Environmental Controls I/IG
Lecture 8
Microclimate
Microclimate
Immediate local
conditions for
temperature,
humidity, solar
radiation, and
wind.
Microclimate
Affected by:




Earth
Wind
Fire
Water
Earth: Topography
The leeward side of a
hill can protect from
unwanted winds
Elevation
Temperature changes about -3.6 ºF
with each +1000 feet change in altitude
Salt Lake City
Park City
Elevation
Temperature
4200’
6800’
95º F
~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
Lighter surfaces
reflect radiant
heat
heat
Darker surfaces
absorb radiant
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
35ºF
10ºF
80ºF
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