Thermal Barrier on sheathing under Galvalume for Cathedral roof


I am looking for recommendations for product on a re-roof for a thermal barrier to be applied on sheathing which a direct lay of Galvalume standing seam will be applied. Currently the interior cathedral ceiling interior peak can reach 150F to 200F at the ceiling peak. Looking into Polaralum. Any suggestions for thermal barriers? Thanks


There is a product called solarhide-srw. It supposed to reflect 97% of radiant heat it encounters. One roll is 48"by 250’ at ABC supply.


I think you should be looking for a true thermal barrier, not a reflective material. You don’t have a lot of choice if you want a Class A. Basically, either 1/4" Dens Deck, 1/4" Securock or a FR Base sheet. You probably also want a waterproof underlayment on the deck and then the thermal barrier. Also, when you say sheathing you mean plywood/OSB or do you mean skip sheathing as used with shakes/shingles?


Personally hate putting metal over densdeck did it once because it was speced and was pain in the ass, never again. I would say layor of ISO with 1/2" ply on top or could look into OSB/ISO laminated panels.


Iso would be great IF it meets the UL rating for this system. For example, 1/2" HD-FR (High density, fire rated) iso works well if it meets the system rating. Often, products like this are only tested on flat roofs which does not automatically give them the same rating on sloped roofs.


If looking for true thermal break and wish to use for example 1" total of ISO, you would want to install 2 layors of 1/2" ISO staggering all horizontal and vertical seams.