How To Insulate Garage Ceiling That Is Finished

For assorted reasons, you might want to insulate your garage’s ceiling. Insulation will stop the unheated garage air from passing to any other rooms you have. Likewise, if you wish to use your garage as the extra room, you must keep cold out and warm in.

One issue is that many garage ceilings are already finished and accessing where you need to get to can be challenging. Luckily, as much of a struggle as it could be, an insulated garage will make a huge difference to the area and your utility bills.

In our guide, you can find the types of insulation material you can use. Then, once you have insulation in the roof, you can use the same techniques for insulating garage walls already drywalled. By the end, you’ll know how to do the entire ceiling using the proper methods and tackle the wall cavity or how to insulate garage walls that are already drywalled. (Learn How To Smooth Rough Concrete Patio)

garage ceiling insulation

Why Insulate Your Garage Ceiling?

You should insulate the ceiling of your garage for two main reasons.

If you want a warm or cool garage, you must insulate the ceiling. This is because the money you spend on heating the garage will escape through the roof and rise to the ceiling.

You’ll be left with a still-hot garage and less money as your energy costs are the same or increasing. Also, without the ceiling, no garage insulation job is complete.

If you have a room over your garage, all the heat from the heated garage enters through the ceiling.

Thus, the heat from an uninsulated garage is directly transferred to the room above the garage on sizzling summer days.

Because of this, air conditioning costs more inside your home, yet with an insulated garage ceiling, the heat can’t enter your home when you want to stay cool.

As a bonus, the value of your home can increase from a simple DIY job. For example, the garage roof will last longer if you insulate it, as can the walls and garage door.

Types Of Insulation Material For Ceilings

There are a few types of insulation for ceilings. Fiberglass roll or batt insulation and blown-in loose fill insulation and spray insulation.

fiberglass batts rolls

Fiberglass Batts or Rolls

Fiberglass batt or roll insulation is the most used type of insulation. It is constructed of large, fluffy rolls or batts of fiberglass fibers.

  • Batts are precut sheets.
  • Rolls are precisely what they sound like.

R30 or R38 insulation is advised for use in garage roof ceilings. The R rating shows how well it insulates. A high R-value shows it possesses higher insulation properties.

R-values increase as insulation becomes thicker. Therefore, insulation should be used that is the same thickness as your ceiling joists.

Insulation can come in bare or faced roll or batt insulation forms. Insulation that has a face has a paper barrier on one side.

Depending on where you are, you could be required by local code to use faced insulation. Verify the requirements in your local building codes before beginning any project of this nature. (Learn How To Untighten A Stripped Caliper Bolt)

Blown-in Loose Fill

Loose materials or fibers put with a blower are known as blown-in insulation. Above the drywall or other ceiling finish, it is blown into the joist cavities of your ceilings.

Installation may be more straightforward in ceilings with tight spaces that have already been completed. However, installing batts in confined spaces in the ceiling can occasionally be challenging.

Since the insulation needs a surface to rest on, it cannot be used on an unfinished ceiling.

In most cases, cellulose or fiberglass creates loose fill insulation.

  • The fibers used to make batt or roll insulation resemble those used to make fiberglass loose fill.
  • Most cellulose insulation is produced using recycled paper.

Spray Foam Insulation

An expanding spray, spray foam insulation can be applied to walls, ceilings, and gaps to fill them.

Like blown-in insulation, it must be applied to a finished ceiling to be used.

It can be used with other insulation kinds to fill air gaps or holes that are difficult to close on their own. Use closed cell spray foam to prevent water from soaking into the foam, which could cause mold.

How to Insulate a Garage Wall Without Removing the Drywall?

You can insulate the garage without removing the drywall by drilling small holes in the drywall and filling in the gap using Injection Foam Insulation or Blown-In Insulation.

Each method has its pros & cons, but both are effective and will reduce your energy cost.

Is Insulating Garage Walls Worth It?

Many people think insulating a garage implies insulating the garage door.

Garage doors are enormous and exposed to the elements.

The garage door is only one side of the garage. Three sides are walls, and you can have a floor and a roof.

Insulating the garage door but not the garage walls leave a significant hole in your insulation.

Insulating garage walls make sense in cold climates. It also makes sense if your region has summer temperatures above 100 F.

How to Insulate a Finished Garage Wall using Injection Foam?

You must check to see if you can make all the closed cavities. A 2X4 drywall stud will typically be 16 inches apart, while a 2X6 drywall stud will often be 24 inches apart. But you shouldn’t presume that in an old house.

A stud finder can help you find the studs. It is best to examine the wall from horizontal and vertical angles.

To strengthen the structure, vertical studs may occasionally be connected by horizontal bridging or firestops. If you don’t have one, you’ll need to add a vapor barrier, or your insulation could get damp from the cold outdoors and start to mold.

The steps are much the same as any blown-in insulation. Although foam offers a Higher R-Value, thus better insulation against the cold outdoors, and, it has a slight vapor barrier characteristic over other insulation.

What is Blown-In Insulation?

The material used to create insulation batts or rolls is the same as that used to create blown-in insulation.

The fact that they are in loose fill form makes a difference. Which are:


This eco-friendly product is manufactured from newspapers, cardboard cartons, etc.

Loose-fill Cellulose has an R-Value of 3.2 – 3.8 per inch.

Cellulose insulation will cover gaps and holes to create an energy-saving thermal blanket to lower heating and cooling costs. The insulation comprises 85% recycled material and offers a Class 1 Fire Rating. (Read Hose Clamp Sizes Chart)

Fiberglass Wool

Loose-fill Glass fibers form fiberglass wool. Loose-fill Fiberglass wool has an R-Value of 2.2 – 2.7 per inch, so a 2X4 wall can attain a 9 – 11 R-Value, which isn’t enough.

You can add as much thickness as needed in attics, which is why it is ideal to be used there.

mineral wool insulation

Mineral Wool

Rockwool is manufactured from blast iron slag. It’s pricey and has 3.3 R-Value per inch.

Even so, it’s a favorite blown-in insulation for garage walls connected to homes thanks to its efficiency and its fire-resistant.

Steps For Insulating Garage Roof

Here are the basic steps you need to insulate your garage ceiling. While there are a few methods, you’ll still need a core set of instructions on installing insulation.

What You Need:

  • Ladders or scaffolding
  • Sharp knife to cut insulation
  • Staple gun to attach facing and vapor barrier to ceiling joists
  • Tape measure
  • Expanding foam

Safety gear includes glasses, long sleeves, long pants, and a face mask. Fiberglass fibers are itchy and irritating.

Installation Steps

It’s simple to install ceiling insulation. You and a friend can benefit from working on this DIY project together. The procedure may be different for matt or roll insulation instead of blown-in insulation.

1. Seal Gaps and Holes

Any gaps and holes in your ceiling that batt or loose fill insulation won’t cover, or fill should be sealed. Also, look for any flaws or gaps in the windows.

For this DIY project, use expanding spray foam insulation. Any vents that promote air circulation under your roof shouldn’t be blocked.

2. Add Ventilation Baffles

To preserve airflow, build baffles or roof vents before adding any insulation to the ceiling. Your roof needs ventilation to keep mildew and moisture buildup at bay.

Garage ceiling insulation could restrict air spaces under the roof, which foam baffles help preserve. Install the baffles close to your roof’s margins, where insulation may collect against the roof.

3. Finished or Unfinished Ceiling?

If the garage ceiling isn’t finished and the joists are visible, you have a few options.

Batt or roll insulation can be put in from the bottom up, and drywall can be used to cover it up.

Using batt insulation or loose-fill insulation is blown in from the top can be done after installing drywall.

You must insulate your garage ceiling from the top if it has already been finished. This entails entering the attic and adding loose fill or insulation as rolls, batts, or both.

The ceiling of an attached garage with a room above may or may not have had insulation added by the builder.

4. Installing Batts Or Rolls

Choose insulation that complements the ceiling joist gaps you have. Standard wall stud and ceiling joist measurements are used to create insulation.

Check your local codes to determine if faced or unfaced insulation is required. A paper or plastic vapor retarder layer is on one side of the faced insulation.

Insulation as batts or rolls is put by forcing it through the ceiling joists. Then, you draw it back down flush to the bottom of the joists. Try to butt the batts’ ends together as closely as you can without kinking the insulation.

You might need to cut the batt to accommodate shorter joists close to walls or corners. To make the batt fit the joist gap, cut it 1 inch wider.

Every 8 to 12 inches, depending on the situation, staple the facing to the sides of the joists. To determine whether this is necessary, check the local codes. (Learn How To Unscrew A Screw Without A Screwdriver)

5. Installing Batts Or Rolls In A Finished Ceiling

When installing a ceiling that has already been finished, the key distinction is that you start at the top. This calls for you to install batts from above in the attic space over your garage.

Avoid stepping on drywall when installing in an attic from the upper side of the ceiling, so grab some 1/2-inch board; foot location is vital, so you need these platforms.

Lay cut batts between the ceiling joists. With faced insulation, the drywall should be placed up against the facing.

Cut spaces open around any wiring and light fittings. All light fixtures, electrical boxes, ductwork, and chimneys should have a 3-inch space around them.

Remember to cut a square foot piece or larger of your fiberglass batts to fit the garage attic door.

6. Install Loose Fill Fiberglass

Instead of batts or rolls, use an insulation blower for loose fill fiberglass or mineral wool.

Fill all cracks and holes with spray foam or caulk.

Baffle any ceiling wiring, pipes, or chimneys, and ensure you make these from drywall or thin metal.

Install scrap wood around your ceiling to gauge insulation depth. Once joists are covered, the depth is unknown. If you don’t want insulation there, install a wall or barrier. Use sheet foam or plywood.

Insulate your ceiling with a blower. Work from the edges inward. Deepen the insulation to make the R-value.

Remember the attic door. Cover the attic door with foam insulation.

Does Insulating A Garage Keep It Cooler?

When you add insulation, it does, help lessen the amount of heat transmission that occurs within your garage walls. It can make a difference even just to insulate the walls or the ceiling.

The months of spring and summer, when it’s warmer outside, and the skies are clearer, are when this will be most helpful. Your garage door can benefit from insulation as well. Insulation will keep your garage cooler and make the living space above more bearable.

How to Insulate a Finished Garage Wall using Blown In Insulation?

Blow-in insulation is much easier to install than injection foam when insulating a finished garage wall. Then, you can carry it out on your own.

You can rent a blower and purchase many bags of cellulose insulation from the nearest home center.

In contrast to injection foam, you only need to drill one hole at the top to install insulation.

The hose and blower disperse blown-in garage insulation. There is one disadvantage when you compare blown-in insulation to injection foam insulation.

While they both match building codes, injection foam offers a superior air barrier compared to blown-in insulation, which has none.

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