Jm suggests that design professionals use 5 7 r inch as a design specification for its foam products.
													
																	Polyiso roof insulation r value per inch. 
									
	
		
	
																	Building science corporation bsc and others have been examining this difference. 
																	Dated its r value recommendations for polyisocyanurate insulation used in roof systems. 
																	Polyiso has a high r value per inch compared to other insulation products. 
																	Jm revised lttr values. 
															
													
									
	
		
	
																	However labeled r value differs from in service r value for many insulations. 
																	Fm approved subject to the conditions of approval as a roof insulation when installed as shown in the current edition of the factory mutual research approvals guide. 
																	Jm is proud to be a pima member and have its product third party certified under the pima quality mark program. 
																	Let s use the r value of iko s polyiso insulation enerfoil tm as an example. 
															
													
									
	
		
	
																	It has one of the highest r values per inch of thickness among common insulations. 
																	R value chart for enerfoil tm rigid foam faced insulation conditioned per atsm c1289 test method astm c518 1 2. 
																	Polyiso is unique in that the r value increases with the thickness of the foam so three inches of polyiso has a higher r value per inch than two inches. 
																	Benefits of energyguard polyiso roof insulation include. 
															
													
									
	
		
	
																	Excellent lttr value compared to any other fm class 1 rated products of equivalent thickness. 
																	Polyiso still remains the highest r value per inch of any available insulation. 
																	Membrane roof systems 2015 nrca had recommended designers use in service r values of 5 0 per inch thickness in predominant.