How To Insulate A Garage [Walls, Roof & Door Step By Step Guide]

Garages are notoriously chilly places.

You might store items in there or have your utility appliances out of the way. It might even be your home gym.

If you do spend time in your garage, you’ll want it to be a comfortable space. Insulating the garage will help you to make it a more habitable room all year round.

Not only that, but it’s also a great way to prevent moisture and noise from finding their way into your house. You’ll even increase your property’s resale value! Win-wins all around.

So here’s a step by step guide on how to insulate a garage.

What you need for this project

To save yourself the hassle of going back and forth while on the project, gather all of the necessary tools and materials to get the job done from the start.

Here’s what you’ll need.

Necessary tools

Let’s start with the necessary tools for inspection, installation and protection (keep in mind that you might need additional or fewer tools depending on how you execute the project):

• Screwdriver
• Prying bar
• Hammer
• Drywall screws
• Utility knife
• Staple gun
• Caulking gun or expanding foam (for air sealing)

Insulating materials

In addition to the tools, you’ll also need to choose the right insulating materials for your garage. When it comes to wall and roof insulation, there are various materials to choose from, such as fiberglass, foam (spray or rigid) or cellulose.

For this project, we’ll focus on fiberglass insulation because it’s quite affordable with a decently high R-value (insulation factor) all the while being easy to cut and DIY-friendly. There are many of types of eco insulation you can choose from though.

Keep in mind that fiberglass can be a lung and skin irritant, so make sure that you wear protective long-sleeve gloves, a filtration mask and glasses while handling or cutting them.

As well as your insulating material, you’ll also need:

• Waterproof membrane sheets
• Drywall or plywood
• Garage door insulation kit (optional but highly effective and saves you a lot of trouble)

With that in mind, we’re going to look at the 3 main areas when insulating your garage:

• Walls
• Roof
• Door

How to Insulate Garage Walls

With all the necessary tools and materials prepared, here’s what you need to do to insulate your garage walls.

Step 1: Prepare the walls for insulation

Start by removing anything hanging on the wall, including utility boards, tools, ladders, hooks, nails etc. You might need a pry bar and a hammer or a screwdriver to get the job done.

After removing the items and tools hanging on the wall, you should clear up any dust or dirt on the wall.

Additionally, remove any drywall panels that already exist so that you get access to the bare wall studs. If you just have a breeze block garage, you’ll have to install wooden batons or a stud wall so you can slot the insulation inbetween.

This should also be a good time to check the wall for signs of mould or moisture damage. Make sure that you fix the walls before insulating them for maximum efficiency.

Step 2: Seal any cracks or gaps in the walls

For more reliable insulation, you should seal any gaps in the interior or exterior walls of the garage.

This prevents the flow of heat, moisture and pests through cracks, which leads to the failure of insulation, mould growth, infestations and water damage.

Using a torch, scan the walls carefully and look for any cracks to seal using a caulking gun. Apply the sealant but don’t overfill the gaps because the foam expands.

After that, allow the sealant to cure and dry completely before going ahead with the insulation (should take around 6 to 9 hours).

Step 3: Install fiberglass insulation to the walls

Installing the fiberglass is the most critical part of your insulation, so make sure that you cut it properly to fit the distance between the sides of the studs using a utility knife.

To do that, gently tuck the fiberglass insulation into the required space, then put a piece of wood on top, and run your utility knife over the excess fiberglass so that it’s sized correctly.

If it’s a snug fit, you won’t need to staple or fix the insulation in place.

Step 4: Add waterproof membrane and drywall to finish

Leaving the face of the studs exposed in the previous step is important for this one, as you’ll use them to staple the waterproof layer to the insulated wall.

Check the vapor barrier for damage, then roll it over the walls and fix it using a staple gun to the face of the studs, then remove excess with the utility knife.

Make sure that you cover the paper side of the insulation properly because it can be a fire hazard.

Finish by reapplying drywall using glue or coarse-thread drywall screws, placing them 6 to 8 inches apart.

You can also nail plywood sheets in place, which is a good cost-effective and more sustainable measure.

How to Insulate a Garage Roof

Insulating the ceiling is as important as the garage walls because it blocks the flow of heat and noise from escaping upwards.

Here’s how to properly do it.

Step 1: Prepare the garage roof for insulation

Start by cleaning the garage ceiling just like the walls. You might need a ladder or scaffolding along with a helping hand to pass the items and keep the ladder/scaffolding stabilised as you work.

Make sure that you measure the length and width of the ceiling properly and do your calculations to get the required sizes of insulation batts and cut them to the proper sizes.

Step 2: Fit the insulation batts to the ceiling

Start by fitting rafter vents over the rafters, and use a staple gun to secure them into place. The staples should be around 6 to 10 inches apart.

Next, you’ll install the insulation batts onto the ceiling between the rafters and make sure that you cover the entire surface.

Any uncovered corners or crevices must be sealed with expanding foam.

Step 3: Apply waterproof membrane barrier and drywall/plywood over the insulation

Once the ceiling is fully covered with insulation, you’ll need to cover it with a waterproof barrier for additional protection from moisture.

Simply roll out the membrane sheets and staple them over the insulation with staples 6 to 8 inches apart (make sure there aren’t any gaps or tears in the vapor barrier).

Lastly, you should finish up the ceiling with plywood or drywall to cover the insulation and improve the aesthetics of your garage.

If there are any gaps in the roof, use caulk or tape to make sure these are covered up.

How to Insulate a Garage Door

For optimal protection against noise and exterior temperature, you also need to insulate the garage door.

The easiest way to do it is by using a garage door insulation kit, so here’s how to use it.

Step 1: Clean and measure the garage door panel

The garage door is exposed to a lot of dirt and grime, so make sure that you clean the door before you start using a household cleaner and a clean rag.

After hosing down the garage door, make sure that you let it dry for 4 to 6 hours before insulating it.

Step 2: Measure the size of the garage door panels

While the garage door is drying out, you can use the time to measure the dimensions of your door with the help of a tape measure.

This is essential to buy the right size of garage door insulation kit.

You should also measure the size of each panel, so you’re able to cut the insulation batts to a suitable size while applying the insulation to the door.

Step 3: Install retaining pins onto the Panels

Make sure that you invest in a premium quality kit with a high R-value.

Most kits will come with large insulation batts and retaining pins with fasteners to keep them secure.

You’ll need to install a retaining pin for each panel on your garage door. The retaining pins usually come with a peel-off glue base to stick them to the center of the panel.

Step 4: Cut and install the insulating batts

With the retaining pins in place, all you need to do is cut the insulation batts with a knife to match the size of your garage door panels.

Simply press the foamy batts firmly into the retaining pins then tuck the remaining part of the insulation into the metal railing on the door.

With a precise fit, your batts will fit perfectly.

Step 5: Secure the batts with fasteners

Once you’re done installing the insulating batts, use your hand to find the location of the retaining pins, then mark these spots by making small incisions at the tip of the retainers.

After exposing the tip of the retainer, you can secure the batts using the retainer fasteners to keep everything in place.

Wrap up on insulating a garage

There you have it! A simple guide that shows you how to insulate a garage, including its walls, ceiling and doors.

It’s important to make sure all rooms in your house are fully insulated if you want to save on energy costs and create a comfortable living environment. There are simply home insulation tricks you can put in place too.

Rooms such as conservatories are notorious for the heat extremes – cold in the winter and hot in the summer.

If you have one, read up on how to insulate a conservatory here.

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