Closeup photo of a woman holding a magnifying glass with cartoon word balloons around her head the read "spray foam insulation" "pros" and "cons."

If you want to build or retrofit an environmentally friendly dwelling, spray foam is going to come up as one of your options for insulation.

Spray foam insulation is a high-performance product that has extraordinarily good thermal qualities. Like all insulation materials, it reduces greenhouse gas emissions by reducing the HVAC requirements of buildings, including our homes. But like most things in life, it has pros and cons.

Spray foam insulation is lauded as being a green, environmentally-friendly material that can increase the structural strength of wood-frame homes. I know that it is particularly useful in hard-to-access places and will help to keep moisture and allergens out of your home. It also has excellent R-values and, depending on the type installed, it can lower your energy bills substantially.

But most spray foam insulation products are manufactured from polyurethane that contains toxic compounds. This contributes to health risks. Also, while cost-effective in the long term, spray foam insulation has high upfront costs. Installation costs can be particularly high. 

There are different types of spray foam insulation, which is one of the reasons that the great debate between the pros and cons of spray foam insulation is quite complicated. I’m going to highlight some of the issues to help you make up your own mind.

Types Of Spray Foam Insulation

Liquid foam insulation materials are used in various parts of buildings to insulate surfaces and reduce air leakage. Different types may be sprayed or foamed-in-place to insulate open cavities in the structure including attics, crawl spaces, and the wall cavities of new-build homes.

Most are supplied in two parts that, when combined, create a chemical reaction that forms polyurethane spray foam. Generally, the two parts contain:

  1. Methylene diphenyl diisocyanate (monomeric MDI) and polymeric methylene diphenyl diisocyanate (PMDI). (It bears mentioning that isocyanates are toxic.) 
  2. A blend of polyols, catalysts, a blowing agent, flame retardant, and surfactants.

Injection foam is a similar insulation product, but it is only used in the enclosed cavities of existing walls, making it very useful for renovations. The installation process is also different from spray foam insulation.

Some injection foams are three-part resin products that are mixed with a foaming agent and water. A great advantage of this type of foam insulation is that it can be installed in walls with existing fiberglass insulation, without removing the old material.

But there are differences too, particularly in the way spray foam insulation is manufactured. For this article, I’m going to focus on spray foam.

Closed-Cell vs. Open-Cell Spray Foam

There are two types of foam insulation that are applied in place: open-cell and closed-cell. Typically, both are made with polyurethane. These have their own pros and cons, so let’s consider this first off.

Closed-Cell Spray Foam

Closed-cell foam is literally made up of high-density cells that are closed. These cells are filled with a gas that enables the foam to expand and fill all the gaps and spaces around it. When it cures, it becomes rigid, which has the benefit of also making the structure it has been applied to stronger.

In states that are regularly affected by hurricanes, like Florida where I live, closed-cell spray foam insulation in walls provides homeowners with peace of mind that their houses will survive big storms. That’s huge!

Closed-cell insulation also has a much greater R-value than open-cell spray foam, which makes it considerably more energy efficient. Typically, the R-value is R-6 to R-7 per inch. It is also 100% moisture impermeable, so it won’t absorb any moisture. This is potentially a great advantage. But if it’s used for roof insulation, it would probably conceal any leaks, which could be a disadvantage.

As you probably know, the R-value of insulation is its thermal resistance, and it is a measure of how well the material will resist heat flow. It is determined by several factors, including thickness and density, which is why closed-cell spray foam is tops for the R-factor!

Open-Cell Spray Foam

Open-cell foam isn’t as dense, and the cells are filled with air, giving the insulation product a spongy texture. It’s more like the foam you find in a foam mattress. It won’t add strength, but it is an excellent insulator and air sealer, and it creates a very effective sound barrier. So, it has its advantages.

Typically, the R-value of open-cell spray foam is R-3.6 to R-3.9 per inch, which is nearly half that of closed-cell spray foam. But it also has a greater expansion rate. It is cheaper than closed-cell products, too, which are more expensive than most other insulation products.

Many experts believe that open-cell foam insulation is more appropriate for roof insulation than other areas of buildings. Also, the U.S. Department of Energy’s Energy Saver website warns that it should not be used below ground level where it might absorb water.

Photo of the underside of a roof with spray foam insulation applied around the rafters.
Spray foam insulation can be applied to the underside of the roof, where it makes a huge difference in heat gain and loss.

Increasing Popularity Of Spray Foam Insulation

There is no doubt that spray foam insulation continues to increase in popularity.

Spray foam insulation has been an option since the 1950s, but it only really took off in the next century, around 2006 when next-generation polyols were manufactured as a blowing agent for insulation.

Then, in 2017, BASF launched its new generation of eco-friendly spray foam insulation, and it’s been all systems go ever since.

According to market experts at Lucintel, the spray foam insulation market is likely to reach $2.1 billion by 2025, with a ​​compound annual growth rate (CAGR) of 5% in 2020 to 7% in 2025. Their take on the primary reason for this growth is the stringent government regulations that are in place to reduce greenhouse gas emissions and increase energy efficiency for our homes and buildings.

They also say that the emerging trends that are helping to grow the industry include the development of fourth-generation blowing agents and a focus on “green” building insulation. The need for sustainable building practices and increased energy conservation is also important (which should go without saying!).

Top Spray Foam Insulation Companies

According to Lucintel, the five top companies in the spray foam insulation market are:

  1. BASF
  2. Carlisle
  3. FFL Partners
  4. Sun Capital
  5. Huntsman

If you opt for spray foam insulation, these are products you should consider using.

Top Applications & Users

Spray foam insulation is proven in the wall insulation industry, and it’s expected that this sector will continue to grow. The market is also greatest in the residential sector, because homeowners are looking for energy-efficient and eco-friendly insulation solutions.

Is Spray Foam Insulation Energy-Efficient?

As I said earlier, spray foam insulation is lauded for being eco-friendly. Certainly, closed-cell spray foam insulation is considerably more energy-efficient than any other type of insulation. But open-cell spray foam insulation, not so much.

It is true that the use of polyurethane foam for insulation has increased substantially over the past decade, because of its energy efficiency. Polyurethane is one of the most popular thermal insulation materials, and, according to research published in 2019, it has the greatest potential of all types.

Its benefits relate to both economics and energy conservation. But this needs to be balanced against its toxicity and the ironic fact that the isocyanates used to make it harm the environment.

Thankfully, because polyurethane products made with water-based non-isocyanates are a much greener alternative to traditional isocyanates, materials continue to evolve. Nevertheless, there is still a long way to go from conventional products that contain toxic isocyanate to a new benchmark made with potentially safer non-isocyanate polyurethane.

Are There Environmental Issues?

There are, indeed, environmental issues related to spray foam insulation. Some are positive and some are negative. Spray foam insulation is regarded as green, and it has the potential to become even more eco-friendly.

While there are significant challenges, the fact that spray foam insulation products have evolved the way they have is encouraging. From a generic product that incorporated materials responsible for depleting the earth’s ozone layer and contributing to global warming, spray foam insulation has developed into one of the most promising eco-friendly insulation products on earth.

Photo of a huge power plant with trucks parked in front and smokestacks in the background. Spray foam insulation can reduce energy use from such power plants.
Well-insulated homes decrease our dependence on power plants, helping reduce carbon emissions. But spray foam insulation also contains questionable chemicals–so the debate continues.

Ozone Depletion & Global Warming

Historically, one of the most significant environmental issues was the use of chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) as foaming agents.

A research report on the Environmental Considerations of Building Insulation produced by the Pacific West Region of the National Park Service contains invaluable information. An eye-opener is that by 1993, most CFCs had been eliminated from insulation products and replaced with less harmful HCFCs.

As the report states, HCFCs are significantly better than CFCs, but they still cause ozone depletion and contribute to global warming.

According to Energy Saver, most foaming agents used nowadays don’t use CFCs or HCFCs, or other materials that are harmful to the ozone layer of the earth. That’s a relief!

Carcinogenic Issues

Today, what scientists call monomeric MDI and PMDI are commonly used to make spray foam. While there are concerns that the materials could have carcinogenic effects if inhaled, in 1996, the EPA ruled that “carcinogenic potential cannot be determined.” This ruling still stands.

But the cloud of uncertainty has still not evaporated.

In 2011, the EPA launched an action plan to find out more about the toxic effects of MDI and related compounds in and around buildings, including our homes. Specific health issues listed include asthma, lung damage, and “fatal reactions.” Spray polyurethane foam (SPF) is one of several generic products in the MDI and Related Compounds Action Plan.

In a 2012 scientific article found on the Centers for Disease Control and Prevention website, David A. Marlow points out that environmentally friendly doesn’t necessarily mean “safe” for humans.

The hazards of MDI are well documented, but there is still a lot that we don’t know about polyurethane spray foam. The biggest risk appears to be the health risks of those working with it, particularly the people who install spray foam insulation in our homes. 

“The popularity of the product and the number of companies using it demands that there be some scientific background informing its use,” he says.

Another study, published in 2019, analyzed the VOC emissions from three spray insulation products. Two were closed-cell and one an open-cell product. This raised alarm bells about the possibility of carcinogens in raw SPF. But again, there is no proof.

So, this debate within the great spray foam insulation debate continues.

A Breakdown Of The Pros & Cons Of Spray Foam Insulation

There is no doubt that spray foam insulation is a top-class insulating solution. Its R-values are good and its air-sealing properties are excellent. Other insulation types, including blown cellulose and fiberglass, let air escape from our homes. This, in turn, lets unconditioned air creep inside.

The health risks of spray foam insulation are something we shouldn’t ignore, but there are health risks with other forms of insulation, too. For instance, while fiberglass insulation has been used for many decades, the fibers can disintegrate. If people breathe them, they risk lung damage.

Here’s a tabulated list of some of the pros and cons of spray foam insulation.

Pros and Cons of Spray Foam Insulation
AdvantagesDisadvantages
Creates a highly energy efficient thermal envelopeUpfront costs are high and installation is expensive
Extraordinary thermal qualitiesPayback takes 2-4 years
Lower ongoing energy costsNot a DIY product
Improves air quality in your homeComparatively long installation process
Keeps allergens and other airborne contaminants out of your homeInstallation process is potentially messy
Closed-cell foam keeps moisture and mold out of insulated areas of your homeOpen-cell foam absorbs water
Closed-cell foam seals all gaps, even in awkward areasThere are known and suspected health risks
No need for a vapor barrier 
Can last for up to 80 years 

Last Thoughts

Spray foam insulation works really well, especially closed-cell spray foam. It has a huge number of pros along with some cons that should not be ignored.

Ultimately, the type of insulation you choose to use will depend on the application, your budget, and your needs. It is always prudent to get professional advice.

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *