2. Design Techniques
http://www.montanagreenpower.com/faq/passive_solar_design.php#q2
Direct Gain – Solar radiation directly
penetrates and is stored in the living space
Indirect Gain – Solar radiation is collected and
stored and distributed using thermal storage
material. Trombe Wall
Isolated Gain – Solar radiation is collected in a
space that can be isolated like a sunroom.
9. Passive Solar Design
Techniques
Select, orient and size glass to optimize
winter heat gain and minimize summer heat
gain.
Size south-facing overhangs to shade
windows in summer and allow solar gain in
winter
Add thermal mass in walls for heat storage
Use natural ventilation to reduce or eliminate
cooling needs
Use daylight to provide natural light
10. U-Factor
U-FACTOR
The rate of heat loss is
indicated in terms of the
U-Factor of a window
assembly. The insulating
value is indicated by the
R-Value which is the
inverse of the U-Value.
The lower the U-Value
the greater a windows
resistance to heat flow
and the better the
insulating value.
11. Solar Heat Gain Coefficient
The SHGC is the fraction of
incident solar radiation
admitted through a window.
SHGC is expressed as a
number between 0 and 1.
The lower a windows solar
heat gain coefficient, the
less solar heat it transmits.
12. Visible Transmittance
The visible transmittance is
an optical property that
indicates the amount of
visible light transmitted.
Theoretical values vary
between 0 and 1, but most
values are between 0.3 and
0.8
13. Heat loss and gain occur
by infiltration through
cracks in the window
assembly.
Air leakage is expressed
in cubic feet of air passing
through a square foot of
window area.
.3 is recommended for
Oregon
14. High number for
cold climate. Low
number for warm
climates
The lower the
number the better
the insulating
value
The best windows
have air leakage
rating between 0.1
and 0.6 cfm/ft.
Varies from 0 to
1.0 The higher the
# the more light is
transmitted.
15.
16. Window Selection
Heating Climates
Reduce window area on north, east and west
facing walls.
South facing windows should have a high Solar
Heat Gain Coefficient (SHGC) 0.60 or greater
Low U-Factor 0.35 or less to reduce conductive
heat transfer
17. Window Selection
Cooling Climates
Use north facing windows along with shaded
south facing windows
Shading can come from landscaping, overhangs,
shutters, and solar window screens
Use windows with U-Factors below 0.4 and a
SHGC below 0.55, which will help cut cooling
costs
18. Suntempering
A strategy used in cold climates where most of
the glazing is oriented on the south side, is to
provide glazing up to 7% of the total square
footage.
Editor's Notes
The SHGC is the fraction of incident solar radiation admitted through a window. 0 to 1 Low number indicates low admittance and high number indicates high admittance of solar radiation.
