Should a Garage Roof be Insulated? Everything you Need to Know

Garage insulation has been a topic of interest for a long time. That’s because there are different opinions from homeowners and building contractors about it. Whether or not you should insulate your garage roof ultimately depends on how you use your garage. And in this article, I’ll explain the instances where it’s essential to insulate the garage roof and cases in which it isn’t. Let’s get into it.

Insulating your garage roof may be unnecessary if you only park your car in the garage. However, if you spend a lot of time in your garage, it is an excellent idea to insulate the garage roof and the garage walls. That’s because it will help keep the garage at a moderate temperature in all seasons and reduce heating and cooling costs.

Let’s take a look at some compelling reasons why you should definitely insulate the garage roof. And then, after that, we discuss when it may be unnecessary to insulate the roof. Later in the article, we will discuss some other vital factors to consider when you want to insulate the roof.

Reasons Why You Should Insulate the Garage Roof

These are the benefits you’ll get by insulating the garage roof.

It will help keep the garage at room temperature.

During the summer or in a hot climate, all that heat from the sun is absorbed by your garage’s roof. And it doesn’t end there. Because heat always transfers from a higher temperature region to a lower temperature region, all that heat on the roof gets transferred into the garage, or the attic, if you have a ceiling installed.

This can make your garage extremely hot, and you wouldn’t want to waste a second there. 

In the winter or a cold climate, the situation is different. Since your garage will be warmer than on the outside, the warm air in the garage will be transferred outside by virtue of heat transfer. It can be transferred through the garage door, walls, and roof. And in no time, your garage will be at freezing temperatures. 

Insulation fixes this problem. How? Insulating the garage roof will prevent heat from transferring from the roof into the garage during the summer and prevent warm air in your garage from being transferred outside through the roof, keeping your garage at a stable temperature. In essence, insulation materials serve as a barrier that doesn’t permit heat to move through them. 

If you are converting your garage into an office, a workshop, a gym, a laundry room, or any space that will make you spend more time in the garage, I highly recommend insulation. 

If you are serious about keeping your garage as comfortable and habitable as possible, you shouldn’t insulate only the roof but the garage walls and the garage door as well. This will help keep heat out of your garage and prevent cold air from seeping in from all angles.

It will reduce garage heating/cooling costs.

If your garage is included in your home’s HVAC system, you must insulate the garage roof. Here is why.

As you probably know, our homes’ HVAC system is meant to artificially heat and cool our homes into a comfortable temperature to live in. To keep all that hot or cold air generated by the HVAC system in your living space, it’s important to insulate your home, or in our case, the garage.

If your garage is uninsulated, all that air produced by the HVAC system will escape through the roof, walls, or doors. This will keep the HVAC system working continuously in an attempt to achieve the temperature you require. But that’s never going to happen, and this will drastically increase your heating and cooling costs. 

Think of it this way. If you’re heating an uninsulated home, then you are pretty much heating your entire neighborhood. That’s because your home is not thermally separated from the outside.

So, to keep your garage heating and cooling costs at a reasonable rate, it’s essential to insulate your garage roof.  

Insulation adds value to your home.

If you have plans for selling your house, insulation is an excellent way to increase your home’s value. The better the insulation of your home, the higher the value. 

The general notion is that if the home is thermally conditioned and insulated, you spend less on heating and cooling in the long run. So it is worth the extra cost.

It’s definitely worth the effort insulating your garage, including the roof, to make your home thermally efficient. 

Reasons not to Insulate a Garage Roof.

As we have already discussed, insulation is an excellent way to separate your home from the outside thermally and helps keep the temperature inside bearable and comfortable. However, there are instances where they are simply not necessary. Let’s take a look at them.

If the garage is used as a parking space

As you already know, the garage was made to store our vehicles. It is not designed as a room to dwell in. This is why most garages have no windows or vents. I explained this concept of garage ventilation in this article. I recommend you check it out.

If the garage is used as a parking space, you will spend a relatively short period there. You will simply park your vehicle in there, and then move into your living area.

If that’s how you use the garage, it’s unnecessary to insulate the garage or even the roof. That’s because whether the garage is hot or cold, you wouldn’t spend enough time there to be uncomfortable. 

The only downside is your car’s interior may get extremely hot in the summer when you park it in there. This may be a deal-breaker to some people, but to me, it’s not as such an issue. That’s because all that hot air will be blown out by the wind when I move outside the garage.

It is not required by code.

It is not a requirement by the International Residential Code to insulate your garage or the wall. According to the code, the garage is considered a utility room. It is made to store equipment and machinery such as vehicles. Storage rooms require no insulation or ventilation according to the code. 

For this reason, any insulation, conditioning, and ventilation of your garage to make it as habitable and comfortable as possible is simply a matter of choice. 

So as I explained in the previous section, only insulate your garage if you are going to spend a considerable amount of time there, reduce heating or cooling costs, and add value to your home because there are no building regulations that require you to insulate your garage. 

Recommended Insulation Materials for a Garage Roof

Suppose you have decided to insulate your garage roof, excellent. Now, there are different types of insulation materials available today. They all have their pros and cons. However, I’ve found these three types of insulation materials that work exceptionally well for garage roofs and roofs in general.

Spray Foam Insulation

Spray foam is one of the best options for insulating a roof. It is made of polyurethane, a popularly known insulation material even used on some garage doors. Just as the name depicts, spray foam insulation is sprayed directly under the roof. Which means there is no space between the insulation and the roof for condensation.

The foam provides another layer of thickness to the roof to make it even stronger. So it doesn’t only insulate your garage roof but makes it last longer as well. With a spray foam used under your roof, you are guaranteed to save at least 20% on heating and cooling costs.

The only downside to spray foam insulation is, it is not DIY-friendly. You need to hire an expert to insulate the roof for you. And the cost will depend on the dimensions of the roof that needs insulation.

Fiberglass Insulation

You have probably seen fiberglass insulation before. That’s because they are the most common insulating material. They are also the recommended material for insulating the entire garage as well. 

It slows down heat transfer drastically because glass is a bad conductor of heat. It is the go-to for many building contractors because it is the most cost-effective option out there. They are relatively easier to install as well, and very eco-friendly. 

Rigid Insulation Boards

These are insulation boards that come in predefined sizes. The dimensions are 4′ x 8,’ and the thickness varies between ½” and 4″. To properly make it fit between your roof rafters, you may have to cut them in the right sizes.

One thing I like about these boards is they give a professional-looking finish after insulation. So I recommend it for homeowners converting their garage into an office, a gym, or a living area. 


Ultimately, you want to insulate your garage roof if you will spend a lot of time there. It will keep the heat and cold out, keeping your garage at an optimal temperature. Insulating the garage roof and walls will also reduce the garage’s heating and cooling costs if it’s part of your home’s HVAC system.

Related: Does a Garage Attic Need to be Vented?

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