R-Values and U-Factors of Single Wythe Concrete Masonry Walls

CMHA TEK 06-02C

Single wythe concrete masonry walls are often constructed of hollow units with cores filled with insulation and/or grout. This construction method allows insulation and reinforcement to be used to increase thermal and structural performance, respectively, without increasing the wall thickness.

U-factors and R-values are used to estimate heat flow under steady state conditions (neglecting the effects of thermal mass). These steady-state values can be used in conjunction with factors such as thermal mass, climate, and building orientation to estimate a building envelope’s thermal performance, typically using software.

This TEK lists thermal resistance (R) and thermal transmittance (U) values of single wythe walls. Cavity wall R-values are listed in TEK 06-01C, R-Values of Multi-Wythe Concrete Masonry Walls (ref. 1).

The R-values/U-factors listed in this TEK were determined by calculation using the code-recognized series-parallel (also called isothermal planes) calculation method (refs. 2, 3, 4). The method accounts for the thermal bridging (energy loss) that occurs through the webs of concrete masonry units. The method is fully described in TEK 06-01C. Alternate code approved means of determining R values of concrete masonry walls include two-dimensional calculations and testing (ref. 2).

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