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Houses & Passive Solar
Cooling
Though some of the passive solar cooling principles and
techniques are common to passive solar heating, there are also
some specific passive solar techniques for cooling, specially
valid in hot and temperate climates. They include, namely, the
right thermal mass for
cooling, ventilation and
shading…
Shading strategies & Trees
Shading is crucial in any passive cooling strategy. The more
shaded a building is - especially the windows and the roof - the
better.
The best shading is accomplished outside the building, and trees
(deciduous trees in most cases) are usually the best option. See
for more details: Shading
and trees
The use of trees depends a lot on the particularities of each
climate. In cold or temperate climates, do not use evergreen
trees too close to the house. Instead, use deciduous trees on
west and east side of home to reduce summer heat; and in some
cases, use deciduous trees in the sunnier side of the house
(south in the northern hemisphere; north in the southern
hemisphere).
Other Shading Strategies
Other alternatives on shading include:
- other buildings or parts of the house: one part of the
building may shade another part …
- overhangs, arbors,
screens, awnings...
- interior shading (of windows) through blinds, drapes and other
interior shading devices (Note: interior shading isn’t as
effective as exterior shading).
Shading & overhangs
Overhangs are very effective solar passive tools in many
climates: properly dimensioned they block the sun during the
summer months, when it is higher in the sky.
See, for details: Shading & Overhangs
Thermal mass and cooling
Materials
used in walls, floor and other sun-exposed parts of the house
should have adequate thermal storage or reflectance, that is,
thermal properties able to respond to the needs of the climate
where the building is located.
In cold climates the capacity of quickly absorbing solar heat
and the capacity of providing a slow release of stored heat
during the night, is crucial when choosing materials - masonry
and stone for floors, walls, and roofs are materials that have
those properties.
Obviously, thermal properties demanded to materials in hot
climates - where cooling needs are predominant - are very
different from those demanded in colt climates.
Low thermal mass materials
Low thermal mass walls and structures are a very common option
in the hot and humid climates with high nighttime temperatures.
Materials like light metal, metal roof, wood frames are very
common in passive cooling, since they don’t heat well and cool
very quickly when the sun disappears.
Reflective exterior surfaces
The use of highly reflective exterior surfaces is very
advantageous in hot climates, due to the large amount of the
sun's heat that can be reflected away by reflection. Reflective
roofing is particularly effective.
Color and texture are very important in this case. White or
close-to-white colors are good options for reflectance. Shinier
and smoother materials are also good options, since they are
more reflective, which makes the house cooler.
High mass materials
The use of high mass materials - materials that hold heat well
and cool slowly, like masonry and stone for roofs, floors or
walls - are adequate in hot dry climates, with cold or
relatively cold nighttime temperatures.
Recent studies also show that high thermal mass elements can be
used with advantage either in temperate climates and some hot
climates. Low thermal mass materials aren’t the only solution.
Natural ventilation
In hot and humid tropical climates, with small day/night
temperature amplitude, natural ventilation isn’t a good option.
But in most other cases natural ventilation is an excellent
solar house passive technique.
Obviously it demands a correct location of the windows, and a
proper orientation of the building (which in some cases may
collide with solar heating or cooling strategies).
Window style (double-hung and casement windows), window
placement and the home shape and orientation are crucial for
natural ventilation.
See, for details: Natural and
mechanical ventilation
National Renewable Energy Laboratory
www.nrel.gov
See also:
Basics on
solar systems
Orientation and shape of the house
Natural ventilation
Energy efficient
windows, doors and skylights
Solar protection
Awnings and screens
Pergolas and House Shading
House Shading, Trees and
Shrubs
Shading and climate zones
Windbreaks for your
house
Where to plant trees and
shrubs
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