Hot and Humid Climate Zoning

Hot and Humid Climate

Urban Residential Zone

JEOS OREAMUNO

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Urban Residential ZoneResponse to Hot and Humid Climate

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Table of Contents

ARTICLE 1. Hot and Humid Climate

1.1 Climate Zones 1.2 North America 1.3 Heat Flow 1.4 Thermal Criteria

ARTICLE 2. Building Envelope

2.1 Design Criteria 2.2 Building Layout 2.3 Building Orientation 2.4 Building Elevation 2.5 Building Openings 2.6 Building Materials 2.7 Urban Density

ARTICLE 3. Zoning Regulation

3.1 Stories 3.2 Siting 3.3 Lot Coverage 3.4 Dwelling Units 3.5 Setbacks 3.6 Parking

ARTICLE 4. Sustainable Elements

4.1 Podium 4.2 Ventilation 4.3 Rainwater Harvesting 4.4 Terrace Garden

ARTICLE 5. Design Standards

5.1 Zoning Table

ARTICLE 6. Diagrams

6.1 Section Diagram 6.2 Plan Diagram 6.3 Axonometric


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ARTICLE 1. Hot and Humid Climate

1.1 Climate Zones Hot and Humid regions are divided into two categories; equatorial and tropical-marine regions. Both have similar temperature, humidity, and rainfall conditions but are different in their wind conditions. In coastal regions, the constant heating and cooling patterns of the sea and land areas create regular sea breezes, providing regular air motion and mitigating the heat stress, mainly during the afternoon hours. The tropical-marine region utilizes the trade winds blowing westward. The path of the trade winds moves north and south with the annual shift of the sun’s declination. In the equatorial regions precipitation is caused mainly by rising convection currents of moist air, resulting from the convergence of the trade winds at the equatorial zone, after passing over extensive ocean areas. This flow pattern leads in many areas to a regular pattern of afternoon rains, often accompanied by violent thunderstorms.

1.2 North American In North America tropical-marine climate affects the eastern half of Texas, Oklahoma, Louisiana, Arkansas, Alabama, Mississippi, North Carolina, South Carolina, Tennessee, Georgia, Kentucky, Florida, Virginia, and West Virginia. Humid subtropical climate can also be found in the Mid-Atlantic, primarily Maryland, Delaware, the District of Columbia, southeastern Pennsylvania, southern New Jersey and southern parts of New York, specifically New York City and parts of Long Island. Summers in this zone are hot and humid, with daily averages above 77°F with average daily maximums above 86°F.

1.3 Heat Flow

Moisture flows from areas of greater concentration to areas of lesser concentration. Buildings experience heat gain from the environment in three principal ways. In convection, heat is exchanged between a fluid (typically air) and a solid, with air flow playing a critical role in the extent of heat transfer. In conduction, heat is transferred directly within or between materials, with material density playing a critical role in the extent of heat transfer. In radiation, heat flows via electromagnetic waves from hotter surfaces to cooler surfaces. Moisture flow through envelopes is the principal means of latent heat gain.

1.4 Thermal Criteria

The U-Factor expresses the steady rate at which heat flows through a building envelope assembly and are commonly used in the built industry to specify envelope’s thermal design criteria. U-factors are calculated for a particular element (roof, wall, etc.) by finding the resistance of each material, including air space, then adding the resistances to obtain a total resistance. The U-factor is the reciprocal of the sum of the resistances. The result is an overall coefficient of heat transfer, and includes the effects of all sensible modes of heat transfer (conduction, convection, and radiation).

1. Humid SubTropical Climate

2. Monthly Diurnal Averages

3. Direct Solar Radiation

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°C W/m²MONTHLY DIURNAL AVERAGES - Miami, Florida - USALEGEND

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Comfort: Thermal Neutrality

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ARTICLE 2. Building Envelope

2.1 Design Criteria

The design objectives should be to modify the indoor climate in order to improve the comfort of the inhabitants, reduce the energy consumption of the building for heating in winter and for cooling in summer, and minimize the dangers to life and property damage from tropical storms. Passive cooling systems and natural or fanned air ventilation are required solutions for climate control.

2.2 Building Layout

A spread-out building with large operable windows enables better natural cross-ventilation. Once the building is cross-ventilated during the daytime hours its indoor temperature tends to follow the outdoor pattern. Shading devices which intercept direct solar radiation are less effective at minimizing the heat effect due to the level of water vapor in the air.

2.3 Building Orientation

Natural ventilation, in reference to wind direction, should be the primary factor associated with building orientation. The eastern and western walls and windows receive, year-round, much more radiation than the northern and the southern walls. Hot-humid regions at low latitudes have winds mainly from the east (the trade winds belt), changing in a given north-south shift of the trade winds belt.

2.4 Building Elevation

Hot-humid regions often experience floods. Raising the buildings on stilts reduces the likelihood that floods will reach the floor level. The land in hot-humid regions is often covered by vegetation, raising the building off the ground can improve greatly the potential of ventilation. The windows of single-story buildings at the ground level are often located in the zone of restrictive wind speed, a factor which reduces the potential for cross-ventilation of the indoor space.

2.5 Building Openings

Openings in a hot-humid climate play a major role in determining the thermal comfort of the occupants. Their location and size determine the ventilation conditions of the building. Large openings in all the walls can provide an effective cross-ventilation solution. However, solar radiation can penetrate directly though unshaded openings into the interior of the building and elevate the indoor temperature above that of the outdoor

In low-latitude regions it is possible to provide shading for walls and openings facing north and south; in multistory buildings, by wide balconies extending along the whole façade. Eastern and western walls are subjected to the impact of the low sun. Fixed shading for the windows should therefore be capable of blocking the low sun rays in order to be effective.

4. Prevailing Winds

5. Flood Zones 6. House design by Touzet Studio

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Prevailing WindsWind Frequency (Hrs)

8. Direct Solar Radioation (W/m2)7. Wall Assembly


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2.6 Building Materials

The role of materials in hot and humid regions is to minimize solar heating of the interior during daytime and to maximize the rate of cooling during the evening and night hours. Lightweight materials such as wood construction are typical in hot and humid climates. Low heat capacity can enhance the rate of cooling of the building during the evening and night hours. The need for thermal resistance in a building is determined by the desired to minimize the elevation of the indoor radiant temperature, namely the temperature of the surfaces of the roof and the external walls, above the indoor air temperature.

2.7 Urban Density Urban density is among the major factors which determine the urban ventilation conditions, as well as the urban temperature. Under given circumstances, an urban area with a high density of buildings can experience poor ventilation and strong “heat island” effect. In hot-humid regions these features would lead to a high level of thermal stress of the inhabitants. Economic and social influx dictates that cities must become more concentrated, making it necessary to increase the density to reduce the cost of public services and achieve required social cohesiveness.

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Component R ( SI) Inside air film 0.12 Gypsum board (0.375 in) 0.056 Plastic film vapor Retarder nil Glass fiber batt Insulation (6in) 3.35 Plywood (0.5in) 0.11 Wood sliding (1in) 0.14 Outside air film 0.03 Total resistance (R) 3.81 U (I P) = 1/∑ R = 1/3.81 = 0.262

9. Visualizing Density

10. Density Classification

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context context context

neighborhood plan neighborhood plan neighborhood plan

street pattern street pattern street pattern

Beverly Hills, CA 0.2 units / acre Hollister, CA 0.3 units / acre Broomfield, CO 0.3 units / acre

LESS THAN 1 UNIT PER ACRE

Urban Residential Zone Response to Hot and Humid Climate

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ARTICLE 3. Zoning Regulation

3.1 Stories

Stories are defined as the allowable amount of building levels per structure. Ground floor units can extend to a maximum height of 14 feet (4.23m) in response to commercial applications and crowd volumes. The rest of the floors have a maximum height of 10 feet (3.05m). Floors associate with mechanical systems and lifts may request variance.

3.2 Siting

Siting structures on a parcel determines the relationship with the street as well as the impact associated with the orientation of the building. In an urban residential zone all ground level units are to rest on a 2’ (0.6m) podium. The podium functions both as a first defense system for flood control and an onsite stormwater filtration system.

3.3 Lot Coverage

Lot Coverage is determined via parcel size. In an urban residential zone (T4) parcels less than 25’ (6.7m) are restricted to 45% coverage at ground level. Parcels greater than 25’ (6.7m) can cover 65% of the parcel at ground level.

3.4 Dwelling Units

Dwelling Units (DU) for an urban residential zone are determined by parcel width. Parcels less than 25’ (6.7m) have a maximum of 1(DU), parcels between 25’-69’ (7.6m-21.0m) have a maximum of 6(DU), and parcels larger than 70’ (21.34m) have a maximum of 12(DU). Also, parcels less than 25’ (6.7m) are allowed an auxiliary unit detached from the primary unit.

3.5 Setbacks

Setbacks site buildings to be consistent with intended character and functional requirements of the neighborhood. Setbacks also improve connection between varied uses and the public street. Cross- ventilation also benefits from multi-story setbacks.

3.6 Parking

In order to maximize parking slots and minimize the visual impact of parking areas and curb cuts all residential parking is to be allocated behind ground floor commercial zones and accessed by the alleyways. Parking thoroughfares are to be shared by all owners in order to offer the maximum amount of parking slots on the grown floor.


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ARTICLE 4. Sustainable Elements

4.1 Podium

Podiums are set back a minimum of 4’ (1.21m) from the lot line as a means to expand pedestrians’ right-of-way allotting space for a green belt which can house trees that will provide shade and help reduce the heat island effect. The podium functions both as a first defense system for flood control and an onsite stormwater filtration system. A layer consisting of a mixture of sand and gravel under the podium can increase the area of effective infiltration below the surface, thus increasing the rate of water absorption in the ground.

4.2 Ventilation

A major factor determining the level of thermal stress in a hot and humid region is the potential for natural ventilation. Ventilation is the amount of air circulated through a space. Ventilation ensures that enough air is supplied for the number of occupants preventing accumulation of carbon dioxide and other pollutants in the space.

4.3 Rainwater Harvesting

Rainwater harvesting is the accumulating and storing of rainwater for reuse. Rainwater collected from the roofs of buildings can make an important contribution energy use. The use and implementation of roof ponds has the potential to stabilize interior temperatures. Roof ponds sized for cooling will likely be nearly equal in area to the floors of the buildings they cool. Average pond depth is between 3 and 6 in (75 and 150 mm).

4.3 Terrace Vegetable Garden

Terrace vegetable gardens are patios or balconies designed with an assortment of containers to grow vegetable plants or seeds. Low, upright vegetables are chosen to take advantage of structures and space to provide harvesting of food throughout the summer planting season. By designating a percentage of the parcel to food production, on the residential level, terrace vegetable gardens forester commitment to sustainable urban living.

“The key to shifting the building regulatory system towards greateracceptance of more sustainable, alternative approaches is to create a contextin which those alternatives can be seen both as positive and as representing areduction of risk, rather than an increase in risk… The larger, ecologicallybased risks to public welfare must eventually be seen as risks that demandresponsibility for protecting public welfare as much as structural integrity, firesafety, or means of egress.” David Eisenberg

11. Ventilation Diagram

12. Rainwater Harvesting Systems

14. Terrace Vegetable Garden

13. Retaining Bladders

13. Roof Ponding Systems Diagram


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ARTICLE 5. Design Standards 5.1 Zoning Table

Height Type A Type B Type C Stories

Main Street Lot 3 max 3 max 3 maxSide Street Lot 3 max 3 max 2 max

Siting Type A Type B Type C Zone Lot Lot Coverge (Ground Level) 65% 45% 65%Lot Width 70’+ 26’-69’ < 25’Dwelling Units per Primary Residential Structure (min/max) 8/12 3/6 1/1 Auxiliary Dwelling Unit (min/max) 0 0 0/1 Ground Residential limited to ADA accessible Units (min/max) 0/2 0/2 0/1 Setbacks Main Street Ground Floor: 8’ min 8’ min 8’ min

50% Frontage 12’ min --- 12’ minSecond Floor: 14’ min 14’ min 14’minThird Floor: 14’ min 14’ min 14’minSetbacks Side Street Ground Floor: --- --- 8’ min

40%Frontage 14’ min 14’ min ---60%Frontage 8’ min 8’ min ---

Second Floor: --- --- 8’ min20%Frontage 8’ min 8’ min ---80%Frontage 14’ min 14’ min ---

Third Floor: --- --- ---40%Frontage 14’ min 14’ min ---60%Frontage 18’ min 18’ min ---

Setbacks Alley Ground Floor: 4’ min 4’ min 4’ minSecond Floor: 4’ min 4’ min 4’ minThird Floor: 4’ min 4’ min ---At Side Ground Floor: 0’ min 0’ min 0’ minSecond Floor: 2’ min 2’ min 2’ minThird Floor: 4’ min 4’ min ---Parking Shared surface Parking behind commercial Sustainable Elements Type A Type B Type C Building Configuration All street level structures sits on a 2’min podium 2’ min 2’ min 2’ minVentilation: Residential units, Exception ADA accessible units

10’ aboveground min

10’ above ground min

10’ aboveground min

Rainwater Storage Roof Pond Roof Pond Roof PondTerrace Vegetable Garden 10% Lot 10% Lot 10% Lot


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ARTICLE 6. Diagrams 6.1 Section Diagram

6.2 Plan Diagram

6.3 Axonometric


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References “Building and Urban Design For Hot-Humid Regions” Building and Urban Design Guidelines. Ch11.

“Green Building and LEED Core Concepts” 2009 First Ed. USGBC

Eisenberg, David and Yost, Peter. 2001. “Sustainability and Buildings Codes” Environmental Buildings News, 10(9) 1 8-15

Maclaren, W. Virginia. 1996. “Urban Sustainability Reporting” Journal of the American Planning Association

Mckeegan, Noel “Rainwater storage solutions stays out of sight”. 26 June 2007. Web. 17 Apr 2011. http://www.gizmag.com/go/7519/

Stein, Benjamin, et al. 2006. Mechanical and Electrical Equipment for Buildings. New Jersey: John Wiley & Sons, Inc.

Wackernagel, Mathis and Rees, William. 1996. “What Is and Ecological Footprint?” Our Ecological Footprint.

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Hot and Humid Climate Zoning