Article #1497 - COMcheck Web-Based Training Questions - Orientation/Projection Factors
This article contains questions asked during the August 18, 2005 live broadcast of the
COMcheck Web-Based Training
session. The original language of the questions and answers has been modified to make them as generic as possible while retaining the applicable specific information.
Why do we not input orientation of building or walls and windows?
Orientation is optional in COM check . If an orientation has been assigned to each wall, window, door, and below-grade wall assembly, the compliance calculation will be based on a proposed building using those orientations. This result may be slightly different than the result obtained when orientation is not specified. In the latter case, assemblies are assumed to be equally distributed according to default aspect ratio of 2:1. The orientation-specific compliance calculation will not be performed until all assemblies have been assigned an orientation.
How does the program account for ASHRAE 90.1 allowing for higher SC (shading coefficient) on the north windows?
If an orientation has been assigned to each wall, window, door, and below-grade wall assembly, the compliance calculation will be based on a proposed building using those orientations. This result may be slightly different than the result obtained when orientation is not specified. In the latter case, assemblies are assumed to be equally distributed according to a code-specified aspect ratio. The orientation-specific compliance calculation will not be performed until all assemblies have been assigned an orientation.
If we have two buildings facing each other with a bridge connecting them and windows under the bridge, how do we calculate the projection factor? Or if we have doors or windows in a wall of a covered breezeway, how do we calculate the projection factor?
Technically, this would be the full length of the bridge or breezeway divided by the distance from the bridge/breezeway to the bottom of window.
Are projection factors not allowed in RES check ?
Orientation and Projection Factors are not available unless the project is in a location of < 3500 heating degree days and the code is 1998 IECC, 2000 IECC, or 2003 IECC or when Pima, Arizona < 4000 ft or Georgia. The reason these options are not available outside of the locations listed is that the program offers credit only towards a mandatory solar heat gain coefficient (SHGC) of .40.
Are projection factors for windows available in RES check ? We are using awnings and louvers to reduce HVAC load and would like to take credit for that in a residential project.
Projection factors are not available unless the project is in a location of < 3500 heating degree days and the code is 1998 IECC, 2000 IECC, or 2003 IECC or when Pima, Arizona < 4000 ft or Georgia. The reason these options are not available outside of the locations listed is that the program offers credit only towards a mandatory solar heat gain coefficient (SHGC) of .40.