Editor's note: Following are the author's opinions about venting base sheets. Views expressed are not necessarily those of NRCA.
In the roofing industry, venting base sheets have received little media attention for a product group that delivers toughness combined with the need to prevent blistering. However, the application of venting base sheets over polyisocyanurate insulation has been debated within the roofing industry in recent years. Contractors have worried about the performance of polyisocyanurate insulation in such instances—concerns range from facer delamination to dimensional stability issues. In addition, because of concerns regarding blistering and the ability of foam plastic insulation to withstand foot traffic, NRCA recommends using cover boards over polyisocyanurate insulation.
Following is the history of these recommendations and arguments for using a venting base sheet over polyisocyanurate insulation.