How To Insulate Finished Garage Walls (in 5 Steps)


There are many great benefits that home insulation can provide you with. From financial benefits that arise from a lower energy bill to a reduced carbon footprint, the list goes on. However, if your walls were finished before you could insulate them, it’s never too late!

Insulating finished walls is possible with the use of cellulose insulation. The process is carried out by cutting holes between studs in your finished wall with a hole saw. Following this, you use an insulation blower to fill your existing walls with insulation before refitting the pieces of wall you cut out. The equipment you need can be rented to save on costs.

In this article, we’ll look at the home insulation process and how it differs depending on your walls’ state of construction. After looking at the benefits of insulating certain areas in your home, we’ll break down what you need, how to get it, and how to insulate your walls in five simple steps.

Can I Insulate Finished Garage Walls?

When it comes down to insulating walls, there are many factors that you need to keep in mind. From the state of the walls you wish to insulate to budgetary concerns regarding insulating your home, it can feel like an overwhelming process!

Insulation is a type of material that is used to insulate something, typically a building, in order to provide certain thermal properties. The fantastic thing about insulation is that it works both ways: it reduces both heat loss and heat gain, depending on the season.

In general, the main purpose of insulating walls within buildings comes down to the thermal properties the insulation material provides. In fact, there are many other surprising benefits that come from insulating your home – but we’ll get to that.

When insulating your walls – regardless of which method you use – the material you use will have what is known as an R-value. This rating gives you an indication of the ability of the insulation material to resist the conduction of heat. You should keep this rating in mind when deciding on insulation material.

As a general rule of thumb, the higher the R-value of the material, the better it will insulate. If you live in a rather cold region, you’ll want to get insulation material with a higher R-value than someone living in a warmer climate.

When you’re buying insulation material, you can speak to a consultant to ensure you get material that will adequately insulate your home. This will allow you to utilize the full advantages that insulation can provide. However, there’s another important aspect to think about!

One of the most important considerations to keep in mind when insulating walls is the construction state of those walls. Are the walls you wish to insulate still under construction, or are they already completed? Chances are if you’re reading this article, those walls are already completed.

If those walls you want to insulate are, in fact, already completed, you don’t have to worry about resorting to drastic measures such as tearing the drywall down in order to insulate. Luckily, there are easier ways to insulate finished walls!

For garages with unfinished construction, the most popular insulation material would be fiberglass roll insulation. For garages where the construction is already complete, cellulose insulation would be the material to use.

Cellulose is made primarily from newsprint that has been recycled and provides excellent thermal properties when used as insulation material. The reason this material can be used after a wall has already been completed is due to the fact that his cellulose fill is blown into existing walls until these walls are tightly packed with cellulose.

This means that, with this type of insulation, you can top up your wall’s insulation with more cellulose in time. Over time, the cellulose will settle, but you’ll be able to add more with ease when needed using this method. However, walls fitted with fiberglass roll before the construction was completed cannot be insulated with cellulose, too.

There are many great advantages of insulating your walls, but cellulose actually provides an extra benefit! Cellulose insulation fill is typically treated so that the material is resistant to pests, mold, and fire. Let’s jump right into some of the other benefits that insulation can provide you!

The Advantages of Insulating Your Garage Walls

There are many great benefits to insulating your garage walls – or any walls in your house, for that matter. When you consider these advantages, you’ll find it makes more sense to insulate your walls than to not insulate them. These are the biggest reasons you should insulate your garage walls!

#1 More (Cost-)Efficient Heating and Cooling 

If you’re not already aware of this, heating and cooling typically accounts for nearly half of all energy used in the average household. By insulating interior walls, you can drive down the price of your energy bill. If someone told you that by insulating your walls, you could save more than 40% on your energy bill, why wouldn’t you be interested?

By insulating your walls, you also ensure your home maintains the optimal indoor temperatures for you. In the summer, you can count on your insulation, preventing heat from passing through your walls, thus keeping your home cool. In the winter, your insulated walls will trap the heat, keeping your home toasty.

Think about your garage, specifically your garage door. In the winter, it could let a lot of cold air into your garage that could filter into your home. By insulating your garage, you could help prevent this from happening!

#2 It Helps Conserve Non-Renewable Resources

This benefit is almost a byproduct of the first one discussed! Think again about what we said above: you can save more than 40% on your energy bill by insulating your home. Insulating your walls does more than save you money on your energy bill and provide efficient heating and cooling – it helps save precious non-renewable resources!

Therefore, by insulating the walls in your home, you can reduce your overall carbon footprint! You will be directly reducing greenhouse gas emissions while conserving non-renewable resources. In this day and age, we all need to collectively help conserve these resources and our earth where we can!

#3 It Insulates Sound, Too

The list of insulation advantages goes on! Insulating walls in your home provides acoustic insulation properties that can help you in terms of sound absorbency. Depending on how many people live in your home, there can be lots of noises in your day-to-day life, from the sound of kids and dogs to a washing machine running in the background.

Insulating your home’s walls can help reduce the overall noise levels in your home – while providing many other benefits – and help you maintain your sanity. Garages can be noisy areas, from running washing machines to band practice. By insulating your garage walls, you’ll be sparing yourself a potential headache later on.

#4 It Helps Get Condensation and Moisture Under Control

This advantage is another spared headache somewhere down the line! When moisture becomes trapped within the walls of a home, it can actually result in many other issues. These include mildew, mold, and rot – which could be pricy problems down the line. Like we said, a headache.

This is particularly common in areas of the home, such as the basement and garages. By insulating these areas in your home, you can help eliminate and prevent the buildup of moisture within your home’s walls.

#5 You Don’t Pay for It, It Does (Eventually) 

With all the above-mentioned advantages of insulation, you can see that it will save you money. However, now you find yourself asking yourself how much will it cost me? Experts have estimated that, based on the amount of money your insulated walls will save you over time, your insulation installation will pay for itself within roughly five years.

When you consider how much rot damage or heating and cooling could cost you over time, it makes more sense to ‘splurge’ now on insulation. When you consider all these benefits in conjunction with one another, it makes more sense to insulate!

How To Insulate Finished Garage Walls in 5 Steps

If you’re planning to insulate finished garage walls, you’ll need to use cellulose to do that! Below, we’ll detail what you need to do this and, of course, how to do it in 5 easy steps!

What You’ll Need to Insulate Finished Walls (and How to Find It)

Due to the small particles used to insulate your wall, this can often be a messy process! You might want to keep the vacuum cleaner handy during the insulation process. In addition to that, however, you’ll also need safety goggles, as well as a mask while working with the cellulose material.

As for that cellulose material: this is how you can get your hands on it! Luckily, you’ll be able to find this locally – no matter where you are in the world. A simple Google search of ‘cellulose insulation’ will yield plenty of places for you to get it locally near you. There’s another benefit you may be able to get when buying your cellulose insulation!

Subject to where you decide to buy your cellulose insulation, they will likely also have the equipment you need to insulate your finished walls! Depending on how much insulation material you purchase, you may be eligible for a discount in renting the equipment.

Discount or not, unless you plan on regularly insulating walls, you should look to rent the needed equipment. This will likely be cheaper for you and your DIY insulation budget. You’ll need to rent a blower machine, which will come with an attached hose you’ll use to fill your wall.

In addition to this, you’ll need a stud finder in order to locate studs in your wall. You’ll also need a hole saw for this. You will also need some putty and paint to cover the holes you cut for the insulation process.

Once you’ve got your materials and you’re ready to insulate your finished garage walls, these are the five simple steps you can follow to successfully insulate your walls.

How to Insulate Your Finished Garage Walls

Step 1: Locate Studs in Your Finished Wall

When insulating a finished wall, you will need to locate studs in your wall. To do this, you’ll need to use the stud finder we mentioned earlier. Once you’ve located a pair of studs near the top of your garage wall, you’re ready to cut a hole between them. You will need to repeat this with different pairs of studs in your walls.

Once you have a pair of studs located, you’ll need the hole saw we mentioned earlier. Using the hole saw, you’ll want to cut a hole that is roughly 2 to 3 inches in width. You will use these holes to insulate your finished walls.

Be mindful to keep the sections you cut out of your wall. Once you are done insulating your walls, you will be able to reattach this.

Step 2: Get the Blower’s Hose Ready to Insulate

As we discussed briefly earlier, this can be a messy process due to the cellulose filling you need to use. However, there’s a lifehack to make the cleanup easier once you’ve insulated your walls. Once you’ve got the hose ready by the first hole you cut out, you’re almost ready to fill.

By using an old piece of material, you can wrap it around the cellulose blower’s hose. Wrap it around the hose tightly and ensure it is pressed up against the hole in your wall. This will seal the hose and prevent any of the matter from escaping while you insulate.

Step 3: Insulating Finished Walls

You might need a loved one or friend to help you out with this step! If you’re controlling the hose, have a friend turn on the blower machine for you. Once again, this ensures that there’s no huge mess you need to clean up.

As you fill the first wall through the hole you’ve created, you can retract the hose slowly as the wall fills. Make sure to move your material seal accordingly! Once you feel resistance because the wall has been sufficiently insulated, you can move on to the next hole.

Step 4: Repetition Time

Now that you’ve insulated the first hole in the first wall, you’ll need to keep going! You’ll need to repeat the above two steps for each hole you fill with cellulose insulation. Don’t worry, though: you’re a pro now!

Be sure to use your material seal to prevent insulation material from winding up all over yourself and your belongings. You also want to remember to keep those cutouts from your walls in a safe place – you’ll need them for the last stage!

Step 5: Patch and Paint Time

Your walls are now insulated and ready to be closed up fully! Simply reinsert the pieces you cut out like puzzle pieces in the coinciding cutout hole. Once you’ve done this, you’re ready to patch and paint over the few holes in your garage walls.

You’ve now successfully insulated your walls, and you’re ready for those fantastic advantages that your insulation will provide you with!

Final Thoughts

When it comes down to insulating your home, you might feel like it’s an overwhelming process. Especially when the walls you want to insulate have already been completed. Luckily for you, there’s no need to tear your drywall down in order to insulate – there’s a far easier way.


By using readily available cellulose insulation, you can insulate your finished walls. This is done by cutting holes in your wall, which are then filled with insulation. Following this, you can refit your walls with these cutouts and then patch and paint these sections.

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