One important component of building construction or renovation is making the building as energy efficient as possible. This can sometimes cost a little more upfront, but it can save money over the long term, in reduced energy bills.

One of the important factors you need to consider (and be able to explain to customers) is the R-value of products used in the building and how well they trap heat in cool weather and keep heat out in the warmer months. Here’s a 101-level refresher on R-value and how it applies in construction.

What is R-Value?

The R-value tells you how well the product resists the transfer of heat. It is most often seen on insulation, but windows and doors also have an R-value. The higher the R-value, the better the product stops the transfer of heat.

R-Value of Insulation

The thickness alone of insulation is won’t tell you how warm it will keep a house as well as the R-value will. The R-value of insulation varies depending on the type. You can find a chart here showing the comparative R-value of different types of insulation per inch. The floor, walls, and attic have different requirements depending on the climate, but this map from the Department of Energy gives recommendations for how much R-value you should try to install, depending on where in the country the building is located.

That said, how well the insulation is installed can also change the R-value. For example, fiberglass insulation, whether loose or in batting form, is light and airy when sitting in a wall, but it’s not just the fiberglass itself that keeps heat in. Insulation is so light and airy because the air pockets help stop the transfer of heat. If you compress the fiberglass insulation, you reduce the amount of air trapped in the insulation and the R-value goes down as a result. When you’re buying insulation, you need to pay attention to the requirements for installation and make sure you buy a product you can install correctly in the space you have. Otherwise, you may be spending more money for a greater R-value but wasting the money by incorrect installation.

Windows

Windows are notoriously bad at allowing heat to flow in and out of the house. However, newer types of windows are far superior in terms of R-value. Single-paned windows with clear glass may have an R-value of about R-1. A double-paned window of the same thickness can have a value close to R-10. These new windows can get very pricey, but hopefully as they become more popular, the cost will come down considerably, making them more accessible for the average homeowner.

Doors

Doors can easily let heat in and out of a home, even when they’re closed. Newer styles of doors are better at trapping heat, although weatherstripping is a good way to reduce air leaks without replacing the door. A wood door will average an R-value of R-2, while a new steel and fiberglass-clad entry door can have an R-value of R-5 to R-6. It’s best to go for the most energy-efficient door the customer can afford since doors are such bad culprits at wasting energy.

There are many factors to take into account when figuring out how to make a home more energy-efficient. With a proper understanding of R-value, you can make homes more comfortable and help customers reduce their energy bills.

We’d love to hear from you! What else do you recommend that customers do to make their homes more efficient at heating and cooling?