Best Air-Sealing Products

You're considering budget insulation like fiberglass batts, but you've heard you should pair it with an air-sealing product. You're hoping to make your insulation more efficient, like spray foam, without paying for spray foam. What products are available to create an airtight seal? Which products should you use for your project?

South Central Services has insulated hundreds of homes with spray foam. While we recommend spray foam insulation for most applications that demand high-performance insulation, we understand that many homeowners are on a tight budget. If you are determined to use budget insulation, it is in your best interest to add an air seal to improve its budget performance.

By the end of this article, you will know the six types of air-sealing products and any brands we recommend.

Why Does Air Sealing Boost Insulation Performance?

Insulation performance is traditionally measured by R-value, or resistance value. R-value gauges the amount of conductive heat transfer a material can prevent. From this perspective, a high R-value means better insulation performance. More heat transfer is resisted with a higher R-value.

However, heat does not only travel by conduction. Heat can also be transferred through convection and radiation. R-value does not measure convective or radiant heat resistance, even though heat can travel through both methods.

An airtight seal slows and stops these other types of heat transfer. When air leakage is prevented, an exchange of air is halted. Any time air leaves, different air is replacing it. Heat travels through that air leakage. In the wintertime, the heat you pay for exchanges with the frigid air outside. During summer, your expensive conditioned air swaps with the summer heat.

Budget insulation products do not stop all methods of heat transfer. Products like fiberglass batts are only measured by R-value. The actual properties of budget insulations cannot create an air seal. You must use other air-sealing products to maximize a budget product's performance and address the different ways heat travels.

For Recessed Lighting: Can Light Covers

Can lights protrude through ceilings. While recessed lighting can be a desirable feature in a home, it presents unique challenges to insulate. Without an airtight seal around can lights, the ceiling offers as much energy efficiency as an open window in the winter.

Can light covers are used for a specific purpose: air sealing around can lights. You cannot repurpose this product for another air-sealing project. However, if you have recessed lighting in your home, can light covers are an excellent investment. By insulating and air sealing around your recessed lighting, you prevent substantial heat transfer through and around the fixture.

For Small Gaps: Silicone Caulking

Caulking is a useful product for new construction and existing homes. Whether a house is new or old, there are lots of tiny gaps that can contribute to energy inefficiency. Sealing off these gaps is critical to boosting your insulation performance.

When our team insulates a new construction home, we use silicone caulking to seal wood-to-wood joists and small gaps around doors and windows. Caulking is also helpful for any gap smaller than a quarter inch.

For Larger Gaps: Professional-Grade Can Foam

Not every gap in a home is tiny. Professional-grade can foam is helpful for gaps bigger than a quarter inch. These could include larger gaps around doors and windows, wire and plumbing penetrations, and larger gaps in the ceiling.

Can foam could be paired with budget insulation like fiberglass to boost its performance. For example, if you were insulating your attic floor with fiberglass batts, air would flow freely between the living space and the attic. Using can foam to outline where the floor studs meet the floor can offer some air sealing. This combination will not compare to spray foam insulation but can improve the budget performance of fiberglass.

The most popular brand of can foam is Great Stuff by DuPont. Great Stuff should be in stock at most hardware stores, though other brands of can foam are available.

For New Homes: Fluid-Applied Air Barriers

When building a new home, the frame is usually wrapped with house wrap. An alternative to house wrap is a fluid-applied air barrier. This product is most commonly used in new construction homes, so it is applied by building contractors. However, this type of product could be used DIY.

These products are for use outside of the home. You would not use a fluid-applied air barrier on your attic floor. While these fluid-applied "house wraps" are a helpful house wrap product, they will not significantly improve the energy performance of fiberglass batts in exterior walls.

For New Homes: Peel-and-Stick Self-Adhesive Membranes

If the idea of a fluid-applied house wrap is too daunting, another option is a peel-and-stick membrane. Rather than trying to control a liquid similar to paint, many companies sell self-adhesive membranes in rolls. This product is also used for new construction homes.

Just like a fluid-applied air barrier, peel-and-stick membranes cannot significantly boost the performance of fiberglass insulation. The combination of budget insulation and these membranes will not match the performance of a premium insulation product.

However, any effort to create an airtight seal can improve energy efficiency. A self-adhesive membrane is a wise investment if you are determined to use budget insulation for a new construction home.

For New and Existing Homes: Spray Foam Insulation

Both types of spray foam insulation can create an airtight seal. Spray foam can also be used for any type of air-sealing project. You can have spray foam installed whether you're building a new house or renovating an existing home.

For smaller projects, spray foam insulation is less cost-effective than can foam or silicone caulking. While it can technically be used, we recommend these other products for anything less than 100 square feet.

Spray foam insulation is best used for larger projects, creating an airtight seal where the thermal envelope is compromised. These projects include attics, basements, crawl spaces, and exterior walls. All of these areas are part of the thermal envelope of a home. Without an airtight seal, they contribute significantly to energy loss in the home.

The Bottom Line About Air-Sealing Products

Creating an airtight seal is key to improving indoor air quality and maximizing a home's energy efficiency. Without an airtight seal, air leakage can waste your conditioned air and raise your energy costs. Air-sealing products can help to lower energy bills and create a more comfortable home.

It is important to choose the right product based on what area of your home is experiencing air leakage. Homes can have all sorts of cracks and gaps, from recessed can lights in your ceilings to wood-to-wood joists behind your walls.

If you want the best performance possible, opt for spray foam insulation. If you're willing to sacrifice performance to save some money, add an air-sealing product to your budget insulation plans.

Not sure if you’re experiencing air leakage in your home? You may benefit from a home energy audit.