Expose and review 2x4 vs 2x6 exterior wall studs

[afontani]

Description

It would be good to see a column in the ResStock results that describes the wall studs and thickness. This would provide more detail on what type of envelope retrofits might be reasonable (ex: cavity insulation or exterior panels).

Information on stud size currently

In OpenStudio-HPXML assigns a 2x4 or a 2x6 wall if there is adequate space in the cavity to achieve the specified wall assembly r-value. Here are the construction sets that OpenStudio-HPXML uses for wood stud walls (wood construction sets). There are other construction sets for CMU and Steel wall types.

An attempt to figure out what ResStock currently specifies

We might want to do a review of what the outputs will look like. I tried to reproduce some of the calculations and came to this table below. It seems that the wall thickness is based on 2 ResStock inputs wall_assembly_r and exterior_finish_r.

Insulation Wall	wall_assembly_r	Geometry Wall Exterior Finish	exterior_finish_r	cavity type
Wood Stud, Uninsulated	3.4	None	0	2x6
Wood Stud, Uninsulated	3.4	Stucco, Medium/Dark	0.2	2x4
Wood Stud, Uninsulated	3.4	Vinyl, Light	0.6	2x4
Wood Stud, R-7	8.7	None	0	2x6
Wood Stud, R-7	8.7	Wood, Medium/Dark	1.4	2x6

Looking at the table above, basically only the Wood Stud, Uninsulated cavity is a little complicated. Any Wood Stud wall with R-7 or more as an option will have a 2x6 cavity type regardless of the exterior finish. For “Wood Stud, Uninsulated” options, a 2x6 will exist if the exterior finish “None” or “Stucco, Medium/Dark” because the r-value of the exterior-finish r-value is low enough to allow for a 2x6 cavity. Since other exterior finishes have a higher exterior finish r-value, the cavity must be smaller (a 2x4) to accommodate the supplied wall assembly r-value.

cc @ekpresent

[shorowit]

Related: NREL/OpenStudio-HPXML#1366