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spray foam insulation application

Spray Foam Insulation Types & Costs

What is Spray Foam Insulation?

Spray foam insulation is an alternative to more traditional materials like glass or mineral wool, cellulose, expanded polystyrene or sheep’s wool. It is a chemical, liquid foam which is sprayed on and then sets into a solid layer of insulation. While the technique has been around for over 30 years it is becoming increasingly popular in the UK because of its versatility. You can use spray foam insulation on your roof, walls, floor and loft. The foam consists of polyurethane which has been filled with bubbles of gas or air.

There are two types of spray foam insulation to choose from: closed cell spray foam or open cell spray foam.

What are the Benefits of Spray Foam Insulation?


Spray foam insulation can be used for roofs, walls and floors and, because it’s sprayed on as a liquid, it can be easily applied in even the most awkward spaces. Spray foam insulation is also a possible option is your home has difficult to treat cavity walls or solid walls which you aren’t able to insulate externally because of planning restrictions. Common uses include:

  • Roof Renovation and Insulation
  • Internal & External Wall Insulation
  • Cavity Wall insulation
  • Timber & Concrete Ground Floor Insulation
  • Timber Frame Insulation
  • Room in Roof Insulation
  • Barn & Loft Conversions

More Insulation for Less

One of the key benefits of spray foam insulation when compared to other types is that less is required to achieve the same level of insulation. This leaves more space in rooms and lofts for storage. For example, 100mm of spray foam has the same insulating effect as 170mm of loft insulation.

Structural Support

Closed cell spray foam will set into a rigid form which can support and reinforce the structure of your home where cavity walls or the roof may be failing with age. It is also waterproof which could be a real benefit for homes in flood-prone areas.

Which Spray Foam is Best?

Generally, spray foam insulation is quick and simple to install as it has the capability to insulate even the most unusual interiors and structures. However, whether you opt for closed or open cell will depend on your home.

Closed Cell Spray Foam

Closed cell foam will set rigidly and as such is the better insulator of the two types. It is so strong it will actually add extra support to the structure of your home. Because of its dense structure closed cell spray foam will prevent draughts in your home and make it easier to maintain a constant temperature in your home.

However, because it’s a solid structure with no air holes, it will not allow moisture to pass through and the room or loft will need to be well ventilated to prevent condensation or damp.

Open Cell Spray Foam

Open cell foam does not set as rigidly as closed cell so more of it is needed to achieve the same level of insulation. It has a much lighter and more flexible structure which means it can be more easily applied in hard to reach places. It is often used as sound insulation. Unlike closed cell, it allows moisture through so there is less chance of condensation issues.

Open cell is usually cheaper than closed cell but it is very important to have your home assessed by a professional to ensure you are applying the correct type for your situation.

Disadvantages of Spray Foam

Professional Installation Needed

If spray foam is installed poorly (with gaps) it will not insulate as effectively. It’s crucial that you find a professional to perform the job.

Condensation and Damp

Spray foam does not allow moisture to pass through which can lead to condensation and damp problems if the room is not ventilated.


Spray foam is a relatively new option for home insulation and as such no one is sure of the potential health concerns of prolonged exposure to the chemicals or how long the toxins are present in the air after installation.


The spray foam is a fossil-based substance which has a high carbon dioxide content so certainly not a renewable option.


There is not way to make spray foam insulation pretty – it’s sprayed on with lumps and bumps and left to set. There’s no way to decorate over it.

How Much Does Spray Foam Insulation Cost?

Spray foam insulation is more costly than more traditional materials like cellulose or fiberglass. And, unlike other insulation solutions, you can’t apply for an ECO grant from the government to cover the cost of installation. So what kind of cost are you looking at?

The cost of spray foam insulation will be impacted by the size of the area you want to insulate, how thickly you want it applied and the type of foam you choose (open or closed cell).

For a thin layer of spray foam we estimate around £20 per square metre but this can rise to £50 per square metre in thicker applications. Closed cell is more expensive than open cell as it delivers a better level of insulation. The Energy Saving Trust estimates it will cost approximately £300 to insulate the loft in a 3 bedroom, semi-detached house with traditional insulation, but this increases to at least £1,000 (and can be as much as £3,000) when spray foam is used.

Who Can Install Spray Foam Insulation?

Spray foam insulation should always be installed by a professional who has been trained and accredited by the BBA (British Board of Agrément).

Poorly installed spray foam will not only fail to insulate your home effectively, but could also cause problems with damp, structural damage and could even devalue your home. For example, expanding foam could put pressure on the structure of your home. The spray foam itself also needs to be certificated by the BBA or an equivalent body to ensure it complies with Building Regulations. Harmful toxins are also released during installation so proper precautions need to be taken.

Before installation begins the installer will conduct a survey to calculate how well insulated your home is and therefore how thickly the foam needs to be applied. They will also assess condensation risk and suggest measures to prevent this becoming a problem.

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Last Updated: 12th January 2022 There are many different types of central heating...

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