideration. Different weather phenomena can cause buildings to be less effective or even fail if the building is bu ilt for the wrong set of conditions. Given Tampas climate, this project will need to take measure to block direct radiant gain and shed water effectively, among other things. Surrounding Influences The most prevalent surrounding influenc es deal with the adjacent zoning and building uses (see Figure 6.7). The site is surrounded almost entirely by developed property. Perhaps the most thorough developm ent is along Franklin Street. Franklin Street has numerous small retail shops and small restaurants. One specific location along Franklin, the intersection with Zack Street, has two plazas carving out the northwest and sout heast corners. This creates a very pleasurable experience for those rela xing outside (see Figure 6.8 and 6.9). Along Twiggs Street, as with Franklin Street, many small cafes and shops dominate the street front age (see Figure 6.10). Perhaps the most intimate location along the Twiggs block is the Fr anklin and Twiggs intersection. On the south side of this intersection, the street is closed to vehicular traffic. This allows the two cafes on this intersection to engage the street (see Figure 6.11) In addition to the cafes, this intersection also has a historic building on northeast side, called The Franklin Exchange (see Fi gure 6.12). On north side of the site, Zack Street represents a devel oping block. Future grow th should be expected as
51 vacant retail under a new tower complet ed in 2007, called SkyPoint, has yet to be occupied (see Figure 6.13). In addition, a parking lot is for sale along Zack Street and the property is z oned for retail at the ground level. Besides the future development, two banks are located along Za ck Street in the adjacent blocks. Usage along Tampa Street is the least developed. This may be due to the fact that the street is one way and that vehi cles speed down this street (see Figure 6.14 and 6.15) Although not adjacent this site, further south along Tampa Street, more shops and cafes can be found. Figure 6.7 ground level usage (ima ge modified from Google Earth)
52 Figure 6.8 plaza on corner of Franklin Street and Zack Street (author photo) Figure 6.9 Franklin Exchange Plaza (author photo)
53 Figure 6.10 Twiggs Street s hops and cafes (author photo) Figure 6.11 Franklin-Twiggs intersec tion looking south (author photo)
54 Figure 6.12 Franklin Exchange (author photo) Figure 6.13 vacant retail under Skypoint at Zack Street and Tampa Street in tersection (author photo)
55 Figure 6.14 lack of development on Tampa Street (author photo) Figure 6.15 lack of development on Tampa Street (author photo)
56 Access Surrounded by streets and public si dewalks on all four boundaries the building will be able to be accessed from any side. The most common way people will arrive to this location, will be by car. Noting that both Zack Street and Tampa Street have one-way vehicular traffi c, and that Franklin Street prohibits vehicles south of Twiggs Street, only a few appropriate locations exist for the parking ramp into the project (see Figure (6.3). This parking ramp will have to accommodate both the entering and exiting of vehicles without causing traffic congestion on the streets. Mass transit access to the project site is fairly limited. The Purple Line does have a trolley stop on the west side of the site, but those using buses will have to walk a couple of blocks to get to the project (see Figure 6.16). Figure 6.16 right-of-ways of various travel methods (image modified from Google Earth)
57 Bike lanes and pedestrian right-of-ways are the remaining ways to access the site. A bike route runs along Ta mpa Street and public sidewalks surround the site. As stated, Frank lin Street south of Twiggs is closed to vehicles. Although hindering vehicular movement, th is closure results in a strengthened connection of the pedestrian right-o f-way along Fr anklin Street. Zoning Regulations Tampas city codes are the most ex tensive and complex in its central business district. Below is a listing of some of the most impactful codes that will be of great concern for this project.25 1. This district will contain co mpact, mixed-use development. 2. Structures shall be compatible with any signi ficant natural, historic or architectural resources in proxim ity to the projec t site. Examples of ways to achieve co mpatibility include desi gn features such as height-to-setback ratios or st epped or graduated building faces. 3. All buildings with a height in ex cess of one hundred (100) feet shall be equipped with a fire control sys tem approved by the city fire department. 4. Developments in the Central Business District (CDB) that propose a redevelopment of an entire ci ty block (excluding waterfront developments) under one (1) unified plan shall provide a minimum five-foot average building setback on all sides. The purpose of the
58 averaged setback is to accommodat e widened, pedestrian-oriented sidewalks and more functional open public space. The area created by the required building setback may be counted towards the open public space requirement as requi red and defined by this article. 5. The design of the parking stru cture and/or the design of the facades of parking structures whic h are incorporated in the building footprint, or which extend from the principal building component, shall be architecturally integrated. 6. The design of the parking struct ure must conceal vehicles from grade-level views. 7. The design of the parking st ructure must utilize landscaping elements or other design features to soften the appearance of the exterior facade. 8. All service and loading areas shall be effectively screened from pedestrian view. 9. The on-site parking requirement is one car per one thousand square feet of office space. 10. A major entry must be located along all retail that boarders the Franklin Street edge. 11. All uses along the Franklin Str eet frontage shall contribute to the active pedestrian character of the corridor and shall include retail, personal services, and public facilities.
59 12. A minimum depth of twenty (20) feet, as measured from the building line along the entire Frank lin Street frontage, shall be provided for these uses. 13. All spaces fronting on Franklin St reet shall locate a major entrance onto Franklin Street. 14. All spaces fronting on Franklin St reet (and where feasible in major renovations) shall be visible from Franklin Street by devoting not less than fifty (50) percent of the ground level facade plane to transparent material. 15. The design of all new structures shall maintain at least eighty (80) percent of the building line at the property line along Franklin Street. 16. Ground floor parking which front s on Franklin Street in parking garages is prohibited al ong Franklin Street.
60 CHAPTER 7 OFFICE BUILDINGS WITH SELF CONTAINED PARKING Introduction One of the key aspects of this project is choosi ng a site with no special advantages concerning the urban heat island. For that reason a small site in middle of a downtown Tampa has been chos en. In addition, with consideration of economic factors, the project will need to be high de nsity in nature and have self-contained parking within t he building. Proper attent ion must be paid on how a building with these components functions This chapter will examine these types of buildings and it hopefully will s how how design strategies for the heat island can be incorporated into this typical office building. The analysis conducted, focuses on three buildings in do wntown Tampa. These buildings are: 501 Kennedy Boulevard, The Franklin Exchange and Park Tower Parking One of the biggest issues with downto wn office building, especially in Tampa, is parking. Parking can determi ne whether a project succeeds or fails.26 Currently Tampas downtown minimum par king spaces per office square footage
61 is one space per thousand square feet.27 However, the minimum amount is far below what tenants expect if they are to lease downtown office space. Of the buildings analyzed, the parking spaces per office square foot was close to the minimum. Park Tower has just over one per thousand square feet. 501 Kennedy has 1.3 parking spac es per thousand square fee t. Finally, the Franklin Exchange has roughly 1.5 spaces per thousand square feet. The building managers, Michelle Cummings of 501 K ennedy and Mary Ayo of Park Tower, both expressed problems in securing tenants due to limited parking. They lose many tenants to Tampas Westshore Dis trict because that landlords in that district can offer all the parking the tenants need.28 Both Cummings and Ayo feel that any new building in downtown Tampa should at least try and achieve a 1.5 parking spaces per thousand square feet of o ffice space. Anything less might be an unsuccessful venture. Another issue with parking downtown is where to locate parking within the program of the building. All three buildings analyzed had parking begin on either the second or third floor and was sta cked together above that. In some instances, the parking levels were also parti ally sectioned off to provide room for mechanical space. For example, Park Towers fifth and sixth parking floors where partially occupied by the HVAC equipment. In gener al, a parking level comprising an entire downtown Tam pa block can achieve around 100-130 parking spaces. This is the case fo r both 501 Kennedy and Park Tower. The Franklin Exchange however, achieves ar ound seventy spaces per floor with
62 parking level taking up nearly half the blo ck. Refer to figures 7.1-7.3 for the parking layouts of each of these towers. Figure 7.1 501 Kennedy Boulevard. parking is shown in grey, office space in red, retail in orange and mechanical in light blue. (author diagram) Figure 7.2 The Franklin Exchange. parking is shown in grey, office space in red, retail in orange and mechanical in light blue. (author diagram)
63 Figure 7.3 Park Tower. parking is shown in grey, office space in red, retail in orange, mechanical in light blue, restrooms in blue and elevator lobbies in dark grey. (author diagram) The parking entry is another concern. Since parking is located above the ground floor, the building must provide a ramp to take vehicles up as soon as possible. Doing so will prevent wasting va luable ground floor space. This is the case for all three of the analyzed build ings. However, there are slight differences. The Franklin Exchange for inst ance, is the only building of the three
64 that has a separate entry and exit for its parking garage. The 501 Kennedy building has a ramp that runs through the center of the building all the way to the third level. And, Park Towers entr y condition is unique because it is very unpronounced from its location on Ta mpa Street (see Figure 7.4). Finally, is the issue concerning the par kings architectural integration into the building as a whole. All buildings along the Franklin Street must adhere to the Tampa Central Business District Urban Design Guidelines. These guidelines state that the exterior faade of parki ng levels along Franklin Street must be architecturally integrated.29 The code also requires landscaping features or other design elements to soften the appearance. One example of this is at Tampas new condominium SkyPoint (see Figure7.5). Figure 7.4 parking entry and exit to Park Tower (author photo)
65 Figure 7.5 design elements on SkyP oints parking garage (author photo) Building Core and Leasable Office Space Another important issue concerning th is type of office building is the building core. It is important that the building core be situated in a way that allows for maximum flexibilit y for the office floors. A speculative office building needs to maximize leasable office space while minimizing its core functions. There should also be few interior obstr uctions. Both the 501 Kennedy and Park Tower have bay sizes around thirty feet by thirty feet. The main goal, however, is to was the maximization its office space s quare feet ratio to core square feet. A high office space to core ratio can be ac hieved if the vertical circulation and
66 mechanical system can be centrally locat ed. Grouping these functions centrally in a core is common for tall buildings.30 Not only will the core serve as the buildings vertical circulation and mechani cal spaces, the building core can also act as a resistance to wind and other st ructural loads. Park Tower houses both of its elevator banks, two stairwells, re strooms and the mechanical rooms in this core (see Figure 7.6). As Park Towe r continues up, one bank of elevators discontinues on the twenty-fifth floor (see Figure 7.3). At this level, Park Towers floor plan changes. The restrooms and mechanical room have are relocated over the elevator shafts and elevator bay below. The room adjustment opens up additional office space for the towers upper floors. All together, Park Towers twenty-eight floors of office space aver age over 14,000 square f eet per floor for a Figure 7.6 Park Towers fourteenth floor. cyan is office space, red is elevators, blue is restrooms, grey is stairs, magenta is non office corridors, white is service (provided by Mary Ayo)
67 total 500,000 square feet of leasable office space. Each office level of the tower has roughly eighty-two percent of the square footage dedicated to the office space. The building core functions and layout for 501 Kennedy is slightly different. Perhaps the biggest difference that affects the core is in the design and location of the mechanical space at the top floor. 501 Kennedy, unlike Park Tower has its air handler on this floor. This location a llows each floor to be less consumed by air handler rooms. 501 Kennedy has a 5 foot chase for all of the mechanical piping (see Figure 7.7). Another slight difference is the way 501 Kennedy leases office space. The shared hallways in Pa rk Tower are considered leasable, where as in 501 Kennedy they are not. The shared hallway square footage in the Colonial is divided among the tenants t hat share that particular floor. Figure 7.7 501 Kennedy various office floors (author diagram)
68 Ground Level Program The final key component of these offi ce buildings was the program at the ground level. First, 501 Kennedy has a small back of house consisting of a security room, trash room, mail room, and fi re control room. Two stairwells from the core make their way out to the str eet via fire-rated corridors. The program also includes a lobby with an adjacent elevator bay and information deck. A unique vehicular path runs thru the bu ilding, and also functions as a porte cochere (see Figure 7.8). Adjacent to t he vehicular passage is the parking entry and the ramp. This ramp continues all the wa y up to the third floor. The rest of the program is then dedicated to retail space. Figure 7.8 porte cochere at 501 Kennedy Boulevard (author photo)
69 Second, Park Towers is similar in it s first floor program. Retail makes up the largest component of first floor. A lobby and large interior hallway slices thru the center of the bu ilding. The core consists of mechanical space, two elevator shaftways and two stairwells. Adjacent to the core is the information desk, which overlooks both elevator lobbies. A loadi ng dock is located on the first floor within the building and has adjacent maint enance rooms and a security room. Third, The Franklin Exchange is quite a bit different from these two. Only a small portion of its first floor is taken up by retail space (see Figure 7.9). Only the southeast corner is usable for retail or of fice space. The rest of the first floor is taken up by the typical stairs, lobby and el evator shafts. The main culprit in the loss of retail space is the mechanical room being located on the ground level. Figure 7.9 The Franklin Exchange ground level (author diagram)
70 Conclusion Designing a building that succeeds in combating the urban heat island but fails in providing a functional program is a failed building. Current buildings in downtown Tampa show, the basic steps in achieving a functiona l program. The buildings detailed were in many cases us ing similar strategies when formulating the vertical and office program. Using the ideas garnered her e, it will help to anchor basic design concepts and layouts for a new building.
71 CHAPTER 8 PROGRAM Introduction A project within Tampas urban core presents a unique programming challenge. Buildings located in t he downtown area shoul d seamlessly blend a variety of functions within a constrai ned area. In addition, many local codes restrict the functions at the ground or street level. By these codes, the ground level perimeters should be pedestrian friendly and have easy access for all building users. Likewise, service func tions should also be easily accessed by utility personnel. Parking restrictions also affect programming decisions. Buildings in the downtown cores require nea rby or onsite parking in order for the buildings to be successful. Buildings in the urban core are among the most challenging buildings to program due to the afor e mentioned factors. Goal and Objectives The prime program goal for this pr oject is to house and integrate the unique characteristics of three different building use types, while minimizing the heat gain on the buildings exterior and r oof. The three primary usage types are
72 office, retail and a parking structure. In accordance with other buildings in downtown Tampa, the best way to layout t hese unique functions is to place retail at the base, parking above the retail levels and office space in a tower (see Figure 7.1 7.3 and 8.1). Secondary pr ogram goals include a vibrant pedestrian street level environment and a rooftop terrace with an adjoining restaurant. These goals meet the citys vision of downtown Tampa. To accomplish this, the building must contain several features. Due to being adjacent to the pedestrian mall along Franklin Street, retail will play an important role on the east side of the building. Franklin Street is an important retail artery in the downtown area and enjoys a unique blend of retail shops and rest aurants, both south and north of the project site. Although parking along Franklin Street is limited for the retail, the street has become a very pedestrian fr iendly corridor as the speed limit is reduced and traffic is prohibited in some locations just south of the site. Figure 8.1 vertical program layout of a typi cal downtown office building (author diagram)
73 Cultural Issues A special issue regarding the project is the adjacent location of the citys Cultural Arts District. The Cultural Ar ts District encompasses the main Tampa Public Library and the Tampa Bay Perfo rming Arts Center. In addition, the Tampa Art Museum and Childrens Mus eum are currently under construction (see Figure 8.2). These nearby features should give the project a unique identity and cultural significance. In addition to the cultural buildings, the downtown area also places an emphasis on Franklin Street as a cultural corridor. As stated, Franklin Street is a very pedestrian fri endly. The street has unique signage, places to sit, landscaping features and spec ial lighting. Howeve r, these features remain underdeveloped at the project si te and represent a void in Franklin Streets overall makeup. Zack Street, which is the nor thern boundary of the site, has a growing cultural importance. Za ck Street connects the Tampa Theater to the two museums under construction and to t he waterfront as well. Zack Street runs east west and intersects Franklin St reet. The cultural importance of Zack Street has been steadily grow ing and the street will become ever important once the Childrens Museum and Tampa Art Museum are completed.
74 Figure 8.2 cultural features (image edited from Municode)
75 Public Transportation Currently only one public transportat ion line has adjacent access to the project site. The In-Town Trolleys Pu rple Line has a stop on Tampa Street (see Figure 8.3). The Purple Lines main s ource of pedestrian usage comes from Harbour Island to the south. Those liv ing at Habour Island and using the Purple Line would exit the trolle y onto Florida Avenue in the morning and enter back on the trolley from Tampa Str eet in the evening. An ad ditional source of public transportation may originate from the Marion Transit Center located just north of the downtown area. Those usi ng this center can then eit her take the Purple Line or the Marion Street Transit Parkway. The building programs exterior accessibility should reflect thes e public transportation methods. Parking Parking for the 610 Franklin Street Bu ilding is another ma jor issue. As with other office buildings in the downt own area, parking must be located near the site or on the site. For this projec t, parking will need to be located on-site for this location as no adjacent public parking lots currently exist (see Figure 8.3). For this reason, attention should be placed on developing a well integrated parking garage within the building.
76 Figure 8.3 downtown Tampa public transportation and public parking locations ( www.tecolinestreetcar ) Vehicular Functions In addition to the program location of the parking, other vehicular issues will need to be addressed. Perhaps most crucial is the amount of parking needed. Currently the code requires t here to be one parking spot per one thousand square feet of net office space. These spots are then generally given to the leasee based on the total of squar e footage leased. Visitor parking, as with most downtown buildings, should be located on the streets and in public parking garages within the downtown area. Since no nearby public garages
77 exist, the project may need to include additi onal on-site parking for the retail establishments to be successful. In additi on, if a rooftop restaurant is located within the project, it will also require additi onal parking. As for service vehicles, a single loading bay may be appropriate. Both Park Tower and 501 Kennedy have a loading bay at the grade level. Both of these loading bays were separated from the private parking ra mp entrance. Time Use (Daily, Weekly and Annual Cycles) The 610 Franklin Street Bu ilding should have full acce ss to the building lobby during the normal business day. Employ ees, customers and deliveries will be very frequent throughout the day. In par ticular, the morning rush, noontime and evening rush will experience increased traffic flow. Areas where pedestrian traffic intersects, design considering wil l need to be taken so that proper egress and life safety requirements have been acc ounted for. Areas where pedestrians can linger should be provided with seating and focal points where people can easily gather. The retail space along the street will experience its most pedestrian traffic during the noontime rush. Since the daytime heating is most prevalent during this time, the reta il area should be provided with adequate. shading to allow for optimal outdoor co mfort. During the weekends, when less pedestrian traffic is expected, the env ironment should be conducive to draw people to the retail area along the Franklin St reet corridor. As for annual cycles, the summer months will be of the greatest concern. The temperature in Tampa
78 during the summer months average between 85 and 90 degrees. Providing shading during these months may not be enough to provide an appealing atmosphere. Tampa City Center, loca ted a few blocks south out the site, combines structural shading, tree shadi ng and water features to lessen the ambient temperature (see Figure 8.4). The Tampa City Center model is one desirable way to combat Tampas adverse summer conditions. Figure 8.4 Tampa City Ce nter (author photo) Exterior spaces As stated in chapter 5, the summer months in Tampa are hot and humid. For this reason, exterior patios and terraces should be covered in the downtown area. These outdoor patios and terraces should be well shaded, whether by vegetation on construction elements. Sinc e most of the activity outside will be
79 from retail patrons, a prot ected and comfortable atmo sphere should provide a more pleasurable shopping and leisurel y environment. In addition, Tampas summer months will often ex perience brief periods of intense downpours in the evening. Any successful evening outdoor use wil l have to take this into account. Landscaping requirements Vegetation on the site should be used at grade level, building terraces and perhaps on the facades as well. Trees located above the grade level must have adequate support and spacing to allow for natur al growth. They also must be easily accessed by maintenance staff as they will need to watered and pruned on a regular basis. The species of vegetation chosen should relate to vegetation surrounding the 610 site and should be native to the Tampa area to minimize irrigation needs. Some attention should be taken to use building water runoff to fill the watering needs of this vegetation. For the facades, if vines are chosen, care and choice of material must be considered. The facades must be able support and facilitate the growth of these vegetation types. Circulation Issues Circulation issues should be a focus on Franklin Street. There should be adequate entry locations for businesses along this street as well as a well coordinated way to get to the retail patrons on the second level. This will allow
80 for additional retail on Franklin Street. Circulation should be open to the public in most cases, while having limited access to the back of house spaces reserved for security, utility and maintenance personnel. The outdoor areas should be protected from the weather in areas wher e pedestrian traffic is most pronounced. As a whole, the circulation should be easily navigated as not to create a labyrinth of corridors or alleyways. Separate Access Requirements Other than the main lobby access, there will need to be additional access points around the building. Secondary a ccess to the lobby will almost certainly be necessary if the building has a centra l core. The code restricts dead end corridors to 20 feet, so if t here is a central elevator bay two means of exit must be provided. For delivery and utility entry, direct access can be located along the street or it can be accessed through a load ing bay. For a loading bay, it could be either connected directly to the str eet or could be accessed through the parking garage. There will also have to be street access to all ground level retail shops. If retail is to be located on the second floor as well, either elevators, stairs or even escalators may be necessary to provide the essential accessibility requirements.
81 Sustainability Issues and Requirements Project sustainability issues will be a priority concern for this project. The program must be able to compliment the i ssues of limiting heat gain. Vegetative facades and roofs is one program factor t hat will play an impor tant role in the layout and interrelationships of the interi or spaces. The building skin, in those areas that are not vegetat ed, will need to be designed in such a way to either vent or cool the air space directly adj acent to the buildings envelope. Any program relationship that contributes to heat gain or adds to the generation of unnecessary waste heat is not desirable. Security Issues and Requirements Security issues that may affect the sites program will involve the location of the security office. The nearby Tam pa building, Park Tower, has a security office at the ground level. The room is located in the back of house area but has several connections to the interior lobby and adjacent corri dors. In addition, the security staff at Park Tower also runs the information desk flanking the elevator bays. The location allows secu rity staff to observe all incoming and outgoing pedestrian movement at the ground level. The 610 Franklin Street Building should follow these basic guidelines when addressing securitys program location
82 Solid Waste Collection Waste collection should not block ci rculation. The waste should be collected on the ground level in a closed access room. The room should have adjacent access to the loading dock. The loading dock should then have access to the street, preferably a street that has less emphasis on the pedestrian environment. Waste collection within the office tower will be done floor by floor. A janitorial room on each floor will be require for this type of waste removal. As with Park Tower and the 501 Kennedy Bu ilding, this waste will be collected during the afterhours to avoid con gestion with the building employees. Adaptability and Flexibility Issues 610 Franklin Street should have a flexib le office space arrangement. Park Towers building manager, Mary Ayo, ex pressed that having office space surrounding the elevator core is easier to lease out. This type of floor layout allows leasers more ability to expand on a floor and even add floors. Ms. Ayo also expressed that bay sizes were import ant as well. She stated The larger the bay size, the more flexibility a new client has in designing their office layout. For the reasons Ms. Ayo expre ssed, 610 Franklin Street Building should have a comparable bay size and a central core.
83 Day lighting Requirement s for Occupied Spaces All the office floors at 610 Franklin St reet should have ex terior windows. On the south sides of the building, where light is ample throughout the day, strategies should be explored in order to r educe glare. At the same time, it will also be beneficial to bounce light far back in to the occupied space. For example, a well placed light shelf could reduce the overall lighting needs of a space, thus reducing the generation of wa ste heat for the building.(s ee Figure 2.16 and 2.17) The east and west exposures of the build ing, although affected by sunlight for shorter periods of time, will be affected with the worst glare. This is due to the fact that the suns ray will strike t he building more on a horizontal angle. Mechanized vertical louvers may be most effective in controlling this type of natural light condition. In addition me chanical louvers can be opened to allow ambient light to enter when the sunlight no longer strikes its surface. HVAC systems Due to size of the project, large c onsiderations and allocations of space must be given to the HVAC system. From research obtained on nearby buildings, a cooling tower, chiller and air handlers will be needed. Air handlers should be located on each floor, at a centra l location, to reduce the need for large vertical ducts moving through the building. Then, either a dropped ceiling or an access floor system can provide all the air movement needs for each office level.
84 Chilled water should be pumped to each floor thru a vertical shaft. The cooling tower, which removes heat from the chilled water system, will need to have adequate ventilation and should be located away from the out door restaurant and other areas used by building patrons and employees. Other Mechanical Systems Electrical, plumbing, communications and fire protection systems will all need to be run vertically thru the build ing. Although the space needed will be much less than the HVAC system, some s pace will need to be allocated on each floor. The review of other downtown offi ce buildings in Tampa shows that the best place for these systems is to locate them at the building core. Mechanical systems located at the building core prevent the removal of valuable outer office space. In addition to these vertical spaces, distribution rooms for each system will need to be located within the building. Nearby Park Tower places each of these systems in a corner of the park ing garage. 501 Kennedy locates these distribution systems on the first floor. Yet, the Fr anklin Exchange locates a majority of them in the basement. Regar dless of where the location will be, the noise level for some of these systems mu st be taken into account and access for maintenance crews must be considered.
85 Table 8.1 typical office floor program (author table) Table 8.2 ground floor program (author table)
86 Figure 8.5 typical floor layout (author diagram) Figure 8.6 vertical adjacency diagram (author diagram)
87 a a a CHAPTER 9 GOALS AND OBJECTIVES This thesis project deals with architectu ral strategies in reducing heat gain in the sub-tropical urban heat island. The goal and objectives of this project must compliment the problems identified. T he following is a series of key design considerations and suggestions that shoul d be resolved to provide a successful solution to this problem. First, this project will need to provide a developed exterior envelope that reduces the heat gain on building. The env elope should not only limit direct heat gain onto the building but should also use materials and strat egies to reflect away heat gain and prevent the heat from co nducting into the building. Whatever the method, the envelope should be economically feasible. Second, this project should incl ude a developed gr een roof system. Although tall buildings will have a majority of its surface area located on the elevations, roofs will still be a substantia l components of the buildings exterior envelope. In addition, t he green roof system should hav e complete or partial access to the public as these green spaces can add to the human health qualities in t he urban center.
88 Third, the project should provide an environment at the st reet level that can add to the ambience to the downtown area. The street level should provide relief from oppressive and in clement year round. The street level should also incorporate the citys intentions and vision for Franklin Street. Fourth, the project should provide a high usable office space to building space ratio, plentiful parking, and additi onal amenities into the program. The project must be plausible in layout and in price so that it could theoretically compete for the citys best tenants in leas ing out its office space. The project may still be among the highest for compar able cost within the city, but its amenities must justify this considerable cost inflation.
89 CHAPTER 10 DESIGN PROPOSAL Figure 10.1 office tower proposal (author model)
90 I ntroduction The design of this project takes into account the strategies and techniques determined to be most appropriate to r educe or lesson the impact of the heat island effect and to lesson or eliminate its own contribution to the heat island already present. Some of the strategies th is project entails are: the use of green roofs, the orientation of the building, the development of faade specializing and individualizing, the use of light shelves and vertical sun-shades, the implementation of a double wall faade and t he use of reflective light colored surfaces. Orientation and Site Layout One of the key problems wit h the site location, is that the site is square and located among many other skyscrapers (see Figure 10.2 -10.4). As stated in chapter two, a building in a hot climat e should limit its east and west exposure. For this reason the building tower abov e the parking garage has been orientated to have four office bays facing south and north, and three office bays facing east and west (see Figure 10.5). In addition, the north faa de has two additional half office bays pulled from the building. See Figures 10.6-10.12 for all plan types.
91 Figure 10.2 site model (author)
92 Figure 10.3 and 10.4 site model (author)
93 Figure 10.5 tower orientation (author)
94 Figure 10.6 first floor plan (author)
95 Figure 10.7 second floor plan (author)
96 Figure 10.8 third floor plan (author)
97 Figure 10.9 fifth floor plan (author)
98 Figure 10.10 ninth floor plan (author)
99 Figure 10.11 twelfth and twenty second floor plan (author)
100 Figure 10.12 twenty fifth and twenty ninth floor plan (author)
101 Faade specialization and optimization Perhaps the key component of this pr oject is the use of three different faade types for the office tower. The o ffice tower component of this project runs from ninth floor to the thirty-sixth floor This expanse makes the office tower portion of the project the la rgest percentage of buildi ng surface area. Through the research, it was found that the qualit y and type of light energy hitting the building vastly differed. The north faade, for instance, had little to no direct light. The west and east facades suffered from low altitude light and had a variable azimuth. Yet the south had light originat ing from a high altitude and a constant azimuth. A light study was conducted at various time s to see what techniques should be implemented (see Figures 10.13-10. 18). The key differences of the facades include: types and sizes of louvers and light shelves used, introduction of a double wall system, thickness of the wall, and added ventilation shafts within the double wall to carry away ambient heat. Figures 10.19 10.26 show additional details of this system.
102 (left) Figure 10.13 south interior, noon 6-21 solar al titude = 85 degrees solar azimuth = 0 degrees (author) (right) Figure 10.14 west interior, 3pm 6-21 solar al titude = 45 degrees solar azimuth = -5 degrees (author) (left) Figure 10.15 south interior, noon 9-21 solar al titude = 62 degrees solar azimuth = 0 degrees (author) (right) Figure 10.16 west interior, 3pm 9-21 solar al titude = 38 degrees solar azimuth = 25 degrees (author) (left) Figure 10.17 south interior, noon 12-21 solar al titude = 38 degrees solar azimuth = 0 degrees (author) (right) Figure 10.18 west interior, 3pm 12-21 solar al titude = 23 degrees solar azimuth = 45 degrees(author)
103 (left) Figure 10.19 south elevation (righ t) Figure 10.20 west elevation (author)
104 Figure 10.21 south faade tower section (author)
105 Figure 10.22 north faade tower section (author)
106 Figure 10.23 double wall system, west and south fa ade. west faade with vertical louvers (author)
107 Figure 10.24 double wall sy stem vent stack (author)
108 Figure 10.25 north-south building se ction showing overall shading (author)
109 Figure 10.26 retail level section model (author)
110 Green Roofs As detailed in chapter 3, the urban forest contributes to the reduction of the heat island through reducing direct r adiant gain and the transfer of energy through evapotranspiration. This design pro posal incorporates four roof gardens and carves out a courtyard at the grade level for additional tree canopy coverage. Although the amount of tree canopy cover age is much less than in rural areas, the incorporation of roof gardens where allowable is a necessary component in the reduction of the heat island. Thr ough the design process it was a standard notion that any terminating volume of the tower would feature a roof terrace or garden at the top (see Figures 10.6, 10.9, 10.10, 10. 12 and 10.27-10.28) Figure 10.27 entry plaza (author)
111 Figure 10.28 model showing r oof-top garden locations (author)
112 Additional Graphics of Design Proposal Figure 10.29 site rendering (author) Figure 10.30 tower perspective (author)
113 Figure 10.31 model showing east faade (author)
114 Figure 10.32 model showing south faade (author)
115 Figure 10.33 model showing west faade (author)
116 Figure 10.34 model showing north faade (author)
117 CHAPTER 11 SUMMARY Introduction The intent of this project is to show that the implementat ion of strategies and design features in a building can reduc e the heat island effect, even the most challenging area. The ar ea and building type selected for this project had no inherent advantages over any other typical site or building typology. In addition, it was important for this project to show that the design implementations were effective and inexpensive. This final c hapter will look into cost analysis data, energy analysis data and give suggestions on what should be done for future projects within a downtown setting. Cost Analysis Any new office buildings within the Central Business District in Tampa must have competitive rental rates against other similar office space in the area. If this is not done the project will either fa il or never be built. Additionally it is necessary to provide certain amenities to meet certain office classifications. Some of the data needed to conclude if this project is viable are: the average
118 rental rates of a downtown Tampa building, the rentable space within this project, the operational expenses to service a buildin g, the cost to build a similar building and a cost projection for this project. First, this project encompasses roughl y 413,000 square feet of office space and 40,000 square feet of retail space. The cost to construct this proposal came out to $77,000,000 (see Appendix A). The cost analysis was derived from a program called DProfile developed by Beck Technologies. Using the same program, it was predicted t hat the energy needs of t he building would be $9.95 per square foot over a fift een year period. Based on these numbers, the rental rate before the inclusion of a profit margin and personnel costs, came out to $21.95 per square foot. Second, according to the online publication Collier Arnold the average class A rental space in downtown Tam pa was $23.45 a square f oot in September 2008.31 based on these numbers it is plausib le to assume that this project proposal is viable considering construction feasibility. Energy Analysis A second important component of this pr oject is to show that the proposed project will have a reduced impact on the heat island effect. Unfortunately, two components of the heat island effect, di rect heat gain and ambient heat are difficult to model using computer software. Howeve r, programs like DProfile from Beck Technologies can show the reduc tion of waste heat by modeling a
119 buildings energy consumption. As descr ibed in chapter two of this document, the reduction of waste heat has a dire ct relation with both the reduction of ambient heat and direct heat gain. So if a building can reduce its own total energy consumption, it will likely limit its own direct heat gain and will reduce the locations ambient heat. To show the buildings energy cons umption was lowered due to design strategies, a cost comparison analysis was done. The cost comparison analysis comprises of three studies (see Appendices A-C for complete an alysis). The first is a study of the proposed project as is The second is the same project but substitutes the building skin of a double wa ll system for a full glass curtain wall. The third is the same as the first study but with the project rotated ninety degrees clockwise. Careful analysis between study one and tw o shows thats a building that takes into consideration the effects of di rect heat gain, costs considerably less and uses less energy (see Figure 11.111.3). The inherent advantage of a double wall is reduction of direct heat gai n on the building. The reduction of direct heat gain allows a building to reduce its air handling needs. On the reverse end of the spectrum, a glass curt ain wall building does not address direct heat gain at all. This is why the data shows that the air handling needs between the two skin types is five hundred tons for the same building, a cooling load reduction of twenty-five percent. Bec ause of the reduced air handling needs, electrical use in the building drops over ten percent. During a fifteen year life span of the mechanical syst ems from initial purchas e and year to year
120 operational costs, a savings of 1.6 milli on dollars can be expected based on the projections. A similar comparison can be drawn up on a buildings orientation. As stated in chapter two, a bu ildings form and orientation can help lower heat gain. A building in a hot humid climate typi cally should be orientated to limit sun exposure on the east and west. Study one, the project proposal, has the tower orientated with four bays facing south and three bays facing east/west. Study three is the opposite. By analyzing the dat a from these two studies, this simple move proved to be cost effective for t he proposed project (see Figure 11.1-11.3) Study one lowered the air handling needs by fi fty-eight tons over the less optimal study three. The result is an energy and monetary savings as well. Figure 11.1 electrical use (graph using data from DProfile)
121 Figure 11.2 peak building load (graph using data from DProfile) Figure 11.3 life-cycle costs (graph using data from DProfile)
122 Energy Recovery Analysis One additional development deals wit h the energy that can be recovered from the HVAC systems. Although not architectural in nature, energy recovery systems can play a significant role in t he reduction of waste heat. As covered in chapter four of this document, one type of energy recovery system is a rotary enthalpy wheel. These wheels transfer ener gy stored in building exhaust to the fresh incoming air. These system s can be quite large and should be appropriated for early in the design process. A computer model was run to see if such a system would be effective for this project (see Appendix D for complete results). The results data concluded t hat using an enthalpy wheel would reduce the total cooling load by twenty-five tons Although this is only a reduction of two percent of the total load capacity, the r eduction will save on energy year to year and total initial mechanical cost would be reduced as well. Conclusion The urban heat island contributes too many negative effects on its inhabitants and to the environm ent. Many cities are in dire need to change its urban make-up to lesson these negative e ffects. Unfortunat ely, construction companies have been slow to come to terms and have avoided various methods detailed in this document for fear of incr eased costs. Through the process of this thesis, it is clear that mu ch can be done to reduce the effects of the heat island in
123 the urban setting while still reduc ing costs. Things as simple as positioning the building along the correct axis have a significant impact on mechanical and lighting needs. Constructi on of a double wall, like that of the New York Times tower can have higher up-front costs but will reduce life-cycle costs through lower energy needs. Even just the dedication of fifty additional square feet for an energy recovery system can recoup its ow n cost within a year or two through energy savings. Regardless of the methods used, there is st ill much that can be done to create an impact on the urban heat island effect.
124 xSpace xSpace xSpace REFERENCES 1 Dale Fuchs, "Spain Goes Hi-Tech to Beat Drought," The Guardian 28 June 2005. 2 The Heat Island Group ed. Sheng-chieh Chang, 30 August 2000, Berkley Lab, 6 June 2008
125 11 Lloyd Alter, San Francisco Federal Building, Design and Architecture 9 March 2007. 12 Randy Shaw, San Franciscos Green Building Nightmare, BeyondChron 3 March 2008
126 23 Top 10 of the Most Dangerous US States for Lightning Deaths, About.com ed. Rachelle Oblack, 2008, The New York Times Company, 2 June 2008
127 Sxpace xSpace xSpace BIBLIOGRAPHY About.com 2008. The New York Times Company. 2 June 2008
128 Colliers Arnold. Ed. 2008. Tampa Bay Office Market Executive Summary. Market Research . 1 October 2008.
129 Oke, T.R. The Energetic Basi s of the Urban Heat Island. Quarterly Journal of the Royal Meteorological Society 1982 pp 1-24. Post, Nadine M. Owner is Radi ant about Lobbys Radiant Cooling. Engineering News record 1 October 2007: 15-16. Reflective Insulation Ed. 2005. Environmentally Safe Products. 6 June 2008
130 Xetex Inc. Ed. 2008. Enthalpy Wheels. 8 November 2008.
132 Appendix A: Energy Analysis One Figure A.1 project proposal cost analysis (DProfile)
133 Figure A.2 project proposal cost analysis (DProfile)
134 Figure A.3 project proposal energy analysis (DProfile)
135 Figure A.4 project proposal energy analysis (DProfile)
136 Figure A.5 project proposal energy analysis (DProfile)
137 Appendix B: Energy Analysis Two Figure B.1 alternate 1 project pr oposal cost analysis (DProfile)
138 Figure B.2 alternate 1 project pr oposal cost analysis (DProfile)
139 Figure B.3 alternate 1 project prop osal energy analysis (DProfile)
140 Figure B.4 alternate 1 project prop osal energy analysis (DProfile)
141 Figure B.5 alternate 1 project prop osal energy analysis (DProfile)
142 Appendix C: Energy Analysis Three Figure C.1 alternate 2 project proposal cost analysis (DProfile)
143 Figure C.2 alternate 2 project proposal cost analysis (DProfile)
144 Figure C.3 alternate 2 project proposal energy analysis (DProfile)
145 Figure C.4 alternate 2 project proposal energy analysis (DProfile)
146 Figure C.5 alternate 2 project proposal energy analysis (DProfile)
147 Appendix D: Energy Recovery Ventilator Data Figure D.1 energy recovery wheel data (Cook)
148 Figure D.2 energy recovery wheel data (Cook)
149 Figure D.3 energy recovery wheel data (Cook)
150 Figure D.4 energy recovery wheel data (Cook)
151 Figure D.5 energy recovery wheel data (Cook)
152 Figure D.6 energy recovery wheel data (Cook)