Wall Assembly Thermal Gradient

Testing A Designed Wall Assembly

Thermal Gradient: Shows variance in temperature through a cross section of a construction assembly.

Dew Point Analysis: A thermal gradient line is drawn/developed from outside to inside based on the R-Values of the individual building materials for a specific design condition on the outside and inside. This analysis will allow the designer to find the point in the wall where the interior design temperature will meet its dew point.

• The goal is to verify where the dew point would occur, if at all, within the wall cavity.
• Generally speaking, this is only done for heating (during winter) time design conditions

For this analysis, the entire wall assembly is ‘simplified’. Things like brackets, connectors, hangers, etc. are removed and a ‘typical’ wall section is used. The performance would be different in spots including these components, especially if they are not thermally broken.

Design Guidelines

Codes and energy guidelines like ASHRAE will stipulate design temperature ranges, along with the site weather conditions. While these are recommendations, a project's specifications will establish performance requirements that assemblies and products need to meet, especially if custom fabricated. In those cases, calculations and engineering should be submitted verifying the assembly meets the design criteria.

• Winter: ASHRAE recommends a design temperature of 68–74°F
• Summer: ASHRAE recommends a design temperature of 72–80°F
• ASHRAE recommends a relative humidity (RH) of 30–60% for indoor spaces