ARCH 2006 Climate42°C (107°F) Likely death

41°C (105.8°F) Sweating stops. Coma sets in. May damage the brain.

40°C (104°F) Heat stroke

Hyperthermia (inevitable body heating) occurs.

Evaporative cooling - sweat. (for short periods at the rate of upto 4 litres/hr)

Vasodilation (skin surface dilates). Increase in heat transportation to the surface. Rise in skin temperature and dissipation of radiant and convective heat.

37°C (98.6°F) Normal, healthy condition

Vasoconstriction. Lower skin-temperature, goose-pimples (erection of hairs)

Shivering (increase in muscular metabolism)

35°C (95°F) Hypothermia (inevitable lowering of deep-body temperature)

25°C (77°F) Likely death

Climate and Site andHuman Comfort

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ARCH 2006 Climate

Six Major Factors Determine Thermal Comfort

Environmental1. Air temperature (dry bulb temperature or DBT)2. Humidity (relative humidity RH)3. Air movement (velocity v in m/s)4. Radiation (Mean radiant temperature MRT)

Individual5. Activity6. Clothing

Thermal Comfort

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ARCH 2006 ClimateTypical Metabolic Heat Generation for Various Activities

Activity Btu/(h.ft²)RestingSleepingSeated, quiet

1318

Walking (on level surface)2.9 ft/s (2 mph)4.4 ft/s (3 mph)5.9 ft/s (4 mph)

374870

Office ActivitesWritingTypingFiling, standingWalking aboutLifting/ packing

18 20 263139

DrivingCar 18-37Miscellaneous ActivitiesCookingHousecleaningPick and Shovel work

29-3737-4474-88

Leisure ActivitiesDancing, socialCalisthenics/ exerciseTennis, singlesBasketball

44-8155-7466-74

90-140

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ARCH 2006 Climate

Bioclimatic TermsSaturation humidity line  Absolute humidity (AH) is the vapor content of air, given in grams of water vapor per kg of air, i.e. g/kg. Air at a given temperature and pressure can support only a certain amount of moisture and no more. This is referred to as the saturation humidity(SH). If this is plotted on a graph against the dry bulb (air) temperature (DBT), we get what is called the saturation humidity line.

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ARCH 2006 Climate

Relative humidity line Relative humidity (RH) is an expression of the moisture content of a given atmosphere as a percentage of the saturation humidity at the same temperature: RH = 100 x AH/SH (%)

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ARCH 2006 Climate

Wet bulb temperature lines: Wet bulb temperature (WBT) is measured by a hygrometer (or psychrometer). This consists of two thermometers, one measuring the DBT, the other having its bulb enclosed in a wet wick. 'Web bulb depression' is noted as the difference in the temperatures between the wet wick thermometer and the DBT. The difference happens as the wet wick thermometer is cooled down by the evaporation on the wick. The amount of evaporation is a direct indication of the moisture carrying capacity of the atmospheric air at that temperature and that lowers the WBT.When the air is saturated, there is no evaporation, thus the DBT and WBT readings are identical, the depression is zero. In this way, the 'status point' is determined at the intersection of the vertical DBT line and the sloping WBT line of the psychrometric chart.

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ARCH 2006 Climate

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"THE COMFORT ZONE"The Bioclimatic Comfort Chart - Victor Olgyay Design With Climate 1963

Bioclimatic Chart

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Bioclimatic Chart For Dallas, TX

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Siting of trees relative to a house is critical to ensure that during summer sun is blocked by vegetation while during the winter sun can still penetrate into the building. (After Borer and Harris, 1998).

ARCH 2006 Climate

Light Transmission Reduction by Trees

ARCH 2006 ClimateRecommended Form and Orientation for Cool Regions

Minimize the surface area of buildings (compact form) to reduce exposure to low temperatures.

Strategies• Maximize absorption of solar radiation• Reduce radiant, conductive, and evaporative heat loss• Provide wind protection

ARCH 2006 ClimateRecommended Form and Orientation for Temperate Regions

Building Form Elongated along east-west axis to maximize south facing walls

Strategies• Minimize east and west exposures which are generally warmer in summer and cooler in winter than southern exposures•Balance Solar heat gain with shade protection on a seasonal basis• Encourage air movement in hot weather, protect against wind in cold weather

ARCH 2006 ClimateRecommended Form and Orientation for Hot-Arid Regions

Building Forms should enclose courtyard spaces

Strategies• Reduce solar and conductive heat gain• Promote cooling by evaporation using water features• Provide solar shading for windows and outdoor spaces

ARCH 2006 ClimateRecommended Form and Orientation for Hot-Humid Regions

Building Form Elongated along east-west Axis to minimize east and west exposures

Strategies• Reduce Solar Heat Gain• Utilize Wind to Promote Cooling by Evaporation• Provide Solar Shading for Windows and Outdoor Spaces

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Vegetation and Temperature /Humidity changes

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Air Movement

Air movement is affected by global and local factors.Seasonal air pressureEarth’s rotationVariations in heating and cooling of the landTopography

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mda.state.mn.us

Shelter belt/Windbreak

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Windbreak Effects on Airflow

Berm Deflecting Airflow

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Shelter belts of trees should be planted at a distance of 1 to 3 x house height from the building to maximize wind drag. In addition fences in front of the building can assist this further (After Borer and Harris 1998)

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ARCH 2006 ClimateMicroclimate Analysis

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