Climate Analysis

Climate AnalysisClimateMost important environmental factor and the first one that should be consideredCan dictate what passive design strategies will be suitable and effective

ClimateDictated by its latitude altitude, and terrainInfluences many aspects of the buildings designIndoor tempPredicted energy loadsFactors controlling human thermal comfortClimateNot and interchangeable term with weatherClimate is the average atmospheric conditions over a long period of timeWeather is the daily temp and atmospheric conditionsClimateClassificationsKppen-Geiger climate classification systemUS climate zonesCalifornia climate zonesMicroclimateMicroclimateSmall area that features different climate characteristics from the overall climate zone it is located inTypically caused by different topographies, bodies of water, vegetation, site surroundingsTemperatureVaries throughout the day and obviously yearConsider for passive heating and cooling designTwo aspects of temperature are dry bulb temp and wet bulb tempTemp

Dry bulbTemperature of the airMoisture is not consideredCelsius, Fahrenheit, or KelvinReported and referred to as air temperatureWet BulbAir temperatureTakes into account cooling potential of evaporationMeasured 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 airWet bulbMeasured in Celsius, Fahrenheit, or Kelvin100% humidity the air is completely saturatedDry and wet bulb temps will be the sameAny other scenario the wet bulb temp is less than the dry bulb temp, due to evaporative coolingThe larger the difference between dry and wet temps, the drier the air and lower the relative humidityTempSites will obviously varyHeating will dominate design requirements for most of the year in oneCooling may dominate the design in anotherTemperatures for the site can be seen on a histogram of the tempTemperature binsTemp chartsTemps are not consistent at the same time of day or yearRobust designDesign for an uncommon circumstance as well as the averageTemp chartsShows the historical averages of monthly highest and lowest dry bulb temps

Temp ChartsExtensions show extreme temps only recorded 1% of the time

Diurnal Weather AvgShow daily cycles of temp and radiation on the siteTypically included dry and wet bulb temps, direct solar radiation, diffuse solar radiation as a daily avg for each monthDifference between dry and wet bulb gives a relative humidity indicatorDifference in night and daytime temps (diurnal swing)Diurnal Weather Avg

Degree DaysTo get a sense of heating/cooling requirements a comfortable temp range should be set (comfort zone)This can be compared to the building sites actual temp over timeWhen the sites temp is outside the zone it is measured in heating or cooling degree daysDegree daysIf weather is an average of 1 degree warmer than comfortable for 1 day, the building needs 1 degree day of coolingIf it is 10 degrees warmer for 1 day then it needs 10 degree days of coolHelpful to make comparisons between buildings more fair

Degree daysTemp past a threshold, multiplied by timeHumidityCan be just as important as tempToo much can amplify the heat and make it muggy, not enough makes it too dryWarm air can hold more moisture than the cold airPeople dont 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 airLarger the difference is between the dry/wet temps, the drier the air is and the lower the relative humidity

HumidityPeople generally consider 40-55% relative humidity to be comfortableAlso affects what passive heating/cooling strategies will be effectiveEvaporative cooling is much more effective in dry climatesControlling humidity is actively done by HVACLot of latent heat in water, and de-humidifying the air requires cooling the water (lots of energy)HumidityComparing the wet/dry bulb temps can determine humidity100% humidity the air is completely saturatedDry and wet bulb temperature will be the sameAll other scenarios the wet bulb is less than the dry bulb tempDue to evaporative coolingLarger the difference between dry/wet the drier the air and lower the relative humidity

HumidityOften displayed in psychrometric chartsLike temp it varies throughout the day/yearRobust design requires designing for a rangePsychrometric ChartsComplex and difficult to understandAllows visualization of a tremendous amount of info at onceTemp (wet & dry bulb)Humidity (relative & absolute)How comfortable the climate is and what passive/active strategies will be effectiveReading the ChartHelp determine what passive strategies to useEvaporative coolingNatural ventilationNight purge ventilationDirect solar gain plus thermal massOverlay human comfort zones on the chart to see how much passive strategies help expand the zone and how much energy you can saveOrange too hotBlue too cold

Blue too humidYellow too dry

To condition air, heat/moisture is added/removed