What R-Value Do I Need For My Garage?

R-Value. Sounds like something out of a physics book, right? And in a certain sense, that actually would be a likely place to find it. Where else should it be mentioned? Garage R-Value is something you need to know about.

Unlike measuring the density of states for electromagnetic radiation, which you’re probably not going to be interested in unless you actually are a physicist, R-Value is something that has an impact on your home and you need to be aware of it.

Here in this article we’ll help you get a solid grasp on what R-Value is and what sort of R-Value you will need for your garage.

R-Value Defined

If we want to get technical, R-Value is the temperature difference per unit of heat flux needed to sustain one unit of heat flux between the warmer surface and colder surface of a barrier under steady-state conditions.

Super helpful, right?

A better way of stating it is that R-Value is a measure of resistance in heat-flow through a given thickness of material. So think about your walls, R-Value would be the measurement of how well those walls keep heat from transferring either in or out.

R-Value, therefore, stands as the primary industry standard for measuring the capacity of insulation.

R-Value for the Garage?

You might be saying at this point, “Listen, I get it – R-Value is a measure of insulation and I need to have insulation around my house. But, what’s this got to do with my garage?”

The short answer, a lot.

You know your home needs to be insulated, otherwise you’ll be blazing in the summer and freezing in the winter. Plus you’ll be losing tons on your energy bills.

So it’s fairly self-evident that you need to insulate your living area – but it’s also vital that you insulate your garage. There are two main reasons why.

First, you might not live out in your garage but your vehicles probably do. And temperature has a big impact on how well they start-up. Just think about the last time you left your car out in freezing temperatures; slow to start and slow to warm. Treat those vehicles well and make sure your garage is insulated!

Second, you need to think of your garage as not only being the place where you park your vehicles but also you need to imagine it as being an extra layer of protection for the house itself. The air in you garage acts as a buffer between the untreated exterior air and that precious (and expensive!) treated air within your home.

R-Value Within Your Garage

The reality is there isn’t just one single R-Value worth of insulation that you need to focus on when it relates to your garage. Rather, your garage is composed of different component elements that will need different levels of R-Value applied to them.

Exterior Garage Walls

Let’s start with your exterior walls since these will comprise a large portion of your garage. Typically these will be constructed from standard 2-by-4 studs which will define the amount of insulation that you can have installed.

You should be targeting an R-Value of R-13 or R-15 in these areas to properly maximize your insulation in this application.

Garage Ceiling

Next, on to your garage’s ceilings. Here, the level of R-Value you apply is largely going to depend on whether or not you have a finished room over the garage.

If you do, this is going to be resting on joists and will give you roughly 10 inches of play in which you can apply high-density R-30 style insulation.

On the other hand, if your ceiling just goes straight up to the rafters, you’ll have even more space and can apply stouter R-38 insulation between the rafters and the roof.

Garage Door R-Value

Finally, onto the garage door itself. This is a pretty vital step, even if the amount of R-Value you can apply is limited, because without having this installed, any treated air that you have present in the garage will get sucked out through the door.

Typically, you’re only going to be able to apply insulation with an R-Value of around R-8 or R-12 to the door. This is due to the limited amount of spacing that’s available on the back of the garage door; anything thicker will impede the performance of the door itself.

For the door, you’ll want to be on the lookout for a special, and thinner, foil-backed insulation that you can affix to the backside of the door.

However, if you know that you’ll absolutely need to bump up your insulation level on the door, there are pre-insulated garage doors on the market that come with a higher level of R-Value (just bear in mind that these are going to come with added costs).

Two Types of Insulation

We’ve talked our way around insulation throughout this whole article – let’s get a quick snapshot of the two main insulation types that are available on the market.

First, there is polystyrene. You’ll most often see this being used in foam cups and in different packaging applications. But, it also gets used on garage doors. While it does have its place – it’s not the type of insulation we would recommend.

Polyurethane, that’s the better option. This type offers a higher R-Value on the whole and is far more easily applied. Its sturdy composition ensures lasting, quality insulation. Due to all of these factors, we definitely recommend this as being the insulation of choice.