The exteriors industry is filled with jargon. It’s hard enough to understand difference between the numerous window styles or roofing and siding options, let alone all the components and other terminology that go along with each. R-values are no exception. Many people don’t even know they exist. Those that do can’t tell which materials are best for their home based on their inherent R-value. They know it has something to do with energy efficiency, but everyone just tends to ask the same question: “will this cut down on my energy bills?

What are R-Values?

An R-value is the measurement of a construction material’s ability to resist heat flow. In the simplest terms, it measures how well a material stops heat from moving through it. Why is this important? Materials with better R-values will stop heat from escaping your home in the winter and prevent it from entering your home in the summer. Choosing the best materials based on R-values make it easier for you to regulate the temperature of your home. And yes, better R-values can cut down on energy costs because your furnace or air conditioner will have to work less hard to keep the temperature at the value you have your thermostat set to. Will it save you house loads of money, no, but you can see a difference in what you pay in utilities over time.

How R-Values are Measured

For those looking for the scientific equation, an R-value’s equation looks like this:

r value equation

In this equation, Rval  is the R-value, or absolute thermal resistance,  the Delta T is the temperature difference between the warmer surface and colder surface of a barrier, and the phi q symbol is the heat flux through the barrier.

For those just looking for a better explanation, larger R-values mean materials are more resistant to heat, meaning they are better insulation. R-values can also stack, which means if you place two materials up against one another (say your siding and the wood that makes up your home) you can get their total R-value by adding the two together.

The Better Measurement

Now that you have a better understanding of R-values, we can throw one more term your way: U-Values. This is the better term to focus on when choosing the right material because it measures the overall exterior components ability to transfer thermal energy. It is commonly used in windows and doors, and is calculated by dividing the number one by the sum of the R-Values of the materials used in the window or door.

A lower U-value means that the object has better thermal resistance, which means it will be more energy efficient. When shopping for materials for your home, look for lower U-values for better energy performance!


Not sure which materials are right for your roofing, siding or windows project? Contact Schmidt Roofing today!

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