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Should You Insulate Your Garage Ceiling? 6 Easy Steps To Do It Right

If you want to heat or air condition your garage you need to think about insulation first. Heating or cooling will not be efficient with a completely uninsulated garage. Insulating the garage walls and garage door is not enough. You also need to insulate the garage ceiling. Heat rises so a lot of heat goes right through the ceiling and roof. Let’s talk about why and how you should insulate your garage ceiling.

Why should you insulate your garage ceiling.

There are 2 main reasons why you should insulate your garage ceiling.

If you want a heated or air conditioned garage you will need to insulate the ceiling. All the money you spend heating the garage will rise up and go through the ceiling and out the roof. This will leave you with a garage that is still hot and you with less money. This isn’t good. No garage insulation job is complete without the ceiling.

If you have a room above your garage, all the heat from the garage will pass through the ceiling into it. On those hot summer days all the heat from your uninsulated garage is going right up to the room above the garage. This will make it more expensive to air condition your home. If you insulate the garage ceiling, it will prevent the heat from passing into your home.

Improving garage insulation with ceiling, wall insulation, and garage door insulation can help improve your overall home value and will help your garage roof last longer. It can also help with noise control if you happen to enjoy loud activities as well.

insulate garage ceiling

Types of insulation material for ceilings

There are 2 main types of insulation that are commonly use for ceilings. Fiberglass roll or batt insulation and blown in loose fill insulation.

Fiberglass Batts or rolls

The most common type of insulation is fiberglass batt or roll insulation. It is made up of fiberglass fibers in big fluffy rolls or batts. Batts are precut sheets. Rolls are exactly what they sound like. For ceilings it is recommended to use R30 or R38 insulation. The R value is how well it insulates. Thicker insulation has higher R-values. You should use insulation that matches the thickness of your ceiling joists.

Roll or batt insulation can be bare or faced. Faced insulation has a paper barrier on one side. Depending on where you are, local code may require you to use faced insulation. Before starting any project such as this, check your local building codes to see what rules there are.

See this article and table from Johns Manville for a guide on what R-Value insulation to use where you live.

Blown in Loose fill fiberglass or celulose

Blown in insulation is loose fibers or material that is installed with a blower. It is blown into the joist cavities of your ceilings above the drywall or ceiling finish. It can be easier to install in ceilings that are already finished that have tight spaces. Sometimes batts can be difficult to put into small areas in the ceiling. It can’t be used on an unfinished ceiling. There needs to be a surface for the insulation to rest on. Loose fill insulation is commonly made from fiberglass or cellulose. Fiberglass loose fill is similar to the fibers used to make batt or roll insulation. Cellulose insulation is mostly made from recycled paper product.

Spray foam insulation

Spray foam insulation is an expanding spray that can be used to fill gaps and holes as well as walls and ceilings. Like blown in insulation you need to have a finished ceiling to apply it to use it. It can be used along with other insulation types to fill air gaps or holes that can’t easily be filled otherwise. You should use closed cell spray foam so that the foam won’t saturate with water which can lead to mold.

Tools needed for installation

You don’t need a lot of tools to install insulation. The main things you will need are as follows:

  • Ladder or scaffolding to easily reach the ceiling
  • Box cutter knife for cutting insulation
  • Staple gun for attaching facing and vapor barrier to ceiling joists
  • Measuring tape for measuring gaps and lengths
  • Safety glasses, long sleeve shirts, pants, and a dust mask. Fiberglass fibers can be itchy and irritating to the skin and you want to keep them out of your eyes and lungs.

Installation steps for installing garage celing insulation

Ceiling insulation is easy to install. It is a good DIY project for you and a friend. The process can be different for matt or roll insulation from blown in insulation. It is different for finished and unfinished ceilings. Lets take a look at how to install garage ceiling insulation.

1 – Seal gaps and holes with expanding foam

Seal any gaps and holes you find in your ceiling that batt or loose fill insulation won’t fill or cover. Look for window gaps or other holes. Use expanding spray foam insulation for this job. Don’t fill in any vents that are there to help with air circulation under your roof.

2 – Install baffles for ventilation

Before putting any insulation into the ceiling, install baffles or roof vents to maintain ventilation. You need airflow in your roof to prevent moisture build up and mold. Foam baffles help maintain air gaps under the roof and that could be blocked by the insulation.

Install the baffles near the edges of your roof where insulation might bunch up against the roof.

3 – Do you have a finished or unfinished ceiling?

If your garage ceiling isn’t finished and you have exposed joists you have a few options. You can install batt or roll insulation from the bottom and then finish it with drywall. You can install drywall and then use blown in loose fill insulation or batt insulation from the top.

If your garage ceiling is already finished then you will need to insulate it from the top. This means going into the attic and installing batt or roll insulation or blowing in loose fill.

If you have an attached garage with a room above it, the builder may or may not have insulated the ceiling. Never in the history of the world have home builders cut corners. If the garage ceiling is finished and there is a room above with flooring you will have to decide whether you want to rip out the flooring or the garage ceiling to add insulation.

4 – Installing batting or rolls from the bottom

Pick out insulation that works with the joist gaps you have in your ceiling. Insulation is made to fit standard wall studs and ceiling joist dimensions. Look up local codes to see if you need to use faced insulation or unfaced insulation. Faced insulation has a paper or plastic vapor retarder layer on one side.

Batt or roll insulation is installed by pushing it through the ceiling joists. You pull it back down flush to the bottom of the joists. Butt the ends of the batts as close to each other as you can without scrunching up the insulation.

For shorter joists near corners or walls, you may need to cut down the batt to fit. Cut the batt 1 inch wider than the joist gap.

If required staple the facing to the sides of the joists every 8 to 12 inches. Check the local codes to see if this is required.

If you are near an electrical box or light fixture leave clearance. You should leave at least 3 inches around any light fixture. Some local codes will require you to install an insulation baffle around the fixture as well.

For wiring you should cut gaps or slots in the insulation to clear the wiring.

Install a poly vapor barrier on the bottom face of the joists after the insulation if your local code requires it. This will help prevent mold from growing in the ceiling and insulation. Use a 1 joist overlap between sheets of poly vapor barrier. Staple the barrier to the bottom horizontal surface of the joists.

It will look much nicer and the insulation will last longer if you finish the ceiling with drywall or other finishing material. This will cover up the insulation and keep dirt, debris and moisture away from it.

5 – Installing batting or rolls from the top of a finished ceiling

The main difference for an already finished ceiling is that your installing from the top. This means you need to go up in the attic above your garage and lay in batts from above.

If you are installing in an attic from the top side of the ceiling, do not step on drywall. It can’t support your weight. Only step on joists. It is a good idea to get some 1/2 inch plywood sheets to move around that you can stand and sit on.

Cut batts and lay them between ceiling joists. If you use faced insulation, the facing should go down against the drywall.

Cut clearances around any light fixtures and wiring. Leave a 3 inch gap around all light fixtures, electrical boxes, ducting and chimneys. Use a baffle also if required.

Don’t forget to cut a piece of insulation to fit the garage attic door. Why go through the effort to install attic insulation if you leave a big uninsulated door gap in the middle of it.

See the below vide for a guide for installing batt or roll insulation in ceilings.

6 – Installing loose fill fiberglass or cellulose

Instead of laying down batts or rolls you are going to blow in insulation with an insulation blower. You can rent a blower from your local Home Depot or other rental places.

You need to first fill all your gaps and holes with expanding spray foam or caulk. This will keep your insulation from blowing into your garage. You need to build baffles around any electrical, piping or chimneys in your ceiling. You can make these out of spare chunks of drywall or thin sheet metal. Use sheet metal around chimneys and other high temperature items. Seal baffles with caulking.

ceiling chimney with baffle

Install a few pieces of scrap wood around your ceiling so you can judge the depth of your insulation. Once you cover the joists you don’t know how deep it is. If there is anywhere you don’t want insulation to go install a wall or barrier to keep it out of that area. You can use sheet foam or plywood for this.

Use the insulation blower to apply the insulation to your ceiling. Start with the areas along the edges and work back towards the middle. Make the insulation as deep as required for your desired R-Value.

Don’t forget your attic door. For your attic door, use a piece of structural foam insulation to cover the door.

See the below vide for a guide to installing blown in insulation in your ceiling.

Keeping your garage warmer or cooler

For more tips on heating and cooling an unheated garage see our articles on how to keep your garage warmer and how to keep your garage cooler.

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About the author

My name is Doug Ryan. I am a homeowner and love having get togethers and finding the best things to make spending time at home easier and more fun. We spend a lot of time at home so why shouldn’t we have a great time there?  I decided to start Great Home Gear as a way to share my knowledge and enthusiasm for all things home living with everyone.

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