Environmental Controls I/IGEnvironmental Controls I/IG
Lecture 8Microclimate
MicroclimateMicroclimateImmediate local conditions for temperature, humidity, solar radiation, and wind.
MicroclimateMicroclimateAffected by: Earth Wind Fire Water
Earth: TopographyEarth: TopographyThe leeward side of a hill can protect from unwanted winds
ElevationElevationTemperature changes about -3.6 ºF with each +1000 feet change in altitude
ElevationTemperatureSalt Lake City 4200’ 95º FPark City 6800’ ~86º F
Rain & Snow ShadowsRain & Snow ShadowsForm when moisture precipitates out as air moves up slopes
L: p.73 Fig. 5.2d
Ground Cover – Vegetation Ground Cover – Vegetation Trees, shrubbery, and grasses provide shade that prevents moisture from evaporating
Permeable surfaces reduce temperatures through evaporative cooling
Reeves House, Lopez Island, WA
Cutler-Anderson, 2002http://www.greenroofs.com/projects/pview.php?id=562
Ground CoverGround CoverImpermeable surfaces reduce evaporative cooling opportunities
Surface ColorSurface ColorLighter surfaces reflect radiant heat
Darker surfaces absorb radiant heat
Urban heat islandUrban heat islandLarge concentrations of thermal masses with darker and/or impermeable surfaces create urban heat islands
Wind: TopographyWind: TopographyWarm air risesCool air drops
Morning and afternoon “diurnal winds” are intensified in canyons and on sloped surfaces and diverted by hills and ridges
Convective Air FlowConvective Air FlowWarm air risesCool air drops
Recognizing air channels can help reduce discomfort or enhance
comfort
Wind Direction & SpeedWind Direction & Speed Confirm mean (average)
speed direction Consult a wind rose for
prevailing direction
L: p. 89 Region 1
Wind RosesWind RosesJanuary
L: p.81 Fig. 5.6d
Wind RosesWind RosesJuly
L: p.83 Fig. 5.6f
Sea Breeze EffectSea Breeze EffectOnshore winds occur when water temperature is lower than adjoining air temperature over land.Offshore winds are the reverse process.
Bernouli EffectBernouli EffectAir flow closer to the ground is slowed by frictional effects of surfaces
L: p.270 Fig. 10.5j
Venturi EffectVenturi EffectAir follows the path of least resistance
Wind speeds increase as cross sectional area decreases
L: p.318 Fig. 11.8c
Wind Breaks/ChannelingWind Breaks/ChannelingTerrain and vegetation can block or channel wind
Plan Views
Solar (Fire): Mean Daily Solar (Fire): Mean Daily RadiationRadiation
Confirm how much solar radiation is a available
S: p. 1504, T. C.3
Mean Percentage of Possible Mean Percentage of Possible SunshineSunshine
Confirm how frequently the sun shines
L: p. 89 Region 1
Solar OrientationSolar OrientationSouth facing slopes get significantly more solar radiation than north facing slopes
N
Water: Thermal MassWater: Thermal MassLarge bodies of water moderate local temperatures
A thermal mass that can act as at thermal buffer/ heat sink
Lakes & OceansLakes & OceansWarm temperatures are reduced in summer
Cool temperatures are raised in winter
10ºF 10ºF
72ºF 80ºF
35ºF 30ºF
Groundwater Groundwater
Groundwater table affects temperature and humidity
Rivers & StreamsRivers & StreamsMoving water generates air movement
PerspirationPerspirationOccurs as body core temperature rises
In low RH conditions evaporation occurs and cools skin
In high RH conditions evaporation is inhibited
InsolationHumidity and cloud cover affect the amount of solar radiation entering or leaving the local environment
EvapotranspirationTrees and shrubbery give off moisture that increases local humidity
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