Insulating Garage Without Drywall  

A garage is similar to an attic or basement in that it’s a place where insulation is often overlooked entirely – or at least minimized. The good news is if you’re ready to tackle this project, it’s a much easier task if you’ll be insulating a garage without drywall in place yet. You’ll have three options to consider as you prefer to accomplish this task:

  • Blown-in insulation
  • Spray foam insulation
  • Fiberglass batt insulation

Below, we’ll take a look at these three options. You’ll also find some guidance for installing each type of insulation in your garage.

How to Insulate a Garage Without Drywall Using Blown-In Insulation

Blown-in insulation is a type of insulation conveniently “blown” into place with a large hose. Also called loose-fill insulation, it easily fills wall, joist, or stud cavities in a garage. It’s also known for having a good R-value – referring to a measure of the ability to minimize heat/air transfer.

What Blown-In Insulation is Made of

There are many materials that can be used to make blown-in insulation, including Styrofoam pellets and loose fiberglass fibers. The most common material used, however, is cellulose material, which is a blend of recycled newspapers and other wood-based substances. The materials are often treated with chemicals to increase resistance to fire and mold.

How to Apply It without Drywall

Blown-in insulation comes in bags or bales that are tightly packed. A mechanical blower or hopper is used to loosen up the materials and blow the fluffy mixture into the areas of your garage where you want it. These machines can usually be rented from a local home improvement center or hardware store. After you have purchased the right amount of insulation for your walls and the blower is set up you will want to install a fabric barrier onto the wall studs.

You will then want to cut holes in the fabric in the shape of an X. The holes need to be placed half way up the the wall in each cavity. You will then place the hose in the hole facing downward and turn the blower on. Once the insulation reaches the hole you will turn the hose around and fill the top half of the wall cavity.

Cellulose insulation isn’t dangerous health-wise, However, it’s best to use the following items when applying it:

  • A dust mask
  • Safety glasses
  • Gloves

It’s also a good idea to have a helper since more bags will need to be frequently put into the blower so you don’t have to keep stopping and starting. As a general rule, it’s best to slightly overfill your drywall-free garage walls since blown-in insulation settles over time. It’s typically recommended to insulate a garage wall blown-in insulation that has an R-value of at least 30. If this is what you end up going with, according to Home Advisor, you would need 15 bags of blown-in material per 1,000 sq. ft.

How to Insulate a Garage Without Drywall Using Spray Foam Insulation

Also known as spray polyurethane foam (SPF), spray foam insulation is a spray-applied plastic form of insulation. It’s beneficial because it can fill cracks and gaps really well when applied. It’s known for being highly resistant to heat transfer, which can be especially beneficial if your garage tend to be affected by seasonal changes.

What Spray Foam Insulation Is Made of

A soft, low-density material, spray foam insulation is a blend of two ingredients: isocyanate and polyol resin. It also contains a low-conductivity gas that, depending on the specific form used, can provide either increased sound resistance or a higher insulating value.

How to Apply Spray Foam without Drywall

The first step to take with spray foam insulation application is to wear proper protective gear. With spray foam insulation, this includes:

  • A full protective suit
  • A respirator
  • Chemical-resistant gloves
  • Wrap-around goggles

Make sure open walls in your garage are completely dry and free of moisture since spray foam doesn’t adhere well to moist surfaces. Once you get the hose, nozzle, and mix ready, use an empty box or bag to do a test spray. Also, be prepared to spray continuously until you are done with a certain area. If spray foam sits for more than 30 seconds without being sprayed you’ll need to replace the nozzle.

Next, clear the garage of everything so you don’t get spray foam on your car or anything else you want to keep clean. Open the garage door and use fans to ensure proper ventilation and have any ladders you might need set up. With spray foam, it’s best to “picture frame” or spray the perimeter of cavities in your garage walls. Remember that spray foam expands; so a 1/2 inch applied will expand to an inch.

Wait a few minutes after doing the edges to go back and fill in the rest of the cavities in your garage. Also, be careful about how much you apply. One of the most common mistakes with spray foam is applying too much. Each layer of spray foam is called a “lift,” and it’s advised to also wait a few minutes before applying another lift to give it time to cure first. Over-spray can be removed with a knife or curry comb.

How to Insulate a Garage Without Drywall Using Fiberglass Batt Insulation

Often referred to as “the pink stuff,” fiberglass batt insulation is a solid type of insulating material that works well in unfinished walls. It’s appealing because it’s relatively inexpensive and effective when properly installed.

What Is Fiberglass Insulation Made of

Fiberglass insulation is so-named because it’s made of tiny glass particles. The exact mixture will vary by manufacturer, but typically fiberglass batts include silica sand, limestone, and soda ash. It’s also common to add chemicals to increase fire resistance and other desirable qualities.

How to Apply It without Drywall

Because fiberglass particles can irritate skin and cause other potential health issues, remember to wear the right protective gear. With fiberglass insulation application, recommended gear includes:

  • A dust mask
  • Safety goggles
  • Sturdy shoes and a long-sleeved shirt and long pants

Determine how many batts you’ll need by figuring out the area of your garage. Do this by multiplying height and width. Subtract openings such as ones for the garage door, a separate entry door, or any windows you may have in your garage. For the batts you’ll need to cut, use a scrap piece of wood to ensure the cuts are straight. Staple the batts to the sides of studs to make it easier to apply drywall later. Don’t forget to cut pieces for any spaces on the walls adjacent to your garage door. Also, the paper facing should be up against walls since it provides an added barrier.

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