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Insulate Your House: Understanding R-Value

Oct 28, 2022 | Blog, Insulation

Walk into any big box store and you will find insulation products galore. On each package, you’ll see an R-value. But what is R-value and how do you know what number you need?

What is R-Value?

R-value refers to thermal resistance. It refers to how well the insulating material prevents heat from escaping. Thus, the higher the R-value, the greater the insulating power.

If your insulation has a high R-value, it will have a greater insulating effect. This means a warmer house in winter and a cooler house in summer. It also means lower heating/cooling bills. Energy savings!

To figure out the recommended R-value for Central Indiana, check out the chart below.

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Which areas of your house need insulation?

Just like when you put on a hat because it’s cold outside, your house also benefits from insulation in your attic. Heat rises, so having insulation in your attic will stop the heat from escaping as quickly. This insulation will get you the biggest bang for your buck, so start here.

In addition to your hat, a coat keeps you warm in the winter. The sides of your house should also have layers of insulation to trap heat as well. But, as we said before, heat rises, so the attic insulation will be more effective than the wall insulation.

Finally, you’ll want your gloves and boots. These are similar to your windows and door openings. Think of them like accessories. If your windows have a high R-value, it’s definitely going to help, but it won’t be nearly as effective as insulating the majority of your walls and attic. 

Your floor and basement are also important for thermal conductivity, so don’t forget about them, but this article is mainly concerned with above-ground insulation.

How much insulation do I need in Central Indiana?

According to the International Energy Conservation Code, Central and Northern Indiana (Zone 5) houses should have the R-values described below in the chart. Interestingly, the Indiana Building Code requires less than the recommended level, so keep that in mind. Note: For Windows, U-Value was converted to R-value for ease of reference.


House Area Recommended R-Value Indiana Code
Walls/Siding R-20 R-20
Roof/Attic R-49 R-38
Windows R-3.125 R-2.86

Do typical exteriors products have high R-value?

The quick answer is no. Most traditional siding products have R-values below 1. Most roofing products are equally minimal.


Common Siding R-Values

Wood Shingles 0.87
Vinyl Siding 0.61
Brick Siding 0.40
Stucco 0.40


Common Roofing R-Values

Asphalt Shingles 0.44
Metal Roofing Panels No Useful R-Value
Slate Roofing 0.05
Wood Shakes (Cedar) 0.94

To summarize, the most important area to focus on when trying to increase the energy efficiency of your home is the attic space. The greater the R-value, the better the insulation. To find out more about insulating your home, talk to a Rojas Roofing specialist today!