Let me explain when the general public hears an r 13 wall insulation they believe that in fact they have an r 13 insulation value in their exterior walls.
													
																	Exterior wall r value insulation chart. 
								
	
		
	
																	Insulation level are specified by r value. 
																	In the chart above you will notice that there are two vastly different r values provided for insulated metal doors with polyurethane insulation. 
																	The table below shows what levels of insulation are cost effective for different climates and. 
																	What is the difference. 
															
													
								
	
		
	
																	U factor is a measure of a component assembly in its conductive and radiate capacities. 
																	As a benchmark one inch of solid wood has an r value of 1. 
																	For example a wall with 3 fiberglass batting r value of 10 8 11 9 may have an overall r value of nearly 14 because of siding sheathing and drywall. 
																	Typical recommendations for exterior walls are r 13 to r 23 while r 30 r 38 and r 49 are common for ceilings and attic spaces. 
															
													
								
	
		
	
																	These r values are a sum meaning this should be the total r value once you add up the entire depth of insulation. 
																	Recommended home insulation r values. 
																	R value is a measure of insulation s ability to resist heat traveling through it. 
																	Also included is the hugely helpful insulation zip code calculator that spells out the suggested amount of r value necessary for the different portions of a structure like foundation interior and exterior walls attic and more. 
															
													
								
	
		
	
																	The higher the r value the better the thermal performance of the insulation. 
																	See the department of energy s doe ranges for recommended levels of insulation below. 
																	R inch r thick ness insulation materials fiberglass batt 3 14 fiberglass blown attic 2 20 1 fiberglass blown wall 3 20 rock wool batt 3 14 rock wool blown attic 3 10 rock wool blown wall 3 03 cellulose blown attic 3 13 cellulose blown wall 3 70 vermiculite 2 13 air entrained concrete 3 90 urea terpolymer foam 4 48. 
																	Additional r value for a masonry wall constructed using these materials needs to add the insulating value of additional wall components typically included such as 1 solid foam polyisocyanurate r 8 extruded polystyrene r 5 expanded polystyrene r 4 or 1 of perlite r 2 7 and for an exterior air film winter no wind r 0 17 an interior. 
															
													
								
	
		
	
																	In comparison an inch of blown fiberglass insulation has an r value of 3 1 3 4 and an inch of blown cellulose in an attic has an r value of 3 2 3 7. 
																	Based on astm c518 calculation method the door has an r value of up to 11 but using astm c1363 tested operable the same door only have an r value of up to 3 5. 
																	Along with knowing the r value of a particular insulation it is also important to calculate the r value of a total system. 
																	Depending on where you live and the part of your home you re insulating walls crawlspace attic etc you ll need a different r value.