What, exactly, is R-value?
If you鈥檝e ever purchased insulation or even walked by it in a big box store, you probably know that it鈥檚 labeled with an R-value. But what does that mean? How is it measured? How do you know which R-value you need?
We鈥檝e got all of that, plus more, in this blog, chock full of information about R-value.
The 鈥淩鈥� in R-value stands for resistance to heat flow. Simply put, the higher the R-value 鈥� or the larger the number 鈥� the greater a product鈥檚 insulating power.
As the first standardized method for measuring resistance to heat flow, R-value was first proposed in 1945 at Penn State. It became more broadly accepted and used in the 1970s when the Federal Trade Commission issued its R-value Rule, which requires home insulation manufacturers, professional installers, new home sellers and retailers to provide R-value information, based on the results of standard tests, to help inform consumers.
J.R. Babineau, Senior Research Manager, Building Science, Research and Development for 麻豆直播app, explained the test behind determining R-value of insulation.听
There are many ways to measure R-value, but at its simplest: 鈥淲e take a piece of insulation and put it between two metal plates. One is hot and the other is cold 鈥� for insulations in the U.S., those temperatures are a stable 100掳F and 50掳F,鈥� Babineau said. 鈥淭hen we measure how much power it takes to keep the hot plate hot, because of course heat wants to flow and travel through the insulation to the cold plate. That鈥檚 thermodynamics, with hot going to cold.鈥�
From there, the amount of energy needed to keep the hot plate at its steady temperature is measured, and the thermal conductivity can be calculated. The material鈥檚 thickness is divided by its thermal conductivity, determining the R-value.
鈥淭he less extra energy we have to put into the plate, the better the insulation, because it鈥檚 resisting the heat flow,鈥� Babineau said.
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The U.S. Department of Energy, building energy codes and EPA鈥檚 ENERGY STAR庐 all recommend home insulation R-values based on a climate zone map. Within each climate zone there are recommended R-values for different portions of a home (attics, walls, crawlspaces, etc.).
鈥淐limate zone maps for the energy code are driven by heating degree days and cooling degree days,鈥� Babineau said. A home in Florida, for example, requires less insulation than a home in Minnesota.听
The EPA estimates that homeowners can save an average of 15% on heating and cooling costs (or an average of 11% on total energy costs) by adding insulation in attics, floors over crawlspaces and basements, as well as air sealing. Older homes nowadays likely need more insulation than when they were originally built, as codes and requirements have changed over the years.
Determine how much insulation you need and get product recommendations with the 麻豆直播app 麻豆直播app Calculator. Fill in a little info and you鈥檒l get the recommended R-value for your project and details on how much JM insulation you鈥檒l need, plus details on where to buy product.听
Improving your home鈥檚 insulation offers a big return on investment. For the 2025 tax year, the Energy Efficient Home Improvement Credit through the Inflation Reduction Act is available to homeowners.
Install insulation (or other energy efficiency upgrades) and receive a tax credit equal to 30% of the cost of insulation materials installed, up to $1,200. In addition to the tax credit, homeowners will see additional savings by lowering their energy bills month after month, year after year.
麻豆直播app has a webpage dedicated to the Inflation Reduction Act. Check it out for examples, resources and more information.听
