Insulating an Attic with Floor Boards: A Step-by-Step Guide

Insulating your attic is a great way to save money on your energy bills and make your home more comfortable year-round. One popular method of insulating an attic is by using floor boards. This method involves laying insulation between the floor joists and then covering it with floor boards.

To begin, you’ll need to measure the space between the floor joists to determine the correct width for the insulation. It’s important to make sure the insulation fits snugly against the floor joists to prevent any air leaks. Once the insulation is in place, you can cover it with floor boards. It’s important to leave a small air gap between the insulation and the floor boards to allow for proper ventilation and prevent moisture buildup.

Table of Contents

Why Insulate Your Attic?

Insulating your attic is one of the most effective ways to improve the energy performance of your home. It helps to reduce energy costs and keep your home comfortable all year round. In this section, we will discuss the benefits of insulating your attic.

Reducing Energy Costs

Insulating your attic can help you save money on your energy bills. The U.S. Department of Energy estimates that you can save up to 20% on your heating and cooling costs by properly insulating your attic. When your attic is not insulated, heat can escape through the roof during the winter, and in the summer, heat can enter your home, making it harder to cool. Insulation helps to keep heat inside during the winter and outside during the summer, reducing the amount of energy needed to heat or cool your home.

See also  Eliminating Attic Mold (Detailed Guide)

Improving Energy Performance

Insulating your attic can also improve the energy performance of your home. The R-value of insulation measures its resistance to heat flow. The higher the R-value, the better the insulation is at resisting heat flow. By increasing the R-value of your attic insulation, you can improve the energy performance of your home, making it more comfortable and efficient.

In addition to reducing energy costs and improving energy performance, insulating your attic can also help to reduce noise levels in your home, prevent moisture damage, and increase the lifespan of your roof.

Overall, insulating your attic is an important step in improving the energy efficiency and comfort of your home. By properly insulating your attic, you can save money on your energy bills, reduce your carbon footprint, and make your home a more comfortable place to live.

Types of Insulation

When it comes to insulating an attic with floorboards, there are several types of insulation to choose from. Each type has its own unique benefits and drawbacks, so it’s important to choose the one that best fits your needs and budget.

Fiberglass Batts

Fiberglass batts are one of the most common types of insulation used in attics. They are made of tiny glass fibers and come in pre-cut lengths and widths to fit between standard attic joists. Fiberglass batts are affordable and easy to install, but they can be itchy and irritating to handle. They also tend to settle over time, reducing their effectiveness.

Loose-Fill Insulation

Loose-fill insulation, also known as blown-in insulation, is made of small particles of fiberglass, cellulose, or mineral wool. It is sprayed or blown into the attic using special equipment. Loose-fill insulation is great for hard-to-reach areas and irregularly shaped attics, and it doesn’t settle over time. However, it can be more expensive than fiberglass batts, and it may require professional installation.

See also  Install a Ceiling Fan Without Existing Wiring and Attic: A Step-by-Step Guide

Rigid Foam

Rigid foam insulation is made of foam panels that are cut to fit between attic joists. It is a great option for attics with exposed rafters or where there is limited headroom. Rigid foam insulation has a high R-value per inch, meaning it provides excellent insulation in a relatively small amount of space. However, it can be more expensive than other types of insulation, and it requires special tools to cut and install.

Spray Foam

Spray foam insulation is a type of polyurethane foam that is sprayed onto the attic floor or walls. It expands to fill gaps and creates an airtight seal that helps prevent air leakage and heat loss. Spray foam insulation has a high R-value and can be used in attics with irregular shapes or hard-to-reach areas. However, it is one of the most expensive types of insulation and requires professional installation.

In conclusion, there are several types of insulation to choose from when insulating an attic with floorboards. Fiberglass batts, loose-fill insulation, rigid foam, and spray foam all have their own unique benefits and drawbacks. It’s important to choose the type that best fits your needs and budget, and to ensure proper installation for maximum effectiveness.

Preparing Your Attic

Before insulating your attic, it’s important to properly prepare the space to ensure maximum effectiveness and efficiency. This can be done by air sealing, ensuring proper ventilation, and addressing any obstructions in the attic space.

Air Sealing

Air sealing is the process of closing gaps and holes in the attic to prevent air leakage. This is important because air leaks can reduce the effectiveness of insulation and cause energy loss. Common areas for air leaks include around chimneys, soffit vents, and recessed lighting. To air seal your attic, follow these steps:

  • Use caulk or foam to seal gaps around chimneys and other openings.
  • Install baffles to prevent insulation from blocking soffit vents.
  • Use spray foam or caulk to seal around recessed lighting and electrical boxes.
See also  How to Clean Your Bluestone Patio: A Step-by-Step Guide


Proper ventilation is important for maintaining a healthy attic environment and preventing moisture buildup. This can be achieved through the use of soffit vents, ridge vents, and rafter vents. To ensure proper ventilation in your attic, follow these steps:

  • Install soffit vents to allow fresh air to enter the attic.
  • Install ridge vents to allow hot air to escape from the attic.
  • Install rafter vents to ensure proper air flow between the insulation and roof deck.


Obstructions in the attic can interfere with the installation of insulation and reduce its effectiveness. Common obstructions include electrical boxes, ductwork, and recessed lighting. To address these obstructions, follow these steps:

  • Install insulation baffles around electrical boxes and other obstructions.
  • Use spray foam or caulk to seal around ductwork and other obstructions.
  • Consider moving recessed lighting fixtures to reduce the risk of fire.

By properly preparing your attic through air sealing, ventilation, and addressing obstructions, you can ensure that your insulation will be as effective as possible.

Insulating Your Attic Floor

Insulating your attic floor can help you save money on your energy bills and keep your home comfortable. Here are some steps to help you insulate your attic floor with ease.

Determining the Amount of Insulation Needed

Before you start insulating your attic floor, you need to determine how much insulation you need. This will depend on the size of your attic and the type of insulation you choose. You can use an insulation calculator to determine the amount of insulation you need.

See also  Cheap and Chic: How to Transform Your Tiny Bathroom on a Tight Budget

Choosing the Right Insulation Type

There are many types of insulation available, including fiberglass batts, blown-in fiberglass, and cellulose. Fiberglass batts are the least expensive option, but they are not the best choice. Blown-in fiberglass is a good option, but cellulose is the best choice. Cellulose is made from recycled materials, and it has a higher R-value than other types of insulation.

Installing Insulation Boards

If you have a finished attic with floorboards, you can install insulation boards. These boards are easy to install and can be cut to fit the size of your attic. You can also use canned spray foam to seal any gaps and cracks.

Installing Insulation Battens

If you have an unfinished attic with a subfloor, you can install insulation battens. These battens are placed between the joists, and they can help to prevent heat loss. You will need to wear protective gear during the installation process, and you will need to make sure that the insulation does not interfere with the structural integrity of your home.

Insulating your attic floor can help you save money on your energy bills and provide additional storage space. It is important to choose the right insulation type and to install it properly to ensure that it is effective. Consider your budget and the size of your attic when choosing the right insulation for your home.

Sealing Air Leaks

One of the most important steps in insulating an attic with floor boards is to seal any air leaks. Air leaks can significantly reduce the effectiveness of insulation and lead to energy waste. Here are some steps to help you identify and seal air leaks in your attic.

See also  Grayscale Kitchen Design Done Right: 9 Gorgeous Color Combos

Identifying Air Leaks

To identify air leaks, start by turning off all sources of ventilation and using a flashlight to inspect the attic for any visible gaps, cracks, or holes. Look for areas where insulation is dirty or disturbed, which can indicate air movement. Check around any penetrations, such as vents, pipes, or wiring, for gaps or holes.

Using Caulk and Tape

Once you have identified the air leaks, use caulk or expanding foam to seal gaps and cracks around windows, doors, and other openings. Use weather-resistant caulk for gaps that are exposed to the elements. Use foam backer rod to fill larger gaps before applying caulk.

For gaps around pipes or wiring, use high-temperature silicone caulk. For gaps around recessed lighting fixtures, use fire-rated caulk. Use weatherstripping around doors and windows to seal gaps.

Use tape to seal any seams or gaps in ductwork. Use foil tape or mastic sealant for ductwork that gets hot, such as around furnaces or water heaters. Use duct sealant for ductwork that stays cool, such as around air conditioning units.


Weatherstripping is an effective way to seal gaps around doors and windows. Use adhesive-backed foam tape or V-strip weatherstripping to seal gaps around doors and windows. Use door sweeps to seal gaps at the bottom of doors.

Other Considerations

When sealing air leaks, be sure to wear a dust mask and gloves to protect yourself from insulation fibers and dust. Check for moisture in the attic and address any leaks or moisture problems before insulating. Consider installing a vapor barrier to prevent moisture from entering the attic.

See also  How to Choose Tiles for Your Living Room (A Comprehensive Guide)

Finally, consider performing a blower-door test to identify any remaining air leaks. This test uses a fan to depressurize the house and identify any leaks. Once you have identified all the air leaks, seal them using the methods described above.

By following these steps, you can effectively seal air leaks in your attic and maximize the effectiveness of your insulation.

Key Takeaways

Insulating an attic floor is a great way to improve energy efficiency in your home. By preventing heat loss, you can save money on your energy bills and reduce your carbon footprint.

When it comes to choosing the right insulation material, cellulose is the best choice, followed by blown-in fiberglass. Fiberglass batts are the least effective option.

Before you start insulating, make sure to seal any air leaks in the ceiling to maximize the effectiveness of the insulation. It’s also important to wear protective gear, such as gloves and a mask, to avoid inhaling insulation fibers.

When laying out the insulation, be sure to cut the product on the ground, not in the attic, to avoid making a mess. Also, make sure that the paper side of the insulation faces downward if you mainly heat your home, and upward if you mainly cool it.

Overall, insulating your attic floor is a relatively easy and cost-effective DIY project that can yield significant benefits. With the right materials and techniques, you can create a more comfortable and energy-efficient home.


Hello! I'm Nikita, the creator of Abodenation, a blog dedicated to home improvement, troubleshooting, advice, and decor. With years of hands-on experience and a keen eye for detail, I love sharing my passion for creating functional, beautiful, and comfortable living spaces with others. Join me on my journey to transform houses into homes, one project at a time.

Articles: 198