How to Insulate Garage Walls That Are Already Drywalled

A complete and detailed guide

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If you have a brand new garage that already has drywall installed, you might find it challenging to find out how those walls could be insulated. See, in some states, it is mandatory for the garage owners to insulate their garages, so if this is your case, you might want to figure out how to do that when you already have drywall on your interior garage walls!

In this article, we will tell you how to insulate a garage wall without removing the drywall. In addition, you will learn what tools you will need for that procedure. Moreover, we will provide you with a detailed guide where you will find a step-by-step description of the entire process! In addition, we will tell you more about how to keep your garage cool.

With all this in mind, you will be able to upgrade your garage and make it not only useful but also a very comfortable place for keeping your car there. 

How to Insulate Finished Garage Walls


Worker preparing to insulate garage

If your garage walls already have drywall on them, you might find it challenging to insulate them. And if insulation is mandatory for you due to the law, you will have to find a way how this can be done. So how is it possible to insulate garage walls without removing the drywall? First of all, you need to get ready for the upcoming procedure and prepare all the tools and appliances you will need.

  1. Blown-in insulation
  2. Blower machine
  3. Drill with a hole bit
  4. Stud finder
  5. Drywall repair kit
  6. Paint primer
  7. Interior paint
  8. Protective suit

Once you get all these things ready, you can proceed to the insulation installation procedure. In general, the process of installing insulation will consist of several steps:

  1. Find the stud locations
  2. Drill access holes
  3. Install the insulation
  4. Seal the access holes

Of course, before you insulate the garage walls that are already drywalled, you need to do some preparations. For example, it is important to measure the space of the walls of your garage. Like this, you will be able to make sure that you buy the right amount of insulation. At this point, you should also note that the ideal type of insulation to use will depend on several factors: 

  • Your budget
  • Your preference
  • Any applicable local building codes

And now that you are more informed about the general sequence of actions and the tools needed, let’s move on to the insulation application process.

Find the Stud Locations

After you have bought all of the tools and equipment needed (see the list above), you will need to locate the stud locations first. You can do this easily by using a stud finder. This tool will prevent you from drilling access holes directly on top of the studs that are holding the walls in place.

The process of stud holes spotting is very easy: 

  • Start in the upper left corner of the first wall that you plan to insulate
  • Work your way to the right, marking each location with a pencil.

You might be curious about the number of holes that you will have to find and drill later. The number of holes needed for insulation will depend on the size of your garage. By the way, note that most garages in the U.S. are around 20 x 20 feet. Also, you should note that the wall studs will typically be anywhere from 16 to 24 inches apart.

Drill Access Holes In the Walls

After you located all the stud holes, you can proceed to the hole-making process. Before you start drilling, you need to place a drop cloth beneath the wall that you will be drilling the holes into. The drop cloth will make the cleanup process much easier afterward. 

Now, you can start. Using a drill with a hole bi, create a 2-inch hole in the top portion of the wall at each pencil mark. At this point, you need to be sure to set the piece of drywall that you remove in a nearby location so that you can reinstall it later. 

It may happen that the piece falls inside the wall, but don't stress out! You can fill in the area later easily. Simply keep on working your way from left to the right, creating an access hole every 3 to 4 feet.

Install the Insulation

After you are done with drilling holes, put on your protective equipment, and proceed to the insulation application process. Start with placing your blower machine in position and ensuring that it is close enough to the spot where you can reach the hole with the hose. 

Then, put the end of the blower hose inside the hole while an assistant turns the machine on (yep, it’s good to have another person helping you, by the way!).

When working with the blower machine, make sure that the hose is placed as far down as possible in the wall. As the wall cavity begins to fill, pull the hose out slowly, moving inch by inch. We recommend you work slowly because like this you will ensure that the entire wall cavity is tightly and thoroughly packed with an even layer of insulation. You don’t want to have gaps and empty spaces there for sure!

When you start to feel resistance with the hose, ask your assistant to turn off the blower machine. Then, carefully remove the entire hose. Basically, this process has to be performed for each hole that is drilled into the wall. Also, you will have to repeat the same process for the other three walls.

Seal The Access Holes

After you finally fill all of the garage walls with insulation, it is time to seal the holes that have been made in the drywall. If you were able to keep all of the drywall pieces, you can apply adhesives to the edges of the holes and place them back in the wall.

When doing so, be sure to let the adhesive dry halfway before you place the pieces back in position! This will prevent them from falling inside the wall and will help them to dry in place faster.

If it so happened that you didn’t manage to keep the pieces from falling inside of the wall, there is still nothing to worry about. Simply patch the wall using a drywall repair kit. Then prime the repair areas and paint them.

Like this, you now have all the walls of your garage insulated. Having insulation on your garage walls is anyway a good idea! For example, insulation can reduce the amount of heat transfer that often takes place inside your garage walls. Even if you simply insulate the ceiling or the walls alone, it can make a huge difference!

Of course, the time of year when insulation will be most beneficial is in the spring and summer months. This is the period of time when the weather is the warmest (especially in summer) and the amount of heat is the highest. It will also be beneficial to add insulation to your garage door to prevent heat from getting into the garage space. 

What Is the Cheapest Way to Insulate a Garage?

Many homeowners believe that insulating a garage is pretty expensive. This is why quite many of us prefer keeping our garages without insulation and thus suffer from constant heat inside. But if you are looking for a way to insulate your garage and spend as little money as possible for that, there are a few ways to do it. In addition, you can do it both cheaply and with proper quality. 

To begin with, measure the space you plan to insulate in your garage. For example, you might only be looking to insulate the garage walls or the garage door. Also, consider whether you plan to insulate the ceiling as well. You need to have a clear idea of what you are willing to have and what you are ready to spend. In addition, you need to know for sure what areas will be covered. Below, you can check out the most common types of insulation that can be used on a budget.

Fiberglass Batts And Rolls

Fiberglass batts and rolls belong to the most popular type of insulation in the majority of homes. And this is a reasonable choice! This type of insulation is not only effective, but it is also one of the most inexpensive ones that you can purchase! 

The prices are also very affordable and pleasing for your wallet. On average, if you are going to use fiberglass batts and rolls for insulating your garage, plan to spend about $0.30 to $1.55 per square foot for this type of insulation.

Another benefit that this insulation type has is that you can easily install it yourself, thus saving on contractor costs. Fiberglass batts can easily be installed on your garage walls. All you have to do is simply cut them to size and place them directly in between the joists.

If you need to install this type of insulation on the ceiling, you will basically use the same method. However, we recommend you use adhesive or staples to secure the fiberglass bats in place.

Rigid Foam Panels

This is another affordable option for insulation. Rigid foam panels, also known as polyisocyanurate insulation, can be used on both the walls and the ceiling. In addition, their installation process is pretty much the same as that of fiberglass batts. 

You will need to cut the boards to fit in between the joists, and they will also need extra security if you plan to install them on the garage ceiling.

Rigid foam panels can be especially effective if you live in regions with cold weather and climate, as they have a higher R-value per inch. The only insulation type that has a higher value per square inch is mineral wool (you might also hear about it as "Rockwool"), but it is also more expensive.

Like this, you are now aware of the cheapest types of insulation that can be used on your garage walls, and even door and ceiling. However, don’t think that low price means low quality! Both types of insulation we described here provide great quality insulation which means that you can get the best for the lowest cost.


What to Do to Keep Your Garage Cool All the Time

As you already know, insulation can contribute to keeping your garage cooler inside which is especially valuable for those who live in areas with a hot climate and high temperatures. Keeping a car in a constantly hot garage is definitely not the best idea!

This is why we decided to share a few handy tips and life hacks with you. With their help, you will be able to keep your garage cool inside easily. 

Let Your Car Cool Off Outside

Well, this recommendation will be helpful both for car owners and motorbike owners. During the warmer months of the year, simply park your vehicle outside before placing it in the garage for the evening and night. 

By letting the car or motorbike cool down for about 15 to 20 minutes outside, you will help the heat radiate from your vehicle within minutes! As a result, you will allow the garage to stay cooler on warmer days. If you place the vehicle into the garage at once, this will not happen though.

Add Fans To The Garage

Fans can be another inexpensive way to keep your garage cool. All you need to do is simply add one or two fans. They will help with ventilation, and in addition, they are much cheaper compared to installing an air conditioning unit for the space!

In order to create more airflow in the space, you can even use two different fans! Also, if you are using your garage for both parking and recreational purposes, keeping a high-power shop fan there will definitely make a difference when you are in the garage working or hanging out!

Paint The Garage With Light Colors

Everyone knows that light colors help reflect sunlight better than dark ones. It happens because light colors (for example, whites, light beiges, light gray, or light blue) bounce the sunlight off the garage walls instead of absorbing it. As a result, walls get less hot. This can make a huge difference and keep your garage a bit cooler on the hotter days of the year.

It can also be helpful to choose a garage roof with lighter colors or install a few solar panels on top of it. If you live in the south or western part of the U.S. and have a garage that faces the west, this will definitely make a difference.

Well, now you are completely informed about all the nuances, factors, and tips regarding garage wall insulation! We told you what tools you will need for that, how exactly the application of insulation should be done, and you even learned how you can help your garage cool down faster! With all this in mind, we are sure that your garage will become way comfier for both keeping vehicles, working, and hanging out there!

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