Architects and Specifiers

Low slope roof penetrations can be a source of problems if not done correctly. Pipe, vent, and conduit penetrations through low slope roof assemblies can cause problems for an otherwise tight membrane, insulation, and deck design. With many intermediate layers in roof assemblies, such as a vapor retarder and cover board, there are opportunities for things not to be done correctly somewhere in the assembly. It gets even more complex when we consider that in order to use a vapor retarder, there might be an additional cementitious board above a steel deck.

This piece is co-written by Jennifer Keegan, AAIA. The headaches of Cold Storage facility operations extend beyond making sure the ice cream doesn't melt. Owners and Operators are regularly challenged with:

With the misinformation swirling around the topic of moisture in concrete roof decks, it can be difficult to know the right approach to take to mitigate risk. Are roof failures due to moisture in concrete primarily found in lightweight concrete decks? Do vented decks alleviate moisture in concrete by facilitating downward drying? Is 28 days the right amount of time to let a new concrete deck cure? Are admixtures and MVRA's (Moisture Vapor Reduction Additives) effective in mitigating concerns around moisture in concrete roof decks? Are vapor retarders the answer? What about vented base sheets? What adhesives and insulation and cover board facers are appropriate to use in these roof assemblies?

What are the key material properties?In a previous article the use of thermal inertia to slow down heat flux through a roof assembly was discussed. In buildings where air conditioning costs dominate and heating use is relatively low, higher thermal inertia assemblies can potentially improve energy efficiency. This is particularly the case of buildings such as offices that are only occupied during daylight hours. Thermal inertia could delay the transmission of heat into a building towards the end of the day, increasing thermal comfort and allowing facility managers to reduce cooling during the day.