Climate Most important environmental factor and the first one that should be considered Can dictate what passive design strategies will be suitable and effective

Climate Dictated by its latitude altitude, and terrain Influences many aspects of the buildings design Indoor temp Predicted energy loads Factors controlling human thermal comfort

Climate Not and interchangeable term with weather Climate is the average atmospheric conditions over a long period of time Weather is the daily temp and atmospheric conditions

Climate Classifications Köppen-Geiger climate classification system US climate zones California climate zones

Microclimate Small area that features different climate characteristics from the overall climate zone it is located in Typically caused by different topographies, bodies of water, vegetation, site surroundings

Temperature Varies throughout the day and obviously year Consider for passive heating and cooling design Two aspects of temperature are dry bulb temp and wet bulb temp

Temp

Dry bulb Temperature of the air Moisture is not considered Celsius, Fahrenheit, or Kelvin Reported and referred to as air temperature

Wet Bulb Air temperature Takes into account cooling potential of evaporation Measured by exposing a moistened thermometer bulb to air flow (wrap a thermometer in a wet cloth and swing it in the air) Evaporation of the moisture depends on the humidity of the air

Wet bulb Measured in Celsius, Fahrenheit, or Kelvin 100% humidity the air is completely saturated Dry and wet bulb temps will be the same Any other scenario the wet bulb temp is less than the dry bulb temp, due to evaporative cooling The larger the difference between dry and wet temps, the drier the air and lower the relative humidity

Temp Sites will obviously vary Heating will dominate design requirements for most of the year in one Cooling may dominate the design in another Temperatures for the site can be seen on a histogram of the temp Temperature bins

Temp charts Temps are not consistent at the same time of day or year Robust design Design for an uncommon circumstance as well as the average

Temp charts Shows the historical averages of monthly highest and lowest dry bulb temps

Temp Charts Extensions show extreme temps only recorded 1% of the time

Diurnal Weather Avg Show daily cycles of temp and radiation on the site Typically included dry and wet bulb temps, direct solar radiation, diffuse solar radiation as a daily avg for each month Difference between dry and wet bulb gives a relative humidity indicator Difference in night and daytime temps (diurnal swing)

Diurnal Weather Avg

Degree Days To get a sense of heating/cooling requirements a comfortable temp range should be set (comfort zone) This can be compared to the building site’s actual temp over time When the site’s temp is outside the zone it is measured in heating or cooling “degree days”“degree days”

Degree days If weather is an average of 1 degree warmer than comfortable for 1 day, the building needs 1 “degree day” of cooling If it is 10 degrees warmer for 1 day then it needs 10 degree days of cool Helpful to make comparisons between buildings more fair

Degree days Temp past a threshold, multiplied by time

Humidity Can be just as important as temp Too much can amplify the heat and make it muggy, not enough makes it too dry Warm air can hold more moisture than the cold air People don’t perceive the absolute number water molecules in the air(absolute humidity, measured in density) Perceive relative humidity which is represented as percentage of water vapor in the air

Larger the difference is between the dry/wet temps, the drier the air is and the lower the relative humidity

Humidity People generally consider 40-55% relative humidity to be comfortable Also affects what passive heating/cooling strategies will be effective Evaporative cooling is much more effective in dry climates Controlling humidity is actively done by HVAC Lot of latent heat in water, and de-humidifying the air requires cooling the water (lots of energy)

Humidity Comparing the wet/dry bulb temps can determine humidity 100% humidity the air is completely saturated Dry and wet bulb temperature will be the same All other scenarios the wet bulb is less than the dry bulb temp Due to evaporative cooling Larger the difference between dry/wet the drier the air and lower the relative humidity

Humidity Often displayed in psychrometric chartspsychrometric charts Like temp it varies throughout the day/year Robust design requires designing for a range

Psychrometric Charts Complex and difficult to understand Allows visualization of a tremendous amount of info at once Temp (wet & dry bulb) Humidity (relative & absolute) How comfortable the climate is and what passive/active strategies will be effective

Reading the Chart Help determine what passive strategies to use Evaporative cooling Natural ventilation Night purge ventilation Direct solar gain plus thermal mass Overlay human comfort zones on the chart to see how much passive strategies help expand the zone and how much energy you can save

Orange too hot Blue too cold

Blue too humid Yellow too dry

To condition air, heat/moisture is added/removed