Wood Stud Depth and Wall R-Value Calculations

Wood stud walls in ResStock are characterized by nominal wall cavity R-values. These values get combined with layers like exterior finish, OSB sheathing, the stud and cavity layer, and drywall (which add to the overall assembly R-value) in parallel path calculations that account for heat transfer through both cavities and studs (which typically reduces to overall assembly R-value). The assembly R-values are used to determine a detailed wall construction set1 that incorporates stud depth (2x4 or 2x6), framing factor, and other thermal properties such that the calculated R-value of the whole wall assembly matches the ResStock assembly R-value. See this file which shows the mapping between option names and assembly R-value.

When an insulation level is chosen, either in the baseline model or in an upgrade model, EnergyPlus calculates the heat transfer of the stud and wall cavity using multiple one-dimensional heat transfer paths. Two-dimensional heat calculations are used for foundation walls and slabs in contact with the ground.

  1. For more information how ResStock plans to address wall construction, see this GitHub issue: https://github.com/NREL/OpenStudio-HPXML/issues/1182 ↩