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Time Needed: 1-2 days, Difficulty: Beginner, Cost: $250-$625 per 500 square feet (materials only)

When I finally got a house with a garage, I was excited to have a space for working on projects out of the elements all year. However, cold, harsh trouble is always on the horizon when you live somewhere with ever-changing seasons, and that handy workspace doesn’t exactly meet expectations when you have to bundle up and wear gloves. After all, wind, snow, and rain aren’t the only elements, and good insulation will make a world of difference. 

If, like me, you’ve been thinking about adding a heater to make your garage a true year-’round workspace, then insulating the interior is a great next step. And whether you want to heat and cool your garage, or just heat it in the winter with a permanent or as-needed solution, then insulating the garage is worth the up-front investment. Insulation slows the transfer of heat from inside your garage to outside, so if you have a heating system in your garage now, and it’s not insulated, then get ready: Things are about to work a lot better. 

Don’t get discouraged when you look at the bare two-by-fours in the garage, as adding insulation to a garage is pretty straightforward. And it doesn’t take more than a day or two to get it done. So if you’ve been thinking about doing just that, let’s get after it and make sure your garage stays warmer for longer. 

The Safety Brief

Because this project involves ladders, basic tools, and a lot of moving around, it’s not without some danger. Follow general safety advice when working in the garage or crawling around in the attic. 

You’ll also have to watch your head around the roofing nails coming through the roof, and be careful when climbing the ladder to get up there. And, if you decide to go with fiberglass, you have to be careful with this stuff in all its forms: Fiberglass is an irritant to skin, eyes, and lungs (Ed. Note: I once spent a week trying to get insulation out of my skin and hair after a short job in an attic. Always wear protective clothes!). You’ll want safety glasses, a respirator rated against fiberglass, and long sleeves to go with your gloves.

For myself, I went above and beyond reasonable and used a fitted 3M respirator with P100 filters to blow insulation into my attic. I also had a Tyvek suit to keep the itchy stuff out. If you don’t want to spring for a fancier mask, get a minimum of an N95 respirator, long sleeves, and work gloves. 

The Tools & Parts You Need

Insulating a garage is one of those projects that won’t require a bunch of specialty tools. The cost is largely related to the amount of insulation you use, what kind you go with, and then how you finish the garage off. Though finishing it isn’t the main point of this article, what you put over the insulation will play into things. 

I haven’t made any assumptions about what you have and don’t. I have a few things, but my tool collection skews towards the automotive side, too. Buy, rent, or borrow. 

What’s more, getting most of the way done, then stopping to run back to the store can be a huge waste of time. I bought more insulation than I knew I needed and returned the rest when I was done with the project. Many building supply stores will include the rental of their insulation/cellulose blower if you buy a certain amount of insulation from them, so be sure to ask them to show you how it works before you leave.

The other most important thing to line up is some help. If you’re going to blow insulation into the roof of your garage (or the walls), then you’re going to need someone to feed the material into the hopper while you point the hose where it needs to go.

The Task: How To Insulate a Garage 

Just like working on your automotive projects, a little preparation and planning go a long way when insulating a garage. This is a project that you can finish during a weekend if you get all your supplies together during the week. Block out the first part of your day to do the stuff that requires equipment rental — like an insulation blower — and then tackle the rest of the job.

1. Prepare the ceiling for blown-in insulation.

You need to have a clean and clear work area. If you want to blow insulation into the attic space, make sure you clear out the junk you have up there. If you start on this during the week, use the opportunity to throw things away that you don’t need.

2. Clear the walls for insulation.

Wall studs need to be free of nails and should be clear of anything not strictly necessary so installation is as straightforward as possible. Wiring can stay, but remove as much as you can so you’re not working around shelves and hooks.

3. Look for gaps and cracks in the wall.

Make a plan and fill in any gaps you see, especially those that you can see daylight through. Every crack is a place for a draft, pests, or water to get in. Use expanding foam in a can, such as Great Stuff, for this job. Do this a few days before you get to the actual insulating work so it has time to cure.

4. Familiarize yourself with the insulation blower.

I’ve worked with heavy machinery for too long to not give you a safety talk! Even though you remember the salesman’s spiel, get the machine plugged in, switch it on and off a few times and familiarize the person who will be running it (your helper!) with how to turn it off in a hurry, and how long it takes the agitator to stop turning. Keep your hands, feet, and arms away from it. Keep a stick handy while feeding insulation or cellulose into the blower in case something needs to be pushed down.

Now is the time to “suit up.” Get your respirator on, get your gloves on, and cover up your arms and legs before you bust out the itchy stuff. Also, watch your head — those nails in the roof can be painful.

Austin Lott

5. Start slow, then get it done.

Get a feel for the hose and how to get it far enough back to get insulation into the corners of the ceiling. Have your helper feed in about half a bag to get you started. It’s not a violent process, but the insulation or cellulose does come out pretty quickly. Once you have the hang of it, bang on the rafters and tell them to let ‘er rip! I have a 550-square-foot garage (two-car) and this process took about an hour and a half once we got going.

If you have light fixtures that stick up into the ceiling, or a chimney that runs through it, keep insulation 3-5 inches from them. If it’s too close, it could cause a fire.

6. Pack up the machine (and return it if you have a time limit).

I had my unit for the whole day, with no strict time limit. If you’re renting, or have a stricter window, this is the time to take that insulation blower back. Even if you don’t have a time limit, clearing your garage of the hose and machine will make the rest of the insulation work that much easier.

7. Install fiberglass insulation.

Start with the odd sizes and shapes and cut pieces to fit out of a batt. Staple them to the face of the board as needed to get the insulation to stay in place. Use a utility knife to slice the fiberglass and lay wiring in the insulation. You want to avoid air gaps in the insulation, which can reduce its effectiveness.

8. Add a vapor barrier (if desired).

This is often as simple as sheets of plastic. It’s installed on the “warm” side of the insulation and is usually installed before drywall.

9. Insulate the garage door.

This one is pretty simple: follow the instructions on the kit you bought.

10. Cover the insulation with drywall.

There are a lot of reasons to install drywall, or another rigid material, to finish the garage. If you used unfaced fiberglass batts (those without a paper or plastic backing on one side), an air barrier is necessary for the performance of the insulation, and it protects all your hard work, too. My garage is finished in plywood, but that’s from several owners ago. 

Austin Lott

FAQs About Insulating a Garage

Car Bibles answers all your burning questions.

Q. Can I just insulate the garage door?

A. Insulating a garage door can cut down on noise, but on its own, and without insulation anywhere else in the garage, it won’t make a big difference in keeping the garage comfortable. 

Q. How much will it cost to insulate a garage?

A. It depends on how much you do yourself, what materials you choose to use, and how big your garage is. A one-car garage could easily be insulated for about $500, while a two-car garage would likely come in around $800 to $1,000.

Learn More About Insulating a Garage From These Video Tutorials

We know not everyone is going to learn the process just from reading, so we found a couple great videos to show you some of the right techniques for the tricky parts. Though this video is obviously dated, Part One and Part Two go into not just the right ways to install insulation, but they show you why things don’t work well by testing. The third video is from Home Depot and features a popular insulation kit. 

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