WSRCA Technical Bulletin 2019-LSII-1

By WSRCA.

Condensation potential & damage related to white & light-colored roof systems.

Issues surrounding reports of condensation beneath light-colored single-ply roof membranes in some climates has been one of the more discussed industry-related topics over the past decade. Looking back, it appears that, building owners or tenants would report a mysterious “leak” or water intrusion into interior conditioned space and simply suspected that it was a leak likely associated with a weather event. As more and more of these situations were reported and then evaluated by the roofing contractor or professional roofing consultant certain patterns began to emerge in various climactic zones and general type(s) of roof assemblies.

Many of the similar roof system commonalities consist of mechanically-attached, white or light-colored single-ply roof membranes, installed over wood or steel roof decks with no vapor retarder. Of these roof systems reported as problematic, numerous lack multi-layers of insulation (with offset and staggered joints) and reportedly some have only one layer of insulation, and that is believed to have exacerbated the situation. As evaluations continued, the presence of interior-generated moisture as well as the lack of a vapor retarder and adequate ventilation was determined to be associated with condensation, forming on the underside of the roof membrane or roof deck, rather than a leak caused by some defect or puncture within the roof membrane.

WSRCA has been monitoring issues of condensation and moisture accumulation reported with mechanically-attached, white and light-colored single-ply roof systems, which were constructed without a vapor retarder, and we offer the following information to our Members. As this Bulletin will clarify not all roof systems may be appropriate for all climates.

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