C-factor Walls
These constructions will be applied only to underground wall surfaces during the building drawing process. C-factor walls differ from the usual wall constructions, in that it describes an entire construction rather than the individual layers. It is used when only the wall height (depth to the ground) and the C-factor are available. This construction type creates an equivalent layer-by-layer construction model for the underground wall in order to approximate the heat transfer through the wall. This model takes into consideration the thermal mass of the earth soil.
The only two inputs are:
C-factor – The time rate of steady-state heat flow through unit area of the construction, induced by a unit temperature difference between the body surfaces. The C-Factor unit is W/m2K. The C-factor does not include soil or air films. ASHRAE Standard 90.1 and California Title 24 specify maximum C-factors for underground walls depending on space types and climate zones.
|
Default value:
|
blank
|
|
Min & Max:
|
0 < x <= 100,000
|
|
Typical Range:
|
1 to 12 W/m2K; 0.01 to 1.0 Btu/(hr•ft2•°F)
|
|
Units:
|
W/(m2K); Btu/(hr•ft2•°F)
|
Wall height - This field is not displayed in the library. It will be auto filled when the construction is assigned to a building surface during the drawing process. It describes the height of the underground wall, i.e. the depth to the ground surface.
