Spray foam roof insulation

Spray Foam Roof Insulation: Bullet-Proof Your Home Against the Cold

Did you know that a quarter of heat is lost through the roof in an uninsulated home? That’s a chilling statistic – but not nearly as chilling as the amount of money you would accumulate on your energy bill trying to make up for it!

Spray foam roof insulation not only secures your home against the cold but, can also slash the amount you spend on your energy bills

If you’re weighing-up which kind of foam roof insulation to choose for your home (which is why you’re on this page in the first place, right?), then we have written this post especially for you.

Here you can find out everything you need to know about spray foam roof insulation, so you can make an informed decision about how best to insulate your home.

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What is spray foam roof insulation?

Spray foam roof insulation is multi-purpose insulation that fills the spaces between roof rafters, joists, and rim joists. It forms an insulating air barrier between your loft and the outside world, protecting you and your home against the Three Deadly C’s: convection, conduction, and condensation.

It’s an unfortunate fact: heat energy is continually transferred out the roof of your house via convection and conduction.

Conduction happens when heat is transferred from the hot area of a solid object to the cool area of a solid object by the collisions of particles. This means that heat can be lost through the rafters, walls, and floors of your loft if they are not insulated properly.

Spray foam roof insulation cost minimises the transfer of heat from your loft to the outside world through conduction. It dramatically slows the transfer of heat from your loft’s rafters, walls, joists, and rim joists – which ultimately results in a warmer, cosier home.

But if you think conduction is a force to be reckoned with, wait until you hear about convection. Convection occurs when heat is redistributed from hotter areas (like your loft) to colder areas (like the outside).

This heat transfer happens via air, so if there are any holes or voids in your loft (a common problem – especially in old houses) then it is almost certain that heat loss is occurring in your loft right now as you read this article.

What’s more, convection also draws heat up from the rest of your home and distributes it outside via your roof. This is why it is essential to not only make sure your loft is insulated

Spray foam roof insulation combats convection by creating an air barrier that prevents warm air escaping your house and stops cold air from invading it.

As foam roof insulation expands when it is sprayed, it effectively plugs any holes and voids it is sprayed into. It does not deteriorate or sag over time, which means once your gaps are sealed, they’re sealed for good.

Further, since foam roof insulation is sprayed as a liquid which then expands to become a solid, it can be sprayed anywhere – no matter how unconventional the design of the loft or how awkward the gaps are to reach.

The last risk your house faces without having proper insulation is condensation. If you do not have insulation, or if it has been poorly installed without the guidance of an expert, then condensation may develop in your loft.

Condensation causes wood to rot. Rotting wood is potentially disastrous, as many lofts rely on wooden rafters to maintain the structural integrity of the roof. Rot caused by condensation destabilises wooden structures in your loft – like rafters, trusses, and purlins – which are vital for holding your roof up.

Spray foam roof insulation can prevent the build-up of wood-rotting condensation.

There is a popular misconception that all types of spray foam loft insulation encourage wood rot. This is because people believe it stifles wood and doesn’t allow it to breathe. This isn’t entirely true.

While it is true for closed cell spray foam roof insulation, it is not true for open cell spray foam insulation.

Icynene, for example, is an open cell spray foam roof insulation that allows the wood to breathe. Open cell foam roof insulation is less dense than closed cell foam roof insulation, so it prevents the accumulation of wood-damaging condensation.

In fact, Icynene has a breathability of 0.0049L/sec/m2, which allows all materials in contact with it to breathe naturally– minimising the condensation build-up in your loft.

So there is no need to foam at the mouth: installing open cell spray foam roof insulation won’t stifle the wood in your loft. Fill in your details below to get Free quote for your roof valid for 12 months:

How is spray foam roof insulation installed?

foam roofing

You could DIY spray foam roof insulation and install it without the guidance of a trained expert, but you may encounter problems a specialist would foresee and prevent.

For example, you may miss vital holes and voids an eagle-eyed expert could identify with ease. Handling and measuring the chemicals involved could be tricky and confusing.

Foam roof insulation also expands in volume up to 100 times after it is sprayed, which an inexperienced sprayer may find difficult to control.

Spray foam roof insulation is usually more expensive than other types of insulation. If you are thinking about installing it in your roof, why risk botching the job and wasting the money you spent on it by doing it yourself?

Consider having it installed by professionals who know exactly how to do it.

Before work starts, a surveyor will assess your roof to ensure the work is carried out to a high standard.

The surveyor will first take your requirements into consideration. Then they will check the condition of the roof’s brickwork, timber, felt, floor, and current insulation (if there is any).

They will spy-out any holes that need filling, and will even look for wasp nests, bats nests, or creepy crawlies!

Once the surveyor has assessed the roof, they will pass on the information to a team of professional sprayers. Before they begin, the team will place plastic sheets over your loft, landing, and any of your belongings to stop foam dripping onto them.

If your roof has no felt or membrane (which is common in older houses), the team will also install a membrane prior to spraying.

After everything is set up, the spray foam roof insulation is then sprayed directly onto the membrane.

The good thing about spraying onto a membrane is that it prevents the foam centre glasgow sticking to the tiles of your roof. This avoids any damage occurring to the insulation should you ever want to replace your tiles in the future.

Tada! In just a few simple steps, your new foam roof insulation is installed and ready for business.

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Types of foam roof insulation

There are many types of foam roof insulation out there, each with their own unique properties.

Below we have listed some popular types of spray foam roof insulation. This list is by no means exhaustive, but it will certainly set you off in the right direction towards choosing the best foam roof insulation for your home:

Icynene spray foam:

Icynene is currently the No.1 leading foam roof insulation on the market. It is the only spray foam to be BBA, ETA, and IAB accredited. It is Energy Saving Trust approved and comes with a 25-year manufacturer’s warranty.

What’s more, Icynene is an open cell spray foam roof insulation. This means it allows timber to breathe – preventing wood-rotting condensation.

For those of you who are environmentally conscious, Icynene is water-based, which means it has a low GWP (Global Warming Potential) and 0 ODP (Ozone Depletion Potential).

In fact, Icynene currently has the lowest GWP of any spray foam roof insulation on the market.

If you’re more concerned about your own health, Icynene Contains no CFCs or Harmful chemicals and is non-toxic during and after installation.

Icynene spray foam is fire retardant. This, therefore, acts as a great substance to reducing the rate of flames spreading.

Lastly, if you just want a bit of peace and quiet, Icynene is also an effective sound dampener.

Not only does it have sound-absorbing properties, but its ability to be sprayed into and fill holes renders it an excellent sound barrier – minimising the bothersome sounds of traffic, barking dogs, and noisy chitter chatter.

Now you can see why it is a market leader. This water-blown spray foam roof insulation is quite literally blowing its competitors out of the industry.

Cementitious spray foam:

Cementitious insulation is a cement-based foam roof insulation.

It can be pumped into closed cavities and is non-toxic and non-flammable. One type of cementitious insulation – Air Krete – is water-based and can be sprayed onto the exterior of houses. It does not expand to fill gaps, it is resistant to mould, deters rodents and insects, and is fully recyclable. It also has a high insulation value.

Phenolic foam:

Phenolic insulation is a 90% closed-cell foam roof insulation. It is both water and fire resistant and can resist almost all inorganic acidic erosion, organic solvents and acids.

Unlike Icynene and Air Krete, the main blowing agent used in phenolic foam roof insulation is Pentane, which is a hydrocarbon. It contains no CFCs or HCFCs and has a low GWP and 0 ODP.

Polyisocyanurate foam:

Polyisocyanurate (what a mouthful to say!) is not a spray foam, but it is still a type of foam roof insulation.

It is a foam that forms an insulating core between two “facing elements". The facing elements which encase the foam could be plain or reinforced aluminium foil, fiberglass-reinforced cellulosic felt, all glass facers, or rigid boards.

This kind of foam is used in commercial roofing systems. It is a “thermoset plastic”, which means it chars in fire rather than turning into a liquid, and it is resistant to molten asphalt and common construction adhesives.

It has good thermal insulation properties and helps reduce the risk of condensation build-up.


Polyurethane spray foam roof insulation usually comes in two forms: closed cell and open cell. Closed cell spray foam roof insulation is denser than open cell foam roof insulation.

Closed cell spray foam roof insulation typically has a lower U Value (or higher R Value, if you are from America), whereas open cell foam insulation tends to have a higher U Value/lower R Value.

(If you are confused about the terms “U Value” and “R Value”, keep reading because we will clear this up for you).

Icynene is an example of polyurethane insulation. Polyurethane insulation is commonly used as insulation in roofs, lofts, walls and ceilings. Because it is sprayed, it is an effective insulator as it leaves no seams or joints through which air can infiltrate – or leak out.

It has a high strength to weight ratio and can be sprayed on a wide variety of materials – including steel. It also provides wind uplift resistance in roofing systems – which means it literally helps keep your roof over your head!

However not all polyurethane insulation is built the same. Quality can vary wildly. Make sure to do your research before you decide which type of polyurethane spray foam insulation you install in your loft.


Foam Roof Insulation U Value: U Value or R Value?

When choosing which kind of foam roof insulation to get there are various pros and cons to consider. An insulation’s U Value is one of them.

U Value is the measure of the heat transmission through a building part (such as a roof, wall, window) or an insulation material (such as Icynene). The lower the U Value, the better the insulating property of the material.

R Value is the same thing as U Value. When you hear people talking about R Values and U Values, they are referring to the same thing: how much heat energy is transferred through a material.

The U Value of foam roof insulation can be visualised with the help of a picture:

spray foam roof insulaton u value


As you can see from the picture, an advantage of closed cell spray foam roof insulation is that it has a lower U value than open cell spray foam insulation. This means it has higher insulation properties. Which makes closed-cell perfect for spray foam insulation under metal roofs.

However, because it is denser, it can stifle wood and promote wood-rotting condensation. Closed cell spray foam roof insulation can even affect your ability to sell your house and get a mortgage.

On the other hand, open-cell spray foam roof insulation has a higher U Value, but it allows the wood to breathe. Its open-cell structure allows water vapour to pass through it, helping the prevention of condensation.

An insulating material’s U Value can increase over time. Fiberglass insulation, for example, eventually deteriorates. This increases its U Value, which decreases its insulation capability.

Further, when fibreglass deteriorates, plastic covered glass particles can become airborne and linger in your home.

On the other hand, polyurethane spray foam roof insulation does not sag or settle over time. It never loses its shape.

U Value and the longevity of your insulation are important factors to take into consideration when choosing foam roof insulation for your loft.

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Spray Foam Roof Insulation Good or Bad? 

One of the most common questions people ask when researching what kind of spray foam roof insulation to buy is: “is spray foam roof insulation good or bad?” and "Is there any spray foam insulation roof problems?"

We want you to be able to make an informed decision when it comes to buying the best spray foam roof insulation for your home. To make your decision easier, here is a list of spray foam roof insulation pros and cons:

spray foam roof insulation



Can reduce energy bills by up to 50%

Is an air barrier and insulator

Expands to fill holes and cavities – minimising air infiltration and leakage

Has a low Global Warming Potential and zero Ozone Depletion Potential

Dampens and reduces external noise

Open cell structure minimises condensation – and lets timber breathe

Helps prevent mould

Certain types (like Icynene) are water-blown – so no noxious chemicals are emitted

Can be sprayed in awkward-to-reach places

Can be used in lofts, agricultural buildings, and for commercial purposes


Open cell foam roof insulation has a slightly higher U Value than closed cell spray foam roof insulation

It can be more expensive than other types of insulation

Open cell foam roof insulation cannot be used for external applications (outside buildings)

Expansion of the foam can be difficult to control if done without the guidance of an expert

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How Much Does Spray Foam Roof Insulation Cost?

The price of spray foam roof insulation varies depending on several factors. The main determinants of how much foam roof insulation costs to install are:

  • The size and condition of your loft
  • The type of spray foam you use
  • The thickness of the spray foam

The cost of spray foam roof insulation is usually calculated per square meter. A skilled surveyor will be able to give you an accurate and fair price once they have assessed your loft.

Once they have given you a quote, you will be half-way to feeling warmer – and saving up to 50% your energy bill!

To have a professional surveyor give you a free quote that is valid for 12 months, contact us here or call us on 0800 689 1894.

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Spray Foam Roof Insulation: Bullet-Proof Your Home Against the Cold


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