Environmental Controls I/IG Lecture 8 Microclimate

Microclimate Immediate local conditions for temperature, humidity, solar radiation, and wind. Mesa Verde: vernacular, passive solar, sun angles, thermal mass

Microclimate Affected by: Earth Wind Fire Water Mesa Verde: vernacular, passive solar, sun angles, thermal mass

Earth: Topography The leeward side of a hill can protect from unwanted winds

Elevation Salt Lake City 4200’ 95º F Park City 6800’ ~86º F Temperature changes about -3.6 ºF with each +1000 feet change in altitude Elevation Temperature Salt Lake City 4200’ 95º F Park City 6800’ ~86º F

Rain & Snow Shadows Form when moisture precipitates out as air moves up slopes L: p.73 Fig. 5.2d

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, 2002 http://www.greenroofs.com/projects/pview.php?id=562

Ground Cover Impermeable surfaces reduce evaporative cooling opportunities

Surface Color Darker surfaces absorb radiant heat Lighter surfaces reflect radiant heat Darker surfaces absorb radiant heat

Urban heat island Large concentrations of thermal masses with darker and/or impermeable surfaces create urban heat islands

Wind: Topography Warm air rises Cool air drops Morning and afternoon “diurnal winds” are intensified in canyons and on sloped surfaces and diverted by hills and ridges

Convective Air Flow Warm air rises Cool air drops Recognizing air channels can help reduce discomfort or enhance comfort

Wind Direction & Speed Confirm mean (average) speed direction Consult a wind rose for prevailing direction L: p. 89 Region 1

Wind Roses January L: p.81 Fig. 5.6d

Wind Roses July L: p.83 Fig. 5.6f

Sea Breeze Effect Onshore winds occur when water temperature is lower than adjoining air temperature over land. Offshore winds are the reverse process.

Bernouli Effect Air flow closer to the ground is slowed by frictional effects of surfaces L: p.270 Fig. 10.5j

Venturi Effect Air follows the path of least resistance Wind speeds increase as cross sectional area decreases L: p.318 Fig. 11.8c

Wind Breaks/Channeling Terrain and vegetation can block or channel wind Plan Views

Solar (Fire): Mean Daily Radiation Confirm how much solar radiation is a available S: p. 1504, T. C.3

Mean Percentage of Possible Sunshine L: p. 89 Region 1 Confirm how frequently the sun shines

Solar Orientation South facing slopes get significantly more solar radiation than north facing slopes N

Water: Thermal Mass Large bodies of water moderate local temperatures A thermal mass that can act as at thermal buffer/ heat sink

Lakes & Oceans Warm temperatures are reduced in summer Cool temperatures are raised in winter 72ºF 80ºF 35ºF 30ºF 10ºF

Groundwater Groundwater table affects temperature and humidity

Rivers & Streams Moving water generates air movement

Perspiration Occurs as body core temperature rises In low RH conditions evaporation occurs and cools skin In high RH conditions evaporation is inhibited

Insolation Humidity and cloud cover affect the amount of solar radiation entering or leaving the local environment

Evapotranspiration Trees and shrubbery give off moisture that increases local humidity