The Steel Stud Condensation Potential Tool is useful in evaluating different wall configurations’ risk of concealed condensation in the steel stud wall cavity. Like all design aids, this tool also has limitations.
1) Actual condensation in the assembly
The Steel Stud Condensation Potential Tool evaluates the temperature conditions at the exterior sheathing / wall cavity interface based on a prescribed interior temperature and mean monthly exterior temperatures specific to the city chosen for evaluation. Should that interface temperature be lower than the dewpoint temperature of the interior air, then condensation can occur at that location ONLY IF interior air reaches that interface. Even if the tool predicts potential condensation risk, no actual condensation will occur if an effective air retarder in the assembly prevents outward movement of interior air (ie: exfiltration) to that interface. If outward indoor air leakage occurs then condensation will occur if predicted by the tool.
Condensation potential by the process of vapor diffusion is NOT addressed by this tool. Although a slower process, vapor diffusion can result in condensation. Condensation by diffusion is dependent on interior and exterior conditions and the insulative, vapor retarder and location of the various components of the assembly. The potential for condensation by diffusion is best addressed by the DEWPOINT PROGRAM.
2) Actual Material Properties
The Steel Stud Condensation Potential Tool uses assembly component thermal properties from manufacturers’ publications as well as reliable third-party sources to calculate thermal regimes across the wall. Should actual thermal properties differ from those used in the tool, then the condensation potential may be affected.
3) Actual Interior and Exterior Conditions
The Steel Stud Condensation Potential Tool uses published mean monthly exterior temperatues to determine the sheathing/cavity interface temperature. Should actual exterior temperatures be different than the mean (ie: warmer or colder winter) then the condensation potential may be less or worse depending on the difference in actual and mean temperatures for that particular year. Should actual interior Temperature/Relative Humidity conditions differ from those selected for analysis, the dewpoint temperature may be sufficiently affected to result in a higher or lower potential duration of condensation in the cavity.
Exterior cold air infiltration can affect the thermal regime across the wall assembly. This too may change the potential for condensation in the cavity.
Solar gain on the exterior can raise the temperature of exterior wall components, reducing the condensation potential. This effect is not evaluated in this tool.
4) Non-homogeneous assembly components
The Steel Stud Condensation Potential Tool evaluates the thermal regime across the central part of the insulated cavity, at a point furthest away from the steel stud. The thermal regime at the steel stud will be vastly different than the cavity center. The potential for condensation at the stud location is not determined by this tool. In cold climates the central portion of the wall cavity is where the exterior sheathing/cavity interface is at its coldest. This justifies evaluating condensation potential at that location only by this tool.