Does A Garage Roof Need To Be Insulated?

There are several situations in which the expense of insulating a garage roof may be worthwhile. It helps keep the garage at a suitable temperature year-round, even in very hot or cold weather, which protects stored belongings from the elements and reduces energy bills. To further improve energy efficiency, insulate the roof of your attached garage to cut down on heat leakage via the walls.

In this article, we’ll look at why insulating garage roofs is so important, how to take local climate into account, and some practical advice for finding the best insulation for your home.

Does A Garage Roof Need To Be Insulated?

Whether or not a garage roof needs to be insulated depends on several factors:

  • Climate: In regions with extreme temperatures (both hot and cold), insulating the garage roof can help maintain a more stable and comfortable temperature inside the garage.
  • Usage: If you use your garage for purposes other than parking cars, such as a workshop, storage space, or a home gym, insulation can make it more comfortable and functional year-round.
  • Attached vs. Detached: Attached garages can benefit from insulation because they share walls with the house, affecting overall home energy efficiency. Detached garages may benefit less unless they are used frequently and for various purposes.
  • Energy Efficiency: Insulating the garage roof can contribute to energy savings by reducing heat loss in winter and heat gain in summer, especially if the garage is connected to your home.
  • Protection of Belongings: Insulation helps protect stored items from extreme temperatures, which can prevent damage to sensitive items like tools, paint, or electronics.

While insulating a garage roof may not be strictly necessary in all cases, it can offer significant benefits in terms of comfort, energy efficiency, and protection of stored items, depending on your climate and how you use the space.

What Is The Best Insulation For A Garage Roof?

The best insulation for a garage roof depends on various factors including your budget, climate, and how you plan to use the garage. Here are some options for insulation for garage roof:

  • Fiberglass Batt Insulation: This is a popular and cost-effective choice. Fiberglass batts are easy to install between rafters and provide good thermal resistance (R-value). They are available in different thicknesses to match your insulation needs.
  • Spray Foam Insulation: Spray foam insulation provides excellent insulation properties and air-sealing capabilities. It can be applied directly to the underside of the roof deck and expands to fill gaps and cracks, providing a tight thermal barrier. However, it tends to be more expensive than other options.
  • Rigid Foam Insulation: Rigid foam boards (such as extruded polystyrene or polyisocyanurate) are another effective option. They offer high R-values per inch of thickness and can be installed between rafters or on the underside of the roof deck. Rigid foam insulation also provides good moisture resistance.
  • Reflective or Radiant Barrier Insulation: Reflective or radiant barriers are typically installed on the underside of the roof rafters. They work by reflecting radiant heat away from the interior of the garage. While they are effective in reducing heat gain, they are less effective in colder climates where insulation with an air barrier is needed.
  • Blown-in Cellulose Insulation: Blown-in cellulose insulation can be a good choice if you have irregularly spaced joists or rafters. It’s made of recycled paper and treated with fire-retardant chemicals. It fills gaps and voids effectively and provides good thermal resistance.

When choosing insulation for your garage roof, consider factors such as insulation effectiveness (R-value), moisture resistance, ease of installation, cost, and whether you need additional features like air sealing. It’s also important to ensure proper ventilation to prevent moisture buildup and maintain the longevity of the roof structure.

How Can Insulate My Garage Roof?

Insulating your garage roof can be done effectively by following these general steps. Depending on the specific type of insulation you choose, the process may vary slightly:

  • Assess the Roof Structure: Determine the type of roof structure you have (rafters, trusses, etc.) and measure the spacing between them. This will help you choose the appropriate insulation material and thickness.
  • Choose Insulation Material: Select the insulation material that best suits your needs and budget (e.g., fibreglass batts, spray foam, rigid foam boards, etc.). Consider the insulation’s R-value (thermal resistance) and its suitability for your climate.
  • Prepare the Garage: Clear out any items that may obstruct access to the roof or interfere with insulation installation. Ensure the area is clean and free of debris.
  • Install Vapor Barrier (if necessary): In colder climates or where moisture control is important, install a vapour barrier on the warm side of the insulation to prevent condensation inside the insulation material.
  • Install Insulation
  1. Fibreglass Batts: Fit the batts snugly between the roof rafters, ensuring they are cut to the correct size to fill the space without gaps.
  2. Spray Foam: Apply spray foam insulation evenly to the underside of the roof deck. Allow it to expand and cure as per the manufacturer’s instructions.
  3. Rigid Foam Boards: Cut the foam boards to fit snugly between rafters or attach them directly to the underside of the roof deck using adhesive or mechanical fasteners.
  4. Reflective or Radiant Barrier: Install the reflective or radiant barrier material with an air gap between the insulation and the barrier.
  5. Air Sealing: Ensure that all gaps, joints, and penetrations are sealed to prevent air leakage, which can reduce the effectiveness of insulation.
  • Finish the Installation: Once the insulation is installed, consider adding additional materials such as drywall or panelling to further enhance the finished appearance and durability of the garage interior.
  • Ventilation: Ensure proper ventilation in the garage to prevent moisture buildup and maintain good air quality. This may involve installing vents or ensuring existing vents are unobstructed.
  • Safety Precautions: Wear appropriate protective gear such as gloves, goggles, and a mask/respirator when handling insulation materials, particularly fibreglass or spray foam.
  • Professional Assistance: If you are unsure about any aspect of insulating your garage roof or if the roof structure is complex, consider consulting a professional insulation contractor for guidance or assistance.

By following these steps carefully and choosing the right insulation for your garage roof, you can effectively improve the comfort, energy efficiency, and usability of your garage space.


There are several advantages to insulating your garage roof that you should consider carefully before making a decision. It can make the garage a more comfortable place to live, work, store, or do other things by controlling the temperature within. Insulation cuts down on heat loss in the winter and heat gain in the summer, which means it can help keep utility expenses down. Additionally, if the garage is attached, it can increase your home’s thermal performance and assist preserve stored objects from excessive temperatures.

Think about the weather, how often you use the garage, the insulation, how it will be installed, and if you need any extra features like air sealing or vapour barriers before you insulate your garage roof. If you want your comfort, energy savings, and property security to be at their best, you need to plan and install it properly. Advice adapted to your unique circumstances can be obtained by talking with insulation experts if you are uncertain about the process.