Insulating Your Attic Bedroom: A Step-By-Step Guide

Insulating an attic bedroom is a moderately difficult DIY project, but it can bring substantial benefits. The attic is where you can find some of the largest opportunities to save energy in your home. By adding insulation, you can maintain the desired temperature throughout your home much better. Proper insulation will help with the retention of warm air in winter and cool air in summer, lower energy costs, and improve air quality.

There are several types of insulation to choose from, including batts-and-blankets, rigid foam, and loose-fill. The type you choose depends on a number of factors such as attic size, climate, and budget. For example, it's better to insulate your attic floor if you're on a budget or have a large attic.

Choose the right insulation

The type of insulation you choose will depend on several factors, including the size of your attic, the climate, and whether you're working with pre-existing material. The most popular choices are fibreglass batt (blankets) and loose-fill (cellulose or blown-in).

Fibreglass Batt Insulation

Fibreglass batts are affordable, accessible, and proven to work. They are sized to fit perfectly between the standard spacing of the wood framing inside walls and ceilings and have a paper backing that helps block moisture. However, their airborne fibres are not healthy to inhale, so it's important to wear protective gear during installation. When installing fibreglass batts, ensure that you do not compress the material and allow it to overlap the top plate of the exterior wall.

Cotton Batts

Cotton batts are a great eco-friendly alternative to fibreglass, offering a comparable R-value. They are made from recycled denim and do not release harmful fibres, making them easier to install. Cotton batts are also a good choice if you want to soundproof a room.

Rigid Foam Insulation

Rigid foam insulation is made of polyurethane and is sprayed into the open framing of walls and ceilings. It provides a higher R-value and better draft protection than fibreglass and cotton batts, and it can get into small, hard-to-reach areas of an attic. However, it is more expensive, averaging double the price of fibreglass.

Closed-Cell Foam

Closed-cell foam is a denser and more expensive option, but it can strengthen the integrity of a structure and reduce moisture. It is inflexible, so it would need to be cut away if you need to access something in your attic or run new venting.

Loose-Fill Insulation

Loose-fill insulation is an environmentally friendly alternative made from recycled materials such as glass, shredded newsprint, cardboard, or industrial waste. It is popular for those seeking a lower attic insulation cost and is easy to install, but it requires careful planning to protect ceiling fixtures, soffit vents, and ductwork. When installing loose-fill insulation, start from the walls and back up slowly towards the centre of the room or the attic entryway, leaving rafter vents uncovered.

Seal air leaks

Sealing air leaks is an important step in insulating an attic bedroom. Here are some detailed instructions to help you with the process:

Firstly, identify the biggest gaps and holes in your attic, as sealing these will provide the biggest savings. Common areas for air leaks include around windows, wiring holes, pipes, exhaust fans, ducts, recessed lighting, dropped soffits, and furnace flues.

Next, create a walkway plan and determine where you will be insulating. Always start in the furthest corner of the attic to avoid trapping yourself. Cut a 16-inch piece of batt insulation and fold it over. Place this into the bottom of a 13-gallon garbage bag to create a vapor barrier. Now, fold it over the bag and stuff it into the open stud cavity of any dropped soffit vents. Cover this with aluminum flashing and seal it in place by caulking the sides.

Repeat the above steps as needed, and then cover these areas with insulation later. Use caulk to seal around windows, doors, or any other gaps, using fire-blocking caulk or foam sealant. If you have a hatch instead of a door, seal around the stair frame and opening using the same method. For chimneys and flues, apply pre-cut aluminum flashing and seal in place with caulk.

Additionally, use hardware cloth to create a 3-inch safety gap around all light fixtures, and ensure that external soffit vents remain free of any blockage to allow for necessary airflow. By following these steps, you will effectively seal air leaks in your attic bedroom, improving insulation and energy efficiency.

Cut insulation

Cutting the Insulation

Now that you've gathered your tools and materials, it's time to cut the insulation to size.

First, hook your tape measure to the furthest point of your wall joist, then measure lengthwise to the inside point of the other joist to get your first measurement.

Next, you'll want to cut the batt to a size that is one inch less than the centre measurement. For example, if there is a 12-inch gap between the joists, cut the batt to 11 inches.

Use a permanent marker to mark the batt where you'll be cutting. Then, use your hand to compress the insulation and cut out each section with a utility knife or box cutter.

Repeat this process, making sure you're cutting double the amount for the second layer. Continue until you have prepared all your insulation for installation.

Certain types of fiberglass batt are sold with perforated edges, so you can simply tear them off instead of cutting.

Install insulation

The type of insulation you choose will depend on factors such as the size of your attic, the climate, and whether you're working with pre-existing material.

Two of the most popular choices are fibreglass batt (blankets) and loose-fill (cellulose or blown-in).

Fibreglass Batt Insulation

Fibreglass batts are a popular choice for homeowners and professionals alike. They are affordable, accessible, and proven to work. They are also fire-resistant and come pre-cut or in rolls with a vapour barrier made of paper. When installing fibreglass batts, ensure that the vapour barrier faces down and stuff the material tightly between the joists.

Loose-Fill Insulation

Loose-fill insulation is made from a combination of fibreglass, cellulose, and minerals. It is environmentally friendly and cost-effective. When installing loose-fill, dump the material around the attic and rake it until it is level, similar to spreading mulch. Ensure that it covers the tops of the joists.

Rigid Foam Insulation

Another option is rigid foam insulation, which has an R-value ranging from R-5 to R-10 per inch of thickness. This means you can achieve a combined R-value of R-23 to R-31 with only 5-1/2 inches of combined fibreglass and foam insulation. Rigid foam sheeting can be used in combination with batt insulation to maximise headroom while maintaining the required R-value.

Batts-and-Blankets Insulation

Batts-and-blankets insulation is another option, with fibreglass batts being the most common type. They are affordable, accessible, and have a proven track record. They are also sized to fit perfectly between the standard spacing of wood framing inside walls and ceilings. Cotton batts are a great eco-friendly alternative, offering a comparable R-value and better soundproofing capabilities.

Seal Air Leaks

Before installing insulation, it is important to seal any air leaks. Common areas for air leaks include windows, wiring holes, pipes, exhaust fans, ducts, recessed lighting, dropped soffits, and furnace flues. Use caulk or foam sealant to seal gaps, and cover external soffit vents to allow for necessary airflow.

Final Touches

Don't forget to insulate your attic entrance, whether it's a door or a hatch. Pre-cut rigid foam boards can be installed against the attic side of the hatch with adhesive caulk. For attic stairs, you can either install a gasket and self-adhesive weatherstripping or purchase an insulated zippered tent cover.

Final touches

Now that the insulation is installed, it's time to focus on the final touches to ensure your attic bedroom is comfortable and energy-efficient. Here are the key steps to follow:

• Seal Air Leaks: Focus on sealing the biggest gaps first, such as those around windows, wiring holes, pipes, exhaust fans, ducts, recessed lighting, dropped soffits, and furnace flues. Use caulk or foam sealant to close these gaps.
• Attic Entrance Insulation: Don't forget to insulate the attic entrance, whether it's a typical door or a hatch with stairs or a ladder. Use pre-cut rigid foam boards and install them against the attic side of the hatch with adhesive caulk. This will help prevent energy loss and keep your attic bedroom comfortable.
• Insulate Attic Stairs: There are two ways to insulate attic stairs. One method involves removing old weatherstripping, measuring and cutting along the bottom edge of the trim, installing a gasket, applying self-adhesive weatherstripping, and attaching a plywood cover with insulated batt. The other option is to purchase an insulated zippered tent cover that fits over the stairs.
• Ventilation: Ensure that your attic has proper ventilation to prevent moisture buildup and ice dams. Keep external soffit vents clear and install rafter vents if needed to allow air to move behind the insulation, keeping the roof cold while the room stays comfortable.
• Storage Considerations: If you plan to store items in your attic, build a simple platform using wooden boards and oriented strand board. Do not place storage items directly on top of the insulation, as this will compress it and reduce its effectiveness.
• Lighting and Electrical Fixtures: Check for any exposed wiring or uncovered electrical boxes in the attic and ensure they are properly insulated and sealed. Use hardware cloth to create a safety gap around light fixtures to prevent heat buildup.
• Final Checks: Before considering the project complete, review common DIY mistakes to avoid any issues. Ensure you haven't neglected to seal air leaks, restricted airflow, or compress insulation. Verify that you've used the correct materials and installation techniques and that your attic has sufficient ventilation.

Frequently asked questions