Expanding Spray Foam Insulation

If you are looking at insulation for your home, there are more choices than blown cellulose and pink fiberglass. Expanding spray foam insulation is increasingly popular due to its many benefits.

Expanding spray foam insulation is made of polyurethane or acrylic latex. The foam has been used in refrigerators and water heaters for many years.

Liquid polyurethane is pressurized and released through spray nozzles. When the spray lands on surfaces it expands and foams up, then hardens to a aerated material. Traditional insulation such as cellulose wool or spun fiberglass leave gaps and voids when applied as ceiling and wall insulation. Expanding spray foam insulation fills out to all cracks and into seams even if they are hidden from view. The sealing ability can practically eliminate air flow and energy transfer.

The resulting expanded polyurethane foam has a high R-value, which is the measure of resistance to energy flow relative to its thickness, when compared to other insulation materials. This high R-value feature can allow 4″ wall construction to achieve the same energy rating as a 6″ wall, providing improved performance at a substantial savings in construction materials and even increased floor area.

Because expanding spray foam insulation is dimensionally stable it does not settle or compress, and maintains its high performance characteristics. It does not absorb or transfer moisture, preventing humidity, condensation, and mold problems. It is also insect and flame resistant.

Although there are retail products for small crack filling tasks, expanding spray foam insulation for large areas is best left to professionally trained contractors who have the necessary equipment and expertise to apply this material effectively and economically.

There are hazardous materials handling issues when the polyurethane is in the liquid and aerosol state that require special precautions. Proper application and cavity filling requires experience and care to achieve the desired outcome and prevent damage or distortion of structural elements by over-expansion.

Coordination with plumbing and electrical installation is critical since the foam insulation encloses these utilities and makes it difficult to change or reinstall.

Expanding foam insulation costs about three times more than traditional materials to install initially. Some of this cost will be offset by savings in other areas and materials as mentioned above. However the longterm payback is increased energy savings year after year, with improved comfort and air quality, that justifies the investment in using expanding spray foam insulation.

22 thoughts on “Expanding Spray Foam Insulation

  1. Pingback: Expanding Foam Wall Insulation | Expanding Foam Insulation

  2. Pingback: Expanding Spray Foam Insulation Installation | Expanding Foam Insulation

  3. admin Post author

    Yes, foamed in insulation works well in crawl spaces. Expanding foam insulation can be sprayed in between the floor joists above and between studs of the walls. Install a vapor barrier over the finished foam to reduce condensation. Consult a professional installer for best results in your particular circumstances and application.

  4. Carol

    I live on the first floor of a condo. The garage is directly below my condo. The floor underneath is cement. There is about a 5 ft. crawl space between the ceiling in the garage and the floor of my condo. I’m thinking about spraying the underneath side of my floor with urethane foam to help insulate it. Will spray foam adhere to the concrete? There is a cold draft between my garage ceiling and the floor of my condo. This results in a very cold floor in the condo.

  5. admin Post author

    Hi Carol,
    Yes, expanding foam insulation adheres to just about any surface.

    Insulation is material to impede conductive energy transfer and is dependent on it’s thickness, and rated by R-value. Foam has a high R-value and can provide excellent insulation with less thickness than other materials.

    If there is a draft there will also be convective losses; therefore, be sure to seal any gaps and cracks that allow air to pass between the spaces. Properly installed spray foam insulation does an excellent job of sealing these gaps and cracks.

    Depending on the temperature difference between the living space and external space, a radiant heat barrier can be also be helpful.

    A qualified contractor should be able to provide a cost benefit analysis.

  6. duane

    We have an addition that was built over a concrete patio. There is about 8″ between the concrete and the bottom over the floor joist’s. The joists have batted insulation between them already. This void is enclosed on 3 sides and a covered deck on the 4th. So there is no chance of rain or snow getting in. Can i use a spray foam to fill the entire void to keep critters out & to help insulate?

  7. admin Post author

    Hi Duane,
    Yes you could but I’m not sure if it would be cost effective to fill the ‘void’. The existing batts, if thick enough, might be adequate, depending on your temperature differential between ground and living space. However, using expanding foam to seal gaps and cracks around the perimeter would be a good plan. Anywhere that you can prevent drafts from disturbing the insulated space adds to efficiency. Sealing gaps with foam and caulking will definitely help keep out critters.

  8. John

    So I have a front concrete stoop with gaps between the foundation and stoop. I have large ants that are traveling into the gaps behind the stoop and would like to seal the gaps. Is there any paintable expanding foam or better yet gray color expanding foam? I have used the yellow stuff before but am hoping there is different colors or paintable formulas. thanks

  9. admin Post author

    Hi John,
    You have an interesting combination of issues! Firstly, I would address the ant problem. If they are large ants such as Carpenter ants, I would treat the area to eliminate them. They may be traveling to wood material in the joists and flooring. Also check for moisture, which ants seek out. Smaller ant species might be nesting in the foundation. Big box stores have several products that can eliminate critter infestations.
    Regarding the concrete stoop; is it stable and secure? Patching cracks can be futile if the concrete is moving around with foot traffic.
    I have used expanding foam to fill and bridge large gaps around a slab foundation. The yellow foam does not stand up well to sunlight so it is prudent to overlay it with caulking and paint. After filling with the expanding foam, cut away excess and sand if necessary to have an even or slightly lower surface. I have had good success with gray concrete caulk, which covers the foam underneath, is flexible, waterproof, and matches the concrete color.

  10. Duane2

    This is a different Duane, but I have a similar installation as Duane who posted on April 22, with the exception that I have 12 inches between the concrete slab and the Subfloor, and there is a 2 inch rigid board as insulation rather than batten insulation. The result is a very cold floor in the colder months.

    If I have foam insulation installed it would completely fill the gap. Should I be concerned with wicking action between the concrete and the insulation?

    Can you identify any installers in Connecticut?

  11. admin Post author

    Hi Duane 2 :),
    A 12″ depth under a floor could add up to a large volume! The rigid foam board is still an effective insulation if it is adequate thickness and well installed with no gaps for convection losses. However, sprayed-in expanding foam insulation is better at creating desired thickness as well as sealing all the gaps between joists and plumbing lines. Since it is waterproof and closed cell you should have no problems with rising damp. Be sure to check out several contractors for expertise and price, and compliance with local codes.
    I’m sorry I don’t have any suggestions for Connecticut installers.

  12. Martin

    I have a townhouse with minimual insulation in the exterior walls. Is it possible to spray the foam in the walls? Will the foam spread into the electrical boxes installed on the exterior walls? Can this be sprayed into an area the will surround the dryer vent?

  13. admin Post author

    Hi Martin,
    Yes, spray foam insulation may be retrofitted into existing walls. With proper installation the electrical boxes will end up surrounded but not filled with foam. The liquid foaming material is injected through a small hole into the wall cavity between studs and expands as it reacts. The insertion hole is then repaired over.
    Be sure to check with your home owners’ association, local building codes, and reputation of any contractors you use.
    See this additional page Expanding Foam Wall Insulation.

  14. Monica

    I am going to be repainting a bedroom in a mobile home. When I remove the strips on the walls there is a gap of about 1/4″. Can I use the foam insulation to fill that gap and then paint it.

  15. admin Post author

    Yes you can paint foam, but it is not very resistant to impact as is. Fill the gaps with foam then cover with something that can take everyday wear and tear.

  16. Laurie

    I’ve been watching various home building and remodeling TV shows and they are saying there are new spray in foams suitable for exterior walls without a vapor barrier, but I cannot figure out which ones these are. Any help on that? I have 6 inch rafters in the celing to insulate. Thank you.

  17. admin Post author

    Hi Laurie,
    I don’t know which specific foams they may be referring to but you can spray expanding foam insulation into rafters while leaving existing roof decking and ceiling wallboard in place, even if there is no vapor barrier already there. That is one of the benefits foam has as retrofit insulation. If there is a bathroom or kitchen in the enclosed space I would be sure to have adequate ventilation, such as an extractor fan to the exterior, to minimize humidity and condensation. Be sure to check local building codes for compliance.

  18. Foam agent

    A foaming agent can be added to concrete mix and mortar. Concrete foam is used as cast-in-place for low cost terrace houses and bungalows construction and in lightweight bricks or blocks for high-rise buildings.

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