October 9, 2015

5 Questions Answered About a Garage Door’s “R-value”

If you have ever shopped for a new garage door, you have probably come across an “R-value”. For example, the door’s description may read 16 ft x 7 ft, R-value 6.5.

Shoppers may get the impression that this number is important (and it is), but most are unsure about what it is, or why they should even pay attention to it when choosing a garage door. Here are the answers to some of the most common R-value questions.


What is an R-value?

R-value is simply a measurement of the resistance to heat flow. If one side of a door is cold and the other warm, the warm air wants to get to the other side and equalize the temperatures. Insulation materials are designed to stop the flow of heat. The R-value is just a measurement of how well the materials are working. In garage doors, the higher the R-value the better the door will be at stopping heat loss.

Do different insulation materials affect the R-value?

Some materials provide better insulation than others. Polystyrene (styrofoam) and polyurethane (spray foam) are commonly used forms of insulation in garage doors. They are similar materials, but work differently, and provide different levels of protection.

Polystyrene is inserted into garage doors in panels and therefore cannot be an exact fit. This means there is room for air to get in. Polyurethane is sprayed into the door. The spray foam expands and is able to bond to the surface. Because it is bonded to the surface, the spray foam will also help insulate against outside noise, making a quieter garage. As can be expected, the R-value is much higher with polyurethane.

How is the R-value measured?

You can calculate a theoretical R-value if you know the materials used in construction. Common building materials have already been tested and have been assigned an R-value. These can be found online and totaled to come up with theoretical R-value.

Why should the R-value matter to you?

This is the question that you should really be asking when shopping for a garage door. The R-value can help you determine how efficient a garage door will be at insulating your garage and home.

Heating your garage all winter can be expensive, so if it’s not going to be used too often you may not need a high R-value garage door. Heat that escapes through the garage door is money down the drain. However, if you use your garage as a year-round workshop or you have rooms around and above the garage, then you will want to look for doors with high R-values.

What R-value should you look for in a new garage door?

Higher is better when looking at garage door R-values, but it’s not the only factor to consider. Today’s garage doors with polyurethane insulation will have an R-value of 12-18 (Garaga’s residential garage doors provide up to R-18), but you also want to choose a door that has otherwise good construction.

The bottom seal, weather stripping, and the sealing joints between panels are also very important to consider when choosing your next garage door!

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