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Although passive solar heating is best incorporated into a house
during the initial design, the concepts of passive solar heating
can also be used when remodeling or adding to your home. Window
design, and glazing choices in particular, are critical factors
for determining the effectiveness of passive solar heating in a
home. In heating climates, large south-facing windows are used,
as these have the most exposure to the sun in all seasons.
Windows can also be located to provide solar heating in cold climates
or avoid solar heating in hot climates. In cold climates, large
south-facing windows allow significant solar energy into the house
and also provide daylighting; properly sized overhangs can prevent
overheating in the summer. In hot climates, north-facing windows
can provide daylighting without heating the house.
East- and west-facing windows generally cause excessive heat gains
in the summer and heat losses in the winter, and are usually sized
small. Although overhangs are impractical for east- and west-facing
windows, vertical shading can be used, or trees and shrubs can be
strategically located to shade the windows. Landscaping has other
benefits, including natural cooling and protection from the wind.
See the EREC fact sheet, Landscaping
for Energy Efficiency (PDF 448). Download Acrobat Reader.
Windows can now be designed for a number of purposes. Some windows
are designed to let the sun's heat in while insulating against the
cold, and are ideal for south-facing windows in cold climates. Others
are designed to reject the sun's heat while providing insulation,
and are ideal for all windows in hot climates and east- and west-facing
windows in moderate climates. See Buying
for Energy Efficiency: Windows.
Thermal mass—such as tiles, masonry, or even water-filled
walls—provides a means of storing the solar energy that enters
through the windows. Built into the floors and walls near the south-facing
windows, thermal mass will absorb solar energy during the day and
keep the house from overheating. At night, the thermal mass will
release the heat, keeping the house warm.
An alternate approach is to locate a thermal mass wall on the
south-facing side of the house, with glazing on the exterior, separated
from the wall by only a few inches. The wall absorbs heat on the
sun-facing side and releases it slowly into the living space over
the course of the day. Although the wall will block the sunlight,
daylighting can still be achieved through narrow windows located
above the thermal wall.
For thermal mass to be effective, air must circulate freely through
the house to carry the heat from the thermal mass to the places
where it is needed. Fans are sometimes used, but natural convection
will often circulate the air sufficiently. For instance, a central
staircase provides an effective means for allowing hot air to rise,
and to complete the circuit, vents between the upper and lower floors
along the exterior walls will allow cooler air to flow back to the
thermal mass. Doors must be left open for this approach to work.
For more information, see Passive
Solar Design for the Home (PDF 216 KB). Download Acrobat Reader.
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