Title: THERMAL BRIDGES IN WALL CONSTRUCTION - NCMA
Headings: THERMAL BRIDGES IN WALL CONSTRUCTION
THERMAL BRIDGES IN WALL CONSTRUCTION
INTRODUCTION
THERMAL BRIDGING
Causes
Effects
Requirements
SINGLE WYTHE MASONRY WALL
CONCRETE MASONRY CAVITY WALL
MASONRY VENEER WITH STEEL STUD BACKUP
SLAB EDGE & PERIMETER BEAM
MASONRY PARAPET
References

Content: According to ASHRAE Standard 90.1, acceptable methods to determine the R-value of insulated steel studs are: testing, modified zone calculation method, or using the insulation/framing layer adjustment factors shown in Table 1. The effective framing/cavity R-value shown in Table 1 is the R-value of the insulated steel stud section, accounting for thermal bridging. Using these corrected R-values allows the designer to adequately account for the increased energy use due to the thermal bridging in these wall assemblies. Table 1 shows that thermal bridging through steel studs effectively reduces the effective R-value of the insulation by 40 to 69 percent, depending on the size and spacing of the steel studs and on the R-value of the insulation. Because the steel studs are typically in contact with the interior finish, local cold spots can develop at the stud locations. In some cases, moisture condenses causing dampness along these strips. The damp areas tend to retain dirt and dust, causing darker vertical lines on the interior at the steel stud locations. If warm, moist indoor air penetrates into the wall, moisture is likely to condense on the outer flanges of the steel studs, increasing the potential for corrosion of studs and connectors and structural damage of the wall. Gypsum sheathing on the exterior of the studs can also be damaged due to moisture, particularl