How to model framed constructions
Posted by Michael J. Witte, Last modified by Michael J. Witte on 28 November 2017 07:15 PM
Question: I am simulating a house that has roof rafters with no insulation in between them. I am trying to determine how to define the parameters for the rafters material layer in the roof construction, which is 23% wood rafters and 77% air. How do I best do this? I want a solid baseline design so I can go in later and replace this construction with one that has insulation in between the wood rafters.

Answer: The most common approach for modeling a framed construction is to divide each building surface into two parts, one to represent the framed area and one to represent the insulated (or in this case, uninsulated) area. Because EnergyPlus surface heat transfer is 1-dimensional, some users will set the framed area to something greater than the actual framed percentage to allow for thermal bridging.
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