Your Ultimate Guide to Spray Foam Insulation

Spray foam insulation - or polyurethane foam - is arguably one of today's most effective thermal insulation materials. This versatile expanding foam is used for many insulation jobs and can fill cavities with an airtight finish, boosting a home’s heat retention. 

Despite its highly impressive performance, spray foam insulation also has its fair share of pros and cons that are important to consider. This ultimate GreenMatch UK guide will walk you through everything you need about spray foam insulation, including costs, applications, grants, and alternatives.

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Polyurethane spray foam is a spray-applied expanding plastic foam that works as an air barrier and excellent thermal insulator. The impermeable nature of this foam filler makes it a great material to seal cracks and gaps, as well as insulate walls, floors, lofts and ceilings against air movement.

When looking at spray foam insulation, you’ll likely come across two main types:

In both cases, polyurethane spray foam is spray-applied by a professional installer using industry equipment. For this reason, it’s important to work with an accredited professional who can conduct the necessary property assessment, prep work, and installation to a high quality.

The cost of spray foam insulation is around £21.5 per m2 (£1.99 per ft2) however can range as far as £50 per m2 (£4.64 per ft2) depending on the density and quality. Overall insulation prices hinge on several factors, such as your home's conditions, accessibility, location, any existing insulation and more. 

Despite the higher cost of spray foam insulation, its durability, longevity, and excellent thermal retention can lead to long-term savings and decades of home comfort. Here’s a breakdown of the average cost range for spray foam insulation, as well as the potential payback period on your investment:

In addition, 100mm thickness foam insulation can bring about massive savings on your energy bills. How much you save depends on your home type and what you are insulating, but we’ve detailed the expected savings per house insulation approach you can expect for a standard 3-bedroom semi-detached home in the UK:

With this considered, spray foam insulation does emerge as a highly effective means of curbing your annual energy costs and improving your home's comfort.

A key point to remember about spray foam insulation is its messy, labour-intensive, and expensive removal process. So much so, that in most cases, spray foam removal costs are far higher than getting spray foam insulation in the first place! 

Some homes may have outdated or damaged spray foam insulation that needs to be removed before adding new insulation. The process takes place by a removal team, who manually cut away the spray foam insulation as close to the original surface as possible without damaging the home's integrity. Then, the rest of the foam is removed by hand. 

Here’s what you could roughly expect to pay for spray foam insulation removal if you live in a standard 3-bedroom semi-detached house:

These costs may fluctuate depending on the complexity of the job, your location and other conditions, but as can be seen, spray foam insulation removal is no cheap task.

Spray foam insulation is highly versatile because of its liquid-expanding form. This way, it can be used to fill in practically any crevices and openings and shape around awkward areas of your home. 

Here are some of the main areas your house can be insulated with using spray foam insulation:

Warm roof insulation is when the underside of your home's roof is insulated to keep your loft area - alongside the rest of your house - temperature-regulated. This approach is most suitable for homes that plan to use their loft area as a living space, not just storage space.

For attic spray foam roof insulation, installers will apply the spray foam to the roof rafters from the underside of your roof for an airtight seal, leading to thermal insulation throughout the rest of your home. The best loft insulation approach will depend on what you want to use your loft for.

Cold loft insulation is when the loft floor is insulated to keep the rest of your house under your loft warm. The choice of how to insulate a loft depends on your needs. This approach is best if you do not plan to use your loft space for living, but just for storage.

For spray foam loft insulation, installers will lift your loft floorboards and apply spray foam in between and over the floor joists before re-attaching the floorboards, providing adequate insulation for the rest of your house.

Similar to loft insulation, underfloor spray foam insulation is done by lifting floorboards, spraying insulation in between and over floor joists, and re-attaching the floorboards. It’s important to note that this form of insulation is only suitable for suspended timber floors, or floors with a cavity space under them.

Solid concrete floors could rather use an alternative insulation approach, such as rigid insulation boards.

Spray foam cavity wall insulation can be applied to new builds before the cavity is sealed, or old builds by drilling entry holes into the cavity space through the outer wall. It’s important to note that foam wall insulation can only be carried out by a professional installer and is not DIY suitable.

An installer will drill small evenly spaced holes from the outer wall to access the cavity space, and inject spray insulation into the cavity with specialised industry equipment. The holes will then be sealed with cement for a seamless finish. This form of wall insulation is mess-free, non-invasive, and takes just a few hours to complete.

You might be wondering; is spray foam insulation good? Spray foam insulation is no doubt one of the most thermally effective insulation materials available on the market today. 

Here are just a few of the key advantages you can experience with spray foam insulation:

Like any insulation material, spray foam insulation has its fair share of cons worth considering. However, by working with a National Insulation Installer that is professional and accredited, rest assured you can avoid most of them.

Regardless, you may have heard plenty of backlash and wondered; why is spray foam insulation bad? Here are some disadvantages of spray foam insulation you should consider when planning to install some:

Most of these problems can be addressed with a professional installer who uses high-quality materials, accounts for ventilation, and carries out high workmanship.

Homeowners around the globe often ask themselves; should I buy a house with spray foam insulation? Let’s look at some of the mortgage problems of this decision.

Spray foam insulation is a double-edged sword. On one end, its robust, durable nature makes it a solid choice once installed, but on the other end, it becomes an absolute nightmare to remove, both financially and labour-wise. This is especially true for poor-quality installations.

As such, many households that have pre-existing spray foam installed may take a negative hit in the housing market. Prospective renters and buyers are reluctant to invest in a house with spray foam, given the inevitable need to one day remove and replace the material.

However, there are some key steps you can take to minimise this risk as much as possible:

While it’s generally advised to avoid spray foam insulation, certain mortgage lenders accept spray foam insulation properties. The Home Owners Association (HOA) claims that certain criteria about the type and condition of spray foam need to be met. 

Most mortgage lenders may even require an inspection of the insulation and make mortgage calculations based on this decision.

With all things considered, spray foam insulation is worth it if you are sure to make the right decisions with your installation. 

Doing everything by the book, working with a professional installer, and paying for high-quality materials can get you a massive return on your investment and 80 - 100 years of home comfort. 

On the other hand, a DIY job, or working with an inexperienced installer can result in painstaking repair costs, significant home damage, and structural issues that plague your home for years to come.

In a bid to become carbon neutral by 2050, the UK government has rolled out two key insulation grants that assist fuel-poor, low-income, and energy-inefficient homes with insulation upgrades, including spray foam insulation.

These schemes are the Great British Insulation Scheme (GBIS) and the Energy Company Obligation (ECO4). Both are active until March 2026 and exist to provide free and reduced-cost insulation upgrades to qualifying households.

Eligibility is generally based on your status as a low-income household. Things such as your council tax bands, your home's Energy Performance Certificate (EPC) rating, and whether you’re a recipient of government benefits are gauged for eligibility.

To learn more about spray foam insulation grants, or the GBIS scheme, you can visit the UK government website directly and fill in the application form. For the ECO4 scheme, you can get into direct contact with your energy supplier to learn more about the application process.

With all things considered, spray foam remains a questionable insulation choice. On one hand, it exhibits some of the best thermal performance of all insulation materials, on the other hand, it’s a very difficult removal process that can potentially damage your home beyond repair. 

For this reason, it’s wise to consider alternatives to spray foam insulation that are safer, more environmentally friendly, and cheaper. Here are some solid competitors worth a thought:

Regardless of the material you choose, the most important step is to work with professional spray foam insulation contractors to make sure the job is done correctly. The best way to land a bargain is to get multiple quotes from installers to find your best fit.

Sadly, not everyone has endless hours for dedicated researching and vetting spray foam insulation companies online, but that's where GreenMatch UK can help you out.

Through our services, you can get 3 free home-tailored quotes from our network of highly qualified installers. No charges or obligations. Simply fill in our 30-second form and let the bargains come to you. Click the button below to begin!