Mechanically fastened roof assemblies are a popular choice over steel decks. However, since steel decks are not sealed, air from the interior of the building can infiltrate the roofing system, causing condensation-related issues.

Scientists at Oak Ridge National Laboratory and the Chalmers University of Technology recently published the results of a roof membrane experiment in a paper titled, “Condensation Risk of Mechanically Attached Roof Systems in Cold Climate Zones.”

The study evaluated the ways in which a number of variables, including membrane color, humidity levels, climate zone, and air infiltration, affect the tendency toward condensation-related moisture accumulation within a roofing system.

The results of the study emphasized the importance of solar reflectance at the roof’s surface, stating, “Comparing the maximum condensate layer thickness, dl, in Figure 6 and Figure 7 reveals that the amount of accumulated moisture is almost doubled in a cool roof construction compared to a traditional black roof. Further, a cool roof will accumulate approximately twice as much moisture below the surface membrane as a black surface.”

Maximum condensate layer thickness with normal indoor moisture supply.

Roof system performance can begin to be compromised when condensation accumulation exceeds 1mm; however, the use of a dark-colored membrane like black EPDM provides a significant safety factor against condensation issues. This added safety factor – along with potential heating cost reductions and superior resistance to UV, weathering, and hail – make black EPDM a logical choice for heating-dominated climates.

For more information about black EPDM roofing options, please contact Ron Goodman at Ron.Goodman@CarlisleSynTec.com.