b'T&R UpdateRoof Designs Where You Should Switch from Standard Reinforced Paper Facer on Polyisocyanurate Insulation to Glass Fiber Mat FacerRene Dupuis, PhD PES ince 2011, the MRCA Technical andpolyiso board suffers dimensional instability due Research Committee has been studying ato moisture trapped under the membrane.All the number of critical issues involving moisturemoisture comes up in vapor form from the concrete accumulation in roof systems constructed over newdeck, condenses up in the roof system and builds concrete roof deck. The T & R Committee alongup in the absorbent paper facers.Basically we have with the NRCA Technical Operations Committee hasheavy water vapor transport occurring especially also done an extensive research study of water basedwith structural lightweight concrete.After bonding adhesives.That work started in Januaryobserving roof failures over new concrete for the 2013 and completed in December 2014. last four years, we see one common denominator, There has been one common denominator in thisthe failure of the reinforced paper facer.The MRCA research and that is polyisocyanurate roof insulationis recommending that contractors use coated glass with standard glass fiber reinforced paper facer.Thefacers Type II, Class 2 on the polyisocyanurate official designation of this product is ASTM C1289- insulation boards.This coated glass facer does not 14 standard specifications for Faced Rigid Cellularsuffer a loss of tensile strength like the current paper Polyisocyanurate Insulation Board.The most widely used polyiso roof insulation product is Type II, Class 1 (meaning reinforced paper facers).The grade designation follows next: Grade 1 is 15 psi, Grade 2 is 20 psi and Grade 3 is 25 psi. An ASTM C1289 polyisocyanurate foam insulation board using coated glass facers is referred to as a Type II, Class 2 product.1.Roof Systems Constructed Over New Concrete DecksToday many of the new concrete decks contain structural lightweight (90-120 lb/ft3) concrete, which saves about 1/3 of the dead weight with no loss in structural capacity.However all lightweight,Figure 1. Moisture build up from concrete deck resulted in delamination of void laden aggregate are water soaked prior topaper facer on polyiso boardbatching.This ultimately yields a poured concretefacer does.From a review of most of the reinforced deck with 520% water content after cure.Evenpaper facer sold today we can conclude that it is standard weight (150 lb/ft3) new concrete decksmostly recycled paper with a small percentage fiber are causing some of our roof systems to becomenot a good product to use in a potential moist vapor detached.Current roof designs typically use low riseenvironment.foam and paper faced polyiso board construction followed by an adhered single ply or modifiedTo demonstrate the moisture gain issue new roofs bitumen membrane with cover board.Theseexperience over structural lightweight concrete systems are failing due to moisture gain withindeck construction, Figure 1 shows what was a new the roof assembly.The primary mode of failurefully adhered 060 white TPO bonded with low VOC is cohesive failure within the paper facer on theadhesive to paper faced polyiso insulation.The loss polyiso board.The beads of low rise foam are stillof membrane attachment occurred within the paper clinging onto the outer skin of the paper facer. facer as shown.Wet paper facers lose their tensile strength and2.Designs Using Water Based Bonding Adhesivescome apart, either from wind over the roof or theAir Quality Control Districts are forcing the 16 www.mrca.orgMidwest Roofer'