FAQ and Myths

Spray Foam Insulation Frequently Asked Questions

  1. What is spray foam insulation?
    Spray foam insulation is a micro-cellular plastic made from two components, an isocyanate and a polyol-based, resin blend. When mixed together they are applied as a liquid adhesive and expand in place to create an insulation and air barrier system.
  2. What makes it different than traditional insulation like fiberglass?
    For over 50 years, traditional insulation like fiberglass has been measured by one attribute, R-value. Due to the way R-value is tested, it only measures heat transfer by touch, or conduction. On the other hand, spray foam has an impact on all three forms of heat transfer, conduction, convection and radiation.
    Conduction – performance is based on physical R-value
    Convection – spray foam provides an air barrier, reducing heat transfer by air movement
    Radiation – when installed under a radiant surface, such as a hot roof, the interior surface temperature is significantly lowered, thus lowering the radiant heat load
  3. Why should I use spray foam?
    Spray foam insulation creates a new type of building envelope, with the insulation and air barrier on the same plane, changing the way buildings work and offering several key benefits including energy savings, better indoor air quality and improved comfort.
  4. How much does spray foam cost? How much money will I save?
    Spray foam is generally 2.5 to 3 times the cost of traditional fiberglass insulation, with a typical payback period of 3 to 5 years. The life cycle assessment sponsored by SPFA offers detailed analysis of several examples, including both residential and commercial applications.
  5. What is the difference between open-cell and closed-cell foam?
    Both products are spray applied in a similar manner and use the same plural component proportioning equipment. They also both provide insulation and air barrier qualities in a single application. However, the differences are important to understand, especially when deciding which product is best for a specific application. While both products are spray applied, open-cell foam will expand over 100 times its liquid volume, whereas closed-cell foam will expand about 30 to 40 times its volume. This directly impacts the minimum thicknesses of these products, so open-cell foam will typically be sprayed about 2½ to 3 inches minimum and closed-cell foam will be sprayed about 3/4 to 1 inch minimum. On the other hand, there are no maximum per pass thickness limits for open-cell foam but
    closed-cell foam, in general, is limited to approximately 2 to 3 inches per pass, and for greater total thicknesses, additional passes can be sprayed after a cool down period (refer to manufacturer data for limitations on specific products). At the basic level both open-cell and closed-cell foam provide insulation and air barrier qualities in a single application and for interior applications, with little risk of exposure to bulk liquid, the products are interchangeable, and either open-cell or closed-cell can be used. When the application is more complicated or needs additional performance, such as exterior use, low vapor permeance or contact with bulk liquid, then closed-cell foam would be the product of choice to provide additional functionality.
  6. How long has spray foam been around?
    Polyurethane is very common but most people just don’t realize it. You interact with polyurethane every day, the seats and dashboard in your car, your bed, couch, car seats, shoes and more all use polyurethane and in many cases polyurethane foam. In the 60’s polyurethane foam was being used in appliances and furniture in the US and by the 70’s spray foam was being used in building insulation applications. Today, refrigerators, freezers, dishwashers and coolers are all insulated with polyurethane foam. These are all in-plant applications and the spray foam industry has taken all of the necessary equipment from the facility – the generator, compressor, proportioning pump, 200-300 feet of hose and some auxiliary equipment, and put it into the back of a truck to create a mobile factory that can roll out into the field to apply spray foam insulation on-site. This makes spray foam insulation an advanced option that is flexible in use, and can fit any shape, contour or design.
  7. What is spray foam made of?
    Spray foam insulation is type of plastic created from a mixture of two components, an isocyanate and a polyol-based, resin blend. The isocyanate is an industrial adhesive, similar to the adhesive used to make osb, and the resin blend is a mixture of polyols, catalysts, surfactants, fire retardants and blowing agent.
  8. How is spray foam installed?
    Spray foam insulation is spray-applied as a liquid adhesive using specialized plural component proportioning equipment that uses positive displacement pumps and other controls to regulate temperature and pressure of the application. The material is sprayed onto the desired surfaces and expands in place to provide an insulation and air seal.
  9. When is spray foam installed?
    Spray foam insulation is installed after wiring, plumbing and HVAC ducts, but before the gypsum wallboard, typically in the same sequence as other insulation materials, and can be installed in new construction and some retrofit applications.
  10. How long will the installation take?
    Depending on the size & complexity of the building and the available resources of the SPF professional that you work with, the installation time can vary. An average, one-story house, under new construction, can generally be completed in a day.
  11. How long will spray foam last?
    Spray foam insulation is a polyurethane foam, a type of plastic, similar to the foam used in your couch, car seat and bed. As a plastic, spray foam does not sag, settle or deteriorate and is expected to outlast the life of the building.
  12. What are the building code requirements for spray foam?
    Spray foam insulation is regulated by the foam plastic section in both the International Residential Code (IRC) and the International Building Code (IBC). The primary requirements for foam plastics include fire testing in accordance with ASTM E84 and thermal barrier protection that varies depending on how the material is being used.
  13. Does spray foam burn?
    Yes, like most building products, spray foam will burn in the presence of a flame. However, SPF is a thermoset material and will char and flake when burned, it will not melt and drip like a foam coffee cup. Additionally, most commercially available spray foams, intended for use in construction applications, meet Class I fire standards with a flame spread index of less than 25 and a smoke developed index of less than 450.
  14. If it burns, is the smoke dangerous?
    Inhaling smoke results in a lack of oxygen and all smoke is dangerous, spray foam is no different. Breathing in smoke from burning foam is not recommended.
  15. Does spray foam need a thermal barrier or ignition barrier?
    A thermal barrier or ignition barrier may be required depending on the application at hand. In general, spray foam should be separated from the interior of the building by a 15-minute thermal barrier, such as gypsum wall board. Special applications, like attics and crawlspaces, may omit the thermal barrier requirement in lieu of an ignition barrier. Additionally, some spray foam products have completed large scale testing, in accordance with AC 377 Appendix X, and can be installed in attics and crawlspaces without additional protection based on this testing.
  16. Does spray foam need a vapor barrier or a vapor retarder?
    Vapor barrier or vapor retarder requirements vary based on climate zone. As with most building applications, spray foam systems do not require a vapor retarder in southern climates. As the building design moves further north, the need for vapor retarders and vapor barriers increases. Note, closed-cell foam can perform as a low vapor permeance material and in many cases will be sufficient as the insulation, air barrier and vapor retarder, when a vapor retarder is necessary.
  17. What R-value do I need?
    R-value requirements are typically based on local code regulation. In many climates, common R-values are R-13, R-19 and R-21 for walls and R-30, R-38 and R-49 for attics. An appropriate R-value is necessary to get optimal performance from a building envelope, but having an air barrier in direct contact with the insulation, as in the case of spray foam, is even more important than the R-value. Energy analysis can be used to document the projected performance of a residential or commercial project based on various design factors including the insulation, air leakage rates, windows, orientation and HVAC.
  18. Can my building be too tight?
    No, but a building can be under ventilated. The best guidance for the industry is, “Seal it Tight and Ventilate it Right”. Sealing structures and lowering air leakage rates is a key feature of spray foam insulation, but all systems work together and a proper air management system is critical to the operational success of any building. In general, the goal is to seal the structure as tight as possible and take care of the indoor air quality and ventilation with a properly designed HVAC system. The purpose of the design should be to use spray foam in the building envelope to provide optimum thermal efficiency (i.e. Rvalue, low natural air changes and minimal thermal bridging) combined with an HVAC system to manage the interior environment and optimize occupant comfort (i.e. temperature, humidity, indoor air quality) using cost effective methods.
  19. Does spray foam absorb moisture?
    No, spray foam insulation does not wick moisture out of the air. The number one way that moisture migrates is through air movement and by sealing a structure tight, it can be ventilated right and interior relative humidity can be controlled with a proper air management system.
  20. Will spray foam grow mold?
    No, spray foam is a plastic and provides no food value for mold or mildew. Additionally, when a spray foam building envelope is combined with a proper air management system interior relative humidity can be maintained at levels where dust mites and mold cannot grow.
  21. What if my roof leaks?
    As with any building system failure, the problem should be identified and repaired. Depending on your application and the type of foam in use, the identification process and difficulty of repair will vary.
  22. Does spray foam contain formaldehyde?
    No, formaldehyde is not a typical component in today’s commercially available spray foam products.
  23. What substrates can spray foam be used on?
    Spray foam is compatible with and regularly used on many different construction substrates, including wood, metal, concrete and masonry. Note, SPF typically does not adhere well to polyethylene plastic, which is often used as a preparation and masking material.
  24. Can spray foam be installed over electrical wiring?
    Yes, spray foam insulation is compatible with electrical wiring and can be applied directly over it with no concerns.
  25. Is spray foam compatible with cPVC pipes and fittings?
    Yes, industry studies have been conducted showing that SPF and cPVC are compatible.

Spray Foam Myths

Spray Foam Insulation is a very interesting industry.

It has expanded from a small niche market, that was custom home builder centric, and has seemingly exploded to over a billion-dollar industry in a relatively short 15 or so years.

Now, don’t get me wrong, spray foam has been around for more than 15 years, but in the past 15 years it has moved from being focused on the custom residential industry to including a variety of applications:

  • Residential Retrofits
  • Production Builders
  • Light Commercial
  • Large Commercial
  • Industrial, and more

With this meteoric rise and the success of spray foam insulation, there seems to be a never ending list of market assumptions, developments in the building code and design questions. Some of the questions are relevant and important, while others are obviously founded in ignorance.

Let’s take a look at five myths that loom over the spray foam industry and offer some clarification.

Myth #1 – Spray Foam Is New

While manufacturers are constantly developing new formulations, to offer the market more competitive, higher quality products, spray foam insulation is not new.

Actually, modern SPF dates back to the ‘30s, when a German scientist, Dr. Otto Bayer, discovered and received a patent for the fundamental chemical reaction that is the foundation for polyurethane. In the ‘60s, polyurethane foam was commercially available and could be found in appliances, furniture and automobiles.

All we have done is taken what was traditionally an in-plant application and moved all of the equipment into a spray foam rig so we can roll out to a jobsite and create an insulated “cooler” out of your building.

Soon thereafter, another attendee, looking at the side-by-side comparison box, asks, “Closed-cell foam is better than open-cell foam, right?”

Myth #2 – Closed-Cell Foam Is Better Than Open-Cell Foam or Open-Cell Foam Is Better Than Closed-Cell Foam

It’s not as simple as one being better than the other; closed-cell foam is the better choice in some applications and open-cell foam is the better choice in other applications.

Remember, open-cell foam has limitations:

  • It’s not intended for exterior applications
  • It’s not intended to be used in below grade applications
  • It’s not designed for contact with bulk water
  • And, it’s not a Type II vapor retarder

Closed-cell foam is more versatile than open-cell foam, so if any of these are design parameters, then yes, closed-cell foam is not only a better choice, it is the only choice. This means that exterior building envelopes, below-grade basements, wine rooms, pool houses and other applications with significant temperature and relative humidity differences, are all obvious closed-cell foam applications.

On the other hand, when used appropriately, open-cell foam wins the economic analysis every time. Both types of foam are air barriers and when installed at equivalent R-values (i.e. different thicknesses), closed-cell foam can easily cost twice as much as open-cell foam, because the cost per R of closed-cell foam is double that of open-cell foam, with no thermal performance difference.

So, because open-cell foam is more cost effective when installed at equivalent R-values, it’s payback timeframe is much quicker. This means open-cell foam is typically the better choice for interior applications that don’t require the additional physical properties of closed-cell foam; most often this includes interior building envelope applications, like wall cavities and attics, in climate zones 1 through 4.

Next, an attendee comes by and says, “The guys in the booth over there said 3” of their closed cell foam has “effective R-value” of R-38, what’s the effective R-value of your spray foam?”

Myth #3:  Spray Foam Has an “Effective R-Value” That Is Higher Than Its Tested R-Value

No, this is not correct.

Your spray foam insulation does not have a higher “effective R-value” than its tested R-value, stop saying that it does – this is illegal, and gives you and the industry a bad reputation.

R-value is R-value; it is derived and documented based on a tested value, K-factor, and does not magically have a higher resistance than the value listed on its TDS just because you think it is better.

Let me explain…

K-factor is a physical property measured using ASTM C-518 and is important when it comes to optimizing a building’s thermal performance and meeting energy code. K-factor is a material’s thermal conductivity; measured as the amount of heat that passes through a thickness of material per unit area in one hour, if the temperature difference between the hot and cold side of the material is one degree. So the lower the k-factor, the better the thermal performance. To put units to it, it is the number of BTUs that would pass through 1 inch of a spray foam material per square foot, in one hour, if there was a 1-degree Fahrenheit difference between the hot side and the cold side of the foam sample.

While K-factor is the measured value, most of the construction industry works with and refers to R-value.

R-value is thermal resistance and is the inverse, or opposite, of thermal conductivity (K-factor), so the higher the R-value the better the thermal performance. R-value is the amount of heat that is resisted and does NOT pass through a thickness of material per unit area in one hour, if the temperature difference between the hot and cold side of the material is one degree.

When it comes to the building industry and all of this thermal performance business, the problem is that K-factor and R-value only measure one form of thermal transmission, conduction, or heat transfer by touch; these values do not address convection (heat transfer by air movement) or radiation (heat waves).

So, R-value alone does not tell the whole story.

R-value of an insulation can be derated, based on poor application, this is where effective R-value comes into play. All insulations are designed to be installed so that they are in contact with an air barrier on all six sides of the insulation. So, if fiberglass or cellulose is not installed properly, not uniform and has gaps and voids, it can be derated. Meaning its effective R-value would only be a fraction of its tested value.

This is a little different for spray foam insulation, because the insulation is an air barrier. In a stud-wall cavity application, the insulation does not have to contact the inner face of the cavity, because the insulation is already on the same plane as, and is already in contact with, the air barrier because the insulation and the air barrier are the same material.

By providing an air barrier solution, spray foam can reduce a structure’s convection heat transfer load and provide a thermal benefit that is not captured by R-value.

Additionally, spray foam insulation can also have an impact on radiant heat transfer and the associated radiant loads.

Have you wondered why a traditional, vented attic temperature could easily be over 120°F when it is only 90°F outside? This is primarily due to heat radiating off of the superheated roof deck to the inside of the attic.

Under the hot sun, a black shingle roof could easily exceed 150°F surface temperature and as the heat conducts through the roof deck, the interior roof deck surface might be close to 140°F. This heated surface acts like the heating element in your toaster and radiates heat into the attic heating the air up to 120°F.

By installing spray foam insulation to the underside of the roof deck, just like turning off your toaster, you change the temperature of the interior radiant surface. The new radiant surface is the exposed surface of the spray foam and rather than being 140°F, like the exposed roof deck, it will be closer to the interior conditioned temperature, around 80 to 90°F, thus having a tremendous effect on radiant heat transfer.

Overall spray polyurethane foam can address all three forms of heat transfer:

  1. Conduction, of course, with its tested and documented K-factor and R-value
  2. Convection because of its air barrier qualities
  3. And, radiation because the temperature of the exposed radiating surface is significantly lowered.

This is why spray foam outperforms other insulation materials, not because of some magic “effective R-value”, but because spray foam can fundamentally, scientifically, have an impact on all three forms of heat transfer.

Immediately after that, another attendee says, “But if spray foam works so well, can’t you make the house too tight, I mean, doesn’t the house need to breathe?”

Myth #4 – Houses Need to Breathe

No, your house does not need to breathe, it does not have lungs. The people in the house are the ones that need to breathe.

Even if houses needed to breathe, that’s not a very good justification to build leaky, drafty, inefficient buildings.

For energy efficiency and interior comfort purposes, the best approach is to seal the structure as tight as possible, then take care of the indoor air from the inside out, with a proper air management system. After sizing the mechanical system, there are several options for providing fresh air ventilation that range from a simple damper controlled inlet duct that is installed on the return side of the HVAC system, all the way to the high-end energy recovery ventilator, which will condition the supply air using energy from the exhaust air.

The best building science has to offer is, “Build it tight and ventilate right.”

Finally, right before lunch, you get the granddaddy of them all, possibly the biggest, most misunderstood idea when it comes to spray foam insulation, “I love foam, but this stuff is too expensive.”

Myth #5: Spray Foam Is Too Expensive

WOW, this is a shortsighted point of view.

Yes, spray foam is going to cost more than traditional insulation upfront, when installed.

Guess what, a high-performance machine always does!!!

But the standard payback period, for both open-cell and closed-cell foam, in all climate zones, is less than 5 years, that’s more than a 20% ROI.

Where else are you making 20% on your money?

Also, even if the spray foam upgrade costs an additional $10,000, when financed over 30-years, that adds less than $50 to the monthly payment, and with a typical energy savings that can be $100, $200 or more per month, the homeowner is in positive cash flow from day one.

Finally, for you cash buyers, that don’t care about payback, ROI or positive cash flow compared to financing costs, when mechanical systems are properly sized and designed, based on the building envelope package, using spray foam insulation can reduce the size of the mechanical system which means the mechanical system may cost less upfront.

With these concepts in mind, traditional insulation will cost you more in the long run, so if you ask me, it is too expensive not to use spray foam.

The point is that spray foam is the only upgrade that will not only pay for itself, but it can also buy granite counter tops.

Is this possible, while working a simple tradeshow you get questions about five spray foam myths, all before lunch.

It has happened to me; it can happen to you.

Content on this page was provided by Robert Naini, Spray Foam Advisor