Insulating Your Garage Can Cut Energy Waste—Here’s How to Do It Right

Winterizing anything in your home, whether it's your windows or outdoor faucets, can help protect the rest of your home from damage caused by freezing, and help you save money on your heating bill. If you have an attached garage, insulating it is a great way to immediately improve the energy efficiency of your home by preventing the flow of heat through the attached wall, reducing energy waste. Similarly, if you have a room above the garage, then garage ceiling insulation helps to slow the flow of heat through the ceiling, making the room more comfortable all year round.

However, learning how to insulate a garage door, ceiling, and walls isn’t as easy as simply cutting and pasting some rigid foam boards. You also need to consider proper air sealing and moisture prevention to ensure your ceiling, door, and garage wall insulation installation is a success. Keep reading to find out how to insulate a garage, why it matters, and what the best insulation for a garage is. 

Why Insulating Your Garage Matters

Energy Savings for Attached vs Detached Garages

One of the top reasons to insulate your garage is to improve home efficiency and reduce energy waste. “Insulating your garage door can make your home more sustainable and improve energy efficiency, especially for those who currently use it for additional living space, office space, or a home gym. And because heat rises, second-story rooms built above the garage can also become more comfortable in the summer,” explains Orion Smith, director of systems at Precision Garage Door Service, a Neighborly Company. 

Even if you have a detached garage, insulation will help to keep the garage temperature comfortable for a longer period of time, so that you can minimize the cost of using a space heater or an air conditioner. Though, if you have an attached garage you can reduce energy waste in both the home and the garage by insulating this space. 

Related: 9 Best Winter Garage Maintenance Tips for Homeowners

Temperature Control for Workshops, Home Gyms, and Storage

Controlling the temperature in the garage allows you to make better use of the space, so it is no longer an unbearable sauna in summer or an icebox in winter. “Homeowners with a well-insulated garage door will feel the difference in temperature—anywhere from 10 to 20 degrees warmer or cooler—inside the garage,” says Kara Watkins, senior garage door product manager at Clopay Garage Doors.

By controlling the temperature, you don’t just improve the comfort level of anyone in the garage, you can also provide better storage and care for your tools, electronics, batteries, or gym equipment, reducing the effect of extreme temperature fluctuations. 

Noise Reduction and Moisture Prevention Benefits

Not only will the insulation reduce the flow of heat through the walls, door, and ceiling of the garage, but it will also create a noise reduction barrier. Watkins mentions that you “will hear the difference with an insulated garage. It’s very quiet and the metal on the garage door doesn’t vibrate when it opens and closes.”

Similarly, properly air sealing, moisture sealing, and insulating the garage will have immediate moisture prevention benefits. These layers of protection prevent moisture from building up inside the garage, reducing the risk to any items you have stored within the garage. 

Related: Experts Reveal the Most Durable Garage Floor Coating You Can Buy

Types of Insulation for Garages (Pros & Cons)

Fiberglass Batts 

Fiberglass batts are the most common and budget-friendly option, especially for a DIY installation.

Pros:

• Cost-effective: Generally the cheapest option, making it budget-friendly.
• DIY-friendly: Easy to cut and fit into standard wall studs (stick-built garages).
• Widely available: Found in most home improvement stores.
• Good thermal resistance: Provides decent R-value for heat blocking.
• Non-combustible: Fiberglass itself won't burn, but melts at high temps. 

Cons:

• Poor air sealing: Doesn't block air leaks; needs separate air barrier.
• Moisture issues: Can absorb water, leading to mold, mildew, and reduced effectiveness.
• Irritant: Glass fibers can irritate skin, eyes, and lungs during installation.
• Attracts pests: Can attract rodents if left exposed.
• Sags/compresses: Can lose effectiveness if not installed perfectly or if it settles.

Rigid Foam Board

Rigid foam board insulation is frequently used for garage doors because it’s relatively affordable, moisture-resistant, and versatile. Smith explains that rigid foam board is typically made of “polystyrene (commonly called Styrofoam) and is a lightweight material that’s easy to add to a garage door. It will provide a low level of insulation.”

Pros:

• High R-value: Excellent thermal resistance in a thin profile, great for limited space.
• Moisture resistant: Ideal for humid garages or masonry walls.
• Air barrier: Acts as a good air barrier when joints are sealed, reducing drafts.
• Versatile: Can be cut to fit walls, ceilings, and garage door panels.
• Noise reduction: Helps absorb sound waves. 

Cons:

• Cost: More expensive upfront than fiberglass.
• Installation: Requires careful cutting and sealing of seams; needs a thermal/fire barrier (like drywall) for exposed applications in living spaces.
• Pests: Can be susceptible to insects if not protected.
• Fire hazard: Some types emit toxic fumes when burning, requiring fire covering.

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Spray Foam Insulation

Spray foam insulation is the most costly option for insulating your garage. Smith notes that “polyurethane acts as an expandable spray foam that completely fills the cavity it's injected into. This provides a high level of insulation but comes at an increased cost and cannot be added as a retrofit to an existing garage door.”

Pros:

• Superior air sealing: Expands to fill every crack, creating an airtight barrier.
• High R-value: Offers excellent thermal resistance per inch (R-6 to R-7 for closed-cell).
• Moisture barrier: Closed-cell foam resists water and vapor, great for damp areas.
• Durable & strong: Adds structural stability (closed-cell) and long-lasting performance.
• Sound dampening: Especially open-cell, reduces noise, ideal for workshops. 

Cons:

• High cost: Significantly more expensive than traditional options.
• Professional installation: Requires specialized equipment; DIY is difficult and risky.
• Health/off-gassing: Can release VOCs and odors during curing; needs proper ventilation.
• Environmental impact: Higher carbon footprint than some alternatives.
• Application issues: Improper mixing or over-expansion can cause problems.

Reflective or Radiant Barrier Insulation

Reflective or radiant barriers are great for reflecting radiant heat, making this insulation ideal for pairing with thermal insulation, like fiberglass, since the reflective barriers work best during the summer months and the thermal insulation can help keep the garage warm during the winter months. 

Pros:

• Reflects radiant heat: Stops up to 97 percent of radiant heat from entering in summer, crucial for hot climates.
• Energy savings: Reduces cooling costs significantly in sunny areas.
• Complements other insulation: Works best with thermal insulation (like fiberglass) for year-round benefits.
• Eco-friendly: Many materials are recyclable.

Cons:

• Climate dependent: Less effective in cold climates where heat loss (conduction/convection) is the main issue.
• Requires air space: Must face an air gap (like between rafters) to reflect heat; doesn't stop conduction well.
• Cost & installation: Can be more expensive upfront; proper installation is critical for performance.
• Moisture risk: Can trap moisture if not ventilated, potentially causing mold.

How to Pick the Right Insulation for Your Garage

What to Choose Based on Climate and Garage Use

When selecting an insulation for your garage, you need to consider two main factors: The typical climate in your region and how you intend to use your garage once it is fully insulated. “Insulation is measured in R-value. The simplest way to determine the appropriate level of insulation for your garage is to identify the R-value of insulation materials in your home's exterior walls. For southern climates with mild winters, R-13 is likely plenty. For northern climates with harsher winters, R-21+ is a more suitable option,” says Smith.

Attached garages that you want to use for a workshop, home gym, or even a living space will need insulation with a high R-value to ensure that the space is comfortable. “Detached garages that are only used to park the car or store yard equipment don’t necessarily require high R-value insulated doors, however, some insulation will improve the comfort of the space and durability of the door,” notes Watkins.

By Climate:

• Cold climates: Focus on high R-values (R-13 to R-21+). Materials like closed-cell spray foam, rigid foam boards, and fiberglass batts are great for retaining heat.
• Hot climates: Radiant barriers (reflective foil) are key to bouncing heat away. Insulating the door with foil-backed panels helps significantly.
• Moderate climates: Cost-effective options like polystyrene panels or standard fiberglass work well for basic comfort and energy savings.

By Garage Use:

• Workshop/living space (attached garage): High R-value is crucial. Use spray foam for air sealing or rigid foam/fiberglass in walls/ceilings for stable temperatures.
• Storage/parking (unattached): Lower R-values (R-7 to R-12) might suffice if only protecting items from extreme swings. Reflective barriers are good for heat, but high R-value is better for all-around control.
• Noise reduction: Rigid foam and spray foam also dampen noise from tools or street traffic. 

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What You Need Before You Start Insulating

Tools and Materials Checklist

Don’t start a garage insulation installation without ensuring that you have all the tools and materials that you need:

• 3-mil polyethylene sheeting (for vapor barrier)
• Vapor barrier tape
• Fiberglass insulation batts
• Ladder
• Low-expansion foam insulation
• Staple gun 
• Staples
• Straight edge
• Tape measure
• Utility knife
• Rigid foam board (polystyrene/polyisocyanurate) or pre-cut kits
• Reflective foil insulation
• Double-sided tape
• Marker
• Caulk gun
• Caulking
• Weatherstripping
• Screwdriver (for garage door hinges/struts)

Safety Gear

Beyond the tools and materials you need to get the job done, you should also have proper personal protective equipment to ensure that you are safe while you work:

• Fans (for ventilation)
• Safety gloves
• Safety glasses
• Dust mask or respirator
• Long sleeve shirt 
• Long pants
• Closed-toe shoes

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How to Insulate Garage Walls

Preparing the Wall Cavity

Start by preparing the area. You can remove old drywall (if needed), clear the studs of any nails or debris, lay a drop cloth down on the floors, and cover or remove any furniture. Next, inspect the wall cavity and apply caulk or low-expansion foam to fill any cracks and holes. 

Installing Fiberglass Batts Correctly

Measure the space between the studs. In most cases this will be about 16 to 24 inches. Once you have your measurements, you can cut the fiberglass batts to the correct size with a utility knife, then stuff the fiberglass batts between the studs. If you are using faced insulation, then the paper vapor barrier should point towards the house for an attached garage wall and into the garage for a detached garage wall. Secure the insulation by stapling the insulation’s paper to the side of the studs, not the face of the studs. 

Adding a Vapor Barrier (When Necessary)

If you are using faced insulation, then you will not need a vapor barrier, as this would create a double barrier that would actually trap moisture between it. However, if you are using unfaced insulation then you should unroll the 3-mil polyethylene plastic over the insulation and staple it to the studs. Seal the seams, penetrations (like outlets), and edges using vapor barrier tape to create an airtight seal.

For any windows and doors, simply cover them with the plastic while you are installing the vapor barrier, then cut out the openings after the barrier is in place and use vapor barrier tape to seal the edges. 

Installing Drywall Over Insulated Walls

After installing the insulation and the vapor barrier, you can install drywall over the insulated walls to give the garage a finished look. Measure and cut the drywall, then mount it on the walls, using drywall screws to secure the drywall to the studs. Once the drywall is mounted, use drywall compound on the joints, then apply drywall tape to the seams, before adding more drywall compound over the tape. Allow the drywall compound to dry, then sand it smooth and paint the walls.

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How to Insulate a Garage Ceiling

Insulating Under a Room Above (Attached Garages)

If you have a room above the garage, then insulating the ceiling is a good way to ensure the room remains comfortable all year round. Insulating the ceiling will improve thermal performance, prevent noise, reduce the transfer of odors, and stop drafts from entering the room through the garage. Start by sealing any gaps or cracks, then cut and install fiberglass batts in the gaps between the joists. Put in a vapor barrier and then mount drywall. Alternatively, you can have a pro apply spray foam directly to the garage ceiling to create an airtight seal. 

Installing Insulation Between Joists

Clear the ceiling area by removing any old insulation, then set up a ladder and have a second person nearby to steady the ladder and hand you materials. Measure the gaps between the joists, then cut the fiberglass batts with a utility knife before stuffing the insulation into the gaps. 

If you are using unfaced insulation, then add a vapor barrier over the insulation and secure it with staples. Seal the vapor barrier with vapor barrier tape to ensure an airtight fit. Not all DIYers will add drywall to the ceiling, but if you do, then measure and cut the drywall before mounting it to the ceiling and securing the drywall panels to the joists with drywall screws. Mud, tape, sand, and paint the drywall to finish the job.

Air-Sealing Gaps Around Lighting and Access Panels

Make sure that if there are any lights, pipes, wires, junction boxes, or access panels that you take care to air-seal any gaps or cracks. Use fire-rated caulk or low-expansion foam insulation around the edges of boxes, pipes, wires, access panels, and the join where the garage walls meet the ceiling joists. For non-IC (Insulation Contact) rated recessed lights, build boxes with rigid foam and seal the edges with foam.

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How to Insulate a Garage Door

Garage Door Insulation Kits

When you purchase a garage door insulation kit, it will come with detailed instructions for you to follow. Essentially, you will want to measure the panels on the garage door and potentially loosen the panel screws if your door has horizontal struts so that you can slide the insulation behind them. 

Measure and cut the foam boards to fit inside each panel’s frame, scoring and snapping the foam board for a precise fit. Once the foam boards are ready, slide the insulation in the panel, ensure the finished side faces out into the garage, then tighten the panel screws and secure the foam boards with retention clips. Typically, to use a retention clip, you will slice a small 'X' through the insulation where the clip goes, push the clip through, and snap the front piece to the back piece to hold it firmly. 

Foam Board Cut-To-Fit Method

If you choose to simply install the insulation without a kit, then you can do so with foam board, a utility knife, a tape measure, double-side tape, and reflective foil tape. Measure the garage door panels, then measure and cut the foam boards to fit snuggly within the panel channels. Score and snap the foam boards for clean cuts. 

Apply double-side tape to the panels, then press the foam board insulation firmly onto the door, with the finished side facing out into the garage. Use reflective foil tape to cover all seams and edges for a clean look and to prevent air leaks. 

Weight Considerations and Door Balance

Adding insulation to the garage door will impact the weight and balance of the door. “Garage doors use a counter-balance system to function properly so adding insulation materials directly to the door can upset that balance,” mentions Smith. After installing the insulation, test the garage door’s balance and make adjustments to the springs as needed to ensure that it operates safely, instead of slamming closed or whipping open. 

Related: Most Homeowners Forget This Critical Garage Door Tune-Up. Are You One of Them?

Weatherstripping the Frame and Bottom Seal

The final step of the installation should be adding new doorstop weatherstripping around the perimeter of the garage door, then installing a flexible seal at the bottom of the door to block drafts. If there are any small cracks or gaps remaining in the frame, you can use caulk to seal these openings. 

How to Air-Seal Your Garage for Maximum Efficiency

Sealing Cracks and Gaps Around Windows and Framing

In order to seal the cracks and gaps around the windows and framing you should first remove any old caulk, dirt, or debris so that you have a clean surface to work with. Next, apply a continuous bead of caulk where the window frame meets the wall on both the inside and outside edge, then use a finishing tool or a wet finger to smooth the bead for a tight seal. 

For large gaps between the window frame and rough opening, use low-expansion spray foam, or drill small holes into the frame and inject expanding foam into the shim space. This will fill the gap and create a tight seal between the window and framing. 

Weatherstripping Doors and Threshold Plates

Adding weatherstripping around the perimeter of a door and installing threshold plates creates an effective seal. Measure, cut, and fasten the weatherstripping around the perimeter of the garage door. “Each garage door has a rubber gasket attached to the bottom that presses firmly against the ground to prevent air or water from intruding into the garage, but over time this gasket will wear down (or occasionally be chewed up by rodents) and need replacement,” says Smith.

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Take off the old, worn-out bottom seal from the metal retainer at the door's bottom, then thoroughly clean the bottom edge of the garage door and the garage floor where the seal will sit.  

Slide the new rubber or vinyl seal into the channel on the door's bottom edge and cut the seal to the exact width of the door and trim any excess. Place the threshold seal on the floor, fitting it around the door tracks and apply construction adhesive to the floor along the marked line, then press the seal down firmly, stepping on it to remove air bubbles. Close the garage door, letting it rest on the new threshold for about 24 hours to cure the adhesive.

Insulating Outlets and Switch Boxes

In order to insulate any outlets or switch boxes, start by going to the breaker box and shutting off the electricity to the circuit you are working on. Next, remove the cover plates, then use spray foam or caulk to fill the gaps between the electrical box and the drywall. Seal any openings where wires enter the box using duct seal or putting, ensuring a tight fit around each cable. 

You can also place a pre-cut foam gasket over the outlet or switch and against the wall, lining up the holes, then insert childproof caps into the receptacle holes to block any airflow. Reinstall the cover plates over the pre-cut gaskets.

Moisture & Ventilation Considerations

Preventing Condensation in Humid Climates

When a garage is not properly sealed, insulated, and ventilated, condensation can form on the windows, doors, and any cold surfaces, which will increase the moisture within the garage and may lead to mold and mildew growth. To prevent this from happening, especially in humid climates, it is necessary to install vapor barriers over your insulation and invest in appropriate ventilation, like vents, fans, and dehumidifiers, to control the moisture, create airflow, and manage temperature shifts. 

Related: The Best Dehumidifiers for Basements & Damp Rooms

Adding Ventilation When Insulating a Garage Workshop

There are several ways you can add ventilation to your garage workshop when you are insulating the garage. The most direct method is to install active ventilation, which includes putting in an exhaust fan, a ceiling fan, or installing ridge/eave vents to improve airflow through the garage workshop.

You can also invest in a dedicated dehumidifier to actively remove moisture, especially if you live in a humid climate. Similarly, opening the garage door or windows is a great way to air out stagnant, moist air. Smith suggests that “if you live in a humid climate, consider adding an exhaust vent to your garage door. This will allow humidity to escape a damp garage, preventing the growth of mold or mildew.”

Mold Prevention Tips

Mold and mildew can do significant damage to your insulation and to the structure of the garage if left untreated. Additionally, mold and mildew can negatively impact the air quality within the garage, so it’s important to take steps to prevent mold and mildew. Opt for moisture-resistant materials, like spray foam or rigid foam for the best results, and invest in active ventilation solutions, like fans and vents. 

You should also air seal the garage and install vapor barriers over your insulation to keep the space dry. A dehumidifier will help to pull out any moisture in the air, but you should also avoid leaving piles of organic clutter and refuse, like cardboard, as these materials can contribute to mold growth.

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Cost Breakdown: DIY vs Professional Installation

Material Cost Ranges Per Insulation Type

When you are trying to decide whether to take on a garage insulation project on your own or to hire a pro, it’s good to know what type of costs you will need to shoulder, even for a DIY job. The material costs for the project range widely based on the type of insulation, so while you may find it cost-effective to install fiberglass batts on your own, putting in spray foam insulation without prior experience isn’t recommended. 

• Fiberglass Batt: $0.30 to $1.50 per square foot
• Mineral Wool Batt: $1.40 to $4 per square foot
• Rigid Foam Board: $2 to $4 per square foot
• Open-Cell Spray Foam: $1.60 to $5.50 per square foot
• Closed-Cell Spray Foam: $2.60 to $8.00 per square foot
• Reflective or Radiant Barrier: $0.60 to $2.50 per square foot

When Hiring a Pro Makes Sense 

Generally, an experienced DIYer can handle a garage insulation project if they are working with fiberglass batts, rigid foam boards, and reflective or radiant barrier insulation, simply because these materials are relatively easy to work with and more affordable than spray foam, so if you make a mistake it isn’t as costly to fix it. 

However, if you want to insulate the garage with spray foam or if your garage is large, with high ceilings and many hard-to-reach spots, then it’s highly recommended to call in a professional with the expertise, training, and appropriate tools to handle a difficult garage insulation project. 

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Common Mistakes to Avoid When Insulating a Garage

Blocking Vents or Restricting Airflow

When you are insulating the garage, you want to seal any gaps or cracks around the windows, doors, and in the walls, but you need to be aware of active ventilation sites, like exhaust fans, ridge vents, and eave vents. If you block or restrict the airflow to these ventilation sites, you will trap moisture inside the garage, which can increase the risk of mold, mildew, and rust. 

Overlooking the Garage Door or Ceiling

Many homeowners decide to insulate the garage without considering the garage door or the ceiling of the garage. Watkins says one of the biggest mistakes is “ignoring the garage door. The garage door covers the largest opening on a home. An uninsulated steel garage door easily transfers heat and cold. Some insulation can dramatically improve comfort.” 

Similarly, if you ignore the ceiling of the garage, then heat may escape through the roof. If you have a room above the garage, then this room may experience significant temperature changes throughout the year as the temperatures outdoors change from hot to cold. For this reason, it’s best to insulate the walls, ceiling, and garage door at the same time. 

Forgetting to Air-Seal Before Insulating

While insulating will help to slow the transfer of heat, if you forget to air-seal before you insulate the garage then any gaps or cracks will still allow drafts to enter the garage. This reduces the efficiency of the insulation, allowing heat to seep out of the garage during the winter months, and letting heat seep into the garage during the summer months. Ideally, you should seal gaps around the outlets, windows, doors, and framing before insulating to prevent air leaks. 

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FAQs About Insulating a Garage

What R-Value Should You Use?

The R-value you choose depends on your local climate, as well as where you will be installing the insulation:

For Garage Walls & Ceilings:

• R-13 to R-15: Good for standard 2x4 walls in moderate climates.
• R-19 to R-21: Better for colder climates or if the garage is heated, often achieved with foam board over studs for maximum performance in a 2x4 wall.
• R-30 to R-40: For ceilings in cold climates, depending on joist depth, to stop heat from rising. 

For Garage Doors:

• R-8 to R-12: Sufficient for moderate climates.
• R-14 to R-18: Ideal for regions with more extreme temperatures.
• R-19+: For maximum comfort, especially if the garage is a living space or workshop.

Can You Insulate an Unfinished Garage?

You can absolutely insulate an unfinished garage. In fact, it’s often much easier to insulate an unfinished garage than a finished garage because you don’t need to remove any drywall to access the gaps between the studs. Additionally, you will already have access to any gaps, cracks, or openings that you need to air-seal prior to starting the insulation project. 

Do You Need a Vapor Barrier in a Garage?

It is highly recommended to use a vapor barrier in a garage, unless you are installing faced insulation which already comes with a pre-attached vapor barrier. If you are putting in unfaced insulation, then installing a vapor barrier over the insulation will prevent condensation, mold, and insulation damage.

Will Insulation Make a Garage Warmer in Winter?

Insulating a garage will make a garage warmer in the winter, especially if you have a heat source in the garage, like a space heater. Similarly, if you have an air conditioner in the garage in the summer, the insulation will help to keep the garage cooler.