b'T&R UpdateLow Rise Foam; The Good and the BadL Rene Dupuis, PhD in the 0F to 65F range.Above all else, follow the ow rise adhesive foams have become a mainstay in roof construction.While mechanical fasteningmanufacturers instructions as each low rise foam product is and will continue to be widely used, many roofsis a little different.This has to do with rise and set time utilize bead applications of low rise foam. also, as some low rise foam needs to attain an initial bond Fig.1Hard glassyoff ratio low rise foam; has littlebefore walking Contractors like the product and todays manufactures ofadhesive strength, no foam expansion. the insulation low rise foam have done a good job in providing laborboards in.You saving methods and especially equipment to expeditedo not want putting down their product. to destroy the There are basically two types of low rise foam adhesive: freshly formed 1.One Part Moisture Cure; this stems from olderbond.urethane technology and was the first one on theThe Badmarket years ago.It would slowly cure out; dry hotTwo component weather sometimes left you without any cure.Currentlow rise formulations are much better. polyurethane 2.Two Component Polyurethane; this is a rapid curefoam consists product. Large amounts of two component low riseof an A side foam are in use today.It is shipped in dual cartridge,which is the disposable containers to be used with dispensers andpolymeric pump grade components.These products are putisocyanurate.down in a cream bead form, being manually guidedThe B components are the polyolsbuilding blocks of by the mechanic.The bead is usually dispensed inresin and other components.It is critical that these come 1/2 to 3/4 wide liquid beads.The material usuallytogether in a 1:1 mix.If they do not, we can get off ratio spreads out and may rise up to an inch.Depending onfoam and then things can go bad.The foam manufacturers temperature and humidity, you have about 10 minuteshave good formulations that have some leeway in going off to work with the product. ratio.The Good If you do not catch the problem, you can unfortunately When applied during mild to warm temperature conditionsbuild a lot of bad roof in a day; the boards will really not be (60F - 90F), production is fast and the insulation beadsadhered very well or bonded at all.Your applicators need being bonded will need to be walked in.Cure time isto be checking on the quality of foam frequently.Free rapid, generally within 58 minutes.Once the boardmoisture, damp conditions or a thin layer of morning dew (use 4 x 4 boards) is stuck, it is normally well adhered. can really create a problem.Tearing off an adhered single ply roof can be a lot of work because of the tenacity of the foam adhesive even at 12Off ratio foam is going to go one way or another, spacings. Generally you want to use beads 12 on centerdepending if more A (Part 1) is present than B (Part 2) in the field of the roof and probably 6 on center at theor more B is present than the A side.corners and perimeters.Check with your roof designer orDo not apply these materials if fog, misty conditions or roof manufacturer for the specified spacing.Rememberlight precipitation is present.You will live to regret it.that the 12 spacing is nominal, there are no guidelines onTwo component foam is a great product but like every the boards.I allow for a field tolerance in spacing as weother product we use, it has its strength and weaknesses. know 12 on center is more than adequate, based on fieldBut any free moisture present when you lay down the foam experience to date.We do not know what factor of safetywill turn it into B rich material, making it go off ratio.you have in uplift, as no one has studied that issue. Excess isocyanurate or A component (Part 1) problems Store the product at 70F - 90F; if the temperature dropsare more difficult to spot; you should look for irregular into the 40F range, set times slow way down.You mayglossy cell structure, brittleness, improper rise and poor need a winter grade product, which generally are goodadhesion ability.Figures 1 and 2 demonstrate what to look 8 www.mrca.orgMidwest Roofer'