Spray Foam Attic Insulation

How Does Spray Foam Attic Insulation Work?

Attic spray foam insulation is often considered the most effective type of insulation, but how does it actually work? Simply put, spray foam insulation consists of two synthetic materials which, when mixed properly, expand their liquid volume up to 60 times. Spray foam insulation creates a thick layer of powerful thermal insulator, filling all the gaps and cracks in your attic. Because the materials solidify once dry, attic spray foam insulation is completely water-resistant and does not release any particles or allergens into the air. Traditional insulators - like fiberglass - are known to release particles that can cause allergic reactions and respiratory complications.

Spray polyurethane foam insulation is commonly used in one of two ways to insulate your attic space: vented attic and non-vented attic. With a move towards Passive homes, non-vented attics are becoming the obvious choice for enhanced energy efficiency. Non-vented attic insulation is applied directly to the underside of the roof sheathing to insulate the entire attic from exterior temperatures. FOAM-LOK spray foam is installed between the roof rafters, along the soffit areas and directly to all interior surfaces such as gable walls and dormers to produce an air tight building envelope making the attic a part of the conditioned space of the home.


Spray foam insulation is an air barrier material that creates a seal against air movement. Open cell spray foam insulation can expand up to 100 times its original size to fill every nook and cranny in the cavity.

Spray foam insulation’s main ingredients are water-blown and organic chemical compounds derived from petroleum extracts.

  • Environmentally safe.
  • Class one fire rated for the attic and other open cavities in the home.
  • Doesn’t retain water, meaning it doesn’t promote mold and mildew growth if the roof leaks into the attic.
  • Insulates the attic by creating an air seal, helping to lower monthly energy bills.
  • Can create a semi-conditioned space by insulating the roof deck in an unvented attic.
  • Spray foam insulation isn’t a food source for pests that can get into the attic.

Advantages of Spray Foam Attic Insulation

  • Versatile Application

    Attic spray foam insulation has a versatile application method, which gives it a significant advantage over traditional options. It can be applied in narrow areas, blocking gaps and cracks that allow heat transfer.

  • Reduced Energy Consumption

    All types of insulation are designed to stop heat transfer and reduce energy cost, but spray foam insulation can cause the biggest impact in comparison to fiberglass and other types of insulation. An average house can lose up to 40% of its energy through heat loss and air filtration, and since spray foam insulation seals off all gaps, it substantially reduces energy costs.

  • Prevents Air Infiltration

    Air infiltration is bad because it carries heat, but it can also force your house to draw up air from the ground. Homes with poor insulation draw up to 40% of their air from the ground, and if the crawl space is not properly insulated or has no vapor barrier, your crawl space will absorb moisture. This can lead to rot, pest infestations, and mold development among other issues.

  • Stops Vapor and Moisture Transfer

    Your attic can also be affected by high moisture levels, but installing closed-cell spray foam attic insulation will safeguard it from any moisture transfer or damage. Similarly to your crawl space, your attic is prone to harboring pests and developing mold, so keeping moisture levels down is critical to your attic’s well-being.

  • Increases Comfort Levels

    Damp, moist attics are often the source of foul odors and can cause cold floors and other temperature discrepancies. Installing spray foam attic insulation will increase comfort levels for your entire family due to the lack of bad smells, sudden temperature changes, or health risks that may result from moist attics.

  • Durable Insulation

    Spray foam attic insulation is designed to last indefinitely, so it produces fewer used materials or repair costs. Spray foam insulation is dense and will strengthen the structural integrity of your house once it’s applied to your attic walls. Closed-cell insulation is water-resistant as well, so you won’t have to worry about water damage in the winter months.

Why Two Approaches – Vented and Unvented?

Vented attic and roof construction has a long history of successful performance. Why change a good thing?

As the complexity of attic and roof assemblies increases, the difficulty to construct vented assemblies also increases. The more complex a roof geometry, the easier it is to construct the assembly in an unvented conditioned manner. With complex roof designs, multiple dormers, valleys, hips, skylights combined with cathedral construction with interior soffits, trey ceilings, and multiple service penetrations, it is often not practical to construct a vented roof assembly with a FOAM-LOKTM interior air barrier at the ceiling plane. It is more common to locate mechanical systems and duct work in attic spaces.

When such duct work is leaky, significant problems can occur. In high wind regions, particularly in coastal areas, wind-driven rain is a problem with vented roof assemblies. Additionally, during high wind events, vented soffit collapse may lead to building pressurization, window blowout and/or roof loss due to increased pressure in the structure. Unvented roofs (principally due to the robustness of their construction) generally perform better than vented roofs during hurricanes. In coastal areas, salt spray and corrosion are a major concern with steel frames, metal roof trusses, and truss plate connectors in vented attics. Finally, in wildfire zones, unvented roofs and attics have significant benefits in terms of fire safety over vented roof assemblies.

Air Movement Comparison


Lapolla has over 30 years of expertise helping home and building owners cut their energy bills.

Contact us today for a free insulation quote.

Related Resources

What is R Value?

The basic function of insulation is to provide a resistance to the flow of heat. R-Value is the term in which an insulation's thermal resistance is rated. Which also indicates the resistance to the flow of heat.

Metal Building Application

Spray foam insulation are proven to work well in a variety of climates and scenarios.  Licensed property specialists can apply the solutions onto ceilings, floors and walls, and the materials quickly seal a building's envelope.

How Safe is Spray Foam?

Spray Foam material is just as safe as the foam pillows you rest your head on.  As it is also used in clothing, automobiles, and electronic equipment as well as many other daily used items.

Crawl Space Insulation

Crawl spaces are peak entry points where humid summer or cold winter air can disturb a home’s temperature stability.  This especially can cause energy bills to skyrocket during the peak of winter and summer.