Insulation "R" Values

 

The most important thing to be aware of with insulation is the R value, or the insulating factor. The higher the number, the better the insulator.

Don't be too shocked if the insulation in the 15 year old home you are considering isn't near the R value of a brand new home. While there is no question you could save on heating bills by adding more insulation, sometimes it can take many, many years to recoup the costs.

Choose the Right R-Value - An R-value is a measure of insulating power or ability to resist the flow of heat. Higher R-values mean greater insulating power, which means greater household energy savings and greater cost savings. Look for R-values on insulation packaging or talk to your contractor.

R-Values for Existing Homes - The levels in the table below are total R-values. Subtract the R-value of any insulation you have now to determine the R-value to purchase. If you don't have enough space or access to install the total R-value, just add insulation where space allows. To insulate walls with closed cavities, consider filling the cavity with blown-in insulation or adding rigid insulation under new siding.

R-Values for New Homes or Additions - The R-values in the table below are for existing homes. For new homes and additions, higher R-values may be required by law, so be sure to check with a local code official. If you are building new walls, consider value-engineered framing, structural insulated panels and insulated concrete forms to get high R-values.

Use this table for help in choosing R-values that are right for your home. Find your climate, your household heating system, and the area in your home that you plan to insulate and look for the matching R-value range.

Cost-Effective Insulation R-Values for Existing Homes a
If you live in a climate that is...	and your heating system is	insulate to these levels in the...
		ceiling	wood-frame wall	floor	basement/crawl space walls d	Ducts e in Unheated/Uncooled...
						attic	basement/crawl
Mixed with moderate heating and cooling requirements (i.e., VA, WV, KY MO, NE, OK, OR, WA & ID; southern IN, KS, NM & AZ; northern LA, AR, MS, AL & GA; inland CA & western NV).	gas/oil or heat pump	R-38	R-11 to R-22c	R-13 to R-25	R-11 to R-19	R-4 to R-8	R-2 to R-8
	electric resistance	R-49	R-11 to R-28c	R-25	R-11 to R-19	R-4 to R-8	R-2 to R-8
Cold (i.e., PA, NY, New England, northern Midwest, Great Lakes area, mountainous areas (e.g., CO, WY, UT, etc.)).	gas/oil	R-38 to R-49	R-11 to R-22c	R-25;	R-11 to R-19	R-6 to R-11	R-2 to R-11
	heat pump or electric resistance	R-49	R-11 to R-28c	R-25	R-13 to R-19	R-6 to R-11	R-2 to R-11

a. Adapted from the U.S. Department of Energy 1997 Insulation Fact Sheet available at (800)-DOE-EREC and Modera et al., "Impact of Residential Duct Insulation on HVAC Energy Use and Life Cycle Cost to Consumers" ASHRAE Transactions (#96-13-4).

c. R-values may be achieved through a combination of cavity insulation and rigid board insulation and are for insulation only (not whole wall).

d. Do not insulate crawl space walls if crawl space is wet or ventilated with outdoor air.

e. Use the lower R-value for return ducts and higher R-value for supply ducts.