What is Spray Foam Roof Insulation?

by | Sep 20, 2022

Read Time: 4 minutes

What is Spray Foam Roof Insulation? | Beginners Guide


If you are researching different insulation types for your roof, spray applied foam insulation is one of your options. In this Beginners Guide, we will answer the following questions:

What is spray foam insulation?

Spray Applied Polyurethane Foam is an insulation type that is made on site to suit the size, shape and technical requirements of your roof, wall or floor material that can be used to insulate new or existing roofs, walls, and floors. It insulates by reducing the amount of heat lost by conduction and creating an air barrier to prevent air movement- either warm air escaping or cold air entering the building. It is the fastest growing insulation material throughout North America and Europe, with growth rates of between 7-10% per year.

What is spray foam made of?

Spray foam is created by combining two liquid materials, (polyols and isocyanates) which react to form a cured foam insulation.

How does spray foam roof insulation work?

Spray foam roof insulation is installed as a liquid and quickly expands to create an air seal in the roof. It seals the roof so that air draughts can’t get in through your structure and warm air can’t leak out. As spray foam is sprayed on site, it can reach small hard-to-reach areas and seal them off. This helps to reduce energy bills.

How is the spray foam applied?

The foam is applied to the roof area by professional contractors using specialist equipment.

What are the two types of spray foam?

Open cell and closed cell. Each type has different thermal and vapour resisting properties and the type you choose will depend on your build type.

Open cell foam is made up of small bubble type cells which are not completely closed, making it more permeable to vapour i.e. vapour (but not air) can pass through it

The bubbles of closed cell foam are almost completely sealed off making it less vapour permeable.

You can read more about the two types of spray foam here

Are open and closed cell spray foam both airtight?

Yes, both closed cell and open cell spray and injection polyurethane foams have been independently tested for airtightness and perform exceptionally well as air barriers with figures are low as 0.028m³/hr.m².

Can vapour get through open and closed cell spray foam insulation?

Open cell – yes, it will absorb and release moisture vapour freely*

Closed cell – Liquid water can’t pass through but very small amounts of vapour can still pass through, albeit a lot less than open cell.

*Note: it is extremely important that ventilation is considered as the same time as you are planning a roof insulation project. You can read more about this in the Other Important Things to Know about Spray Foam Roof Insulation paragraph below.

Which Building Regulations apply to spray foam insulation in the UK?

A roof will only comply with the Building Regulations if it is designed and constructed in accordance with Clause 12.4 of British Standard BS5250


For polyurethane spray foam insulation, this is particularly relevant in roof constructions and the appropriate use of ventilation.

Other Important Things to Know about Spray Foam Roof Insulation

As with any roof insulation material, it is essential that you have a ventilation plan that is appropriate for the type of spray foam that you plan to use (i.e., open or closed cell). Having a suitable method of ventilating your roof and attic will ensure that you protect your roof materials and maximise the energy efficiency of your insulation. You can read more about Insulation and Ventilation here

Need more information?

Contact us for more information about any aspect of spray foam insulation on info@econ-pu.com

Related Articles

You can read more detailed information about spray foam insulation here.

Share this post

Share this post

error: Content is protected !!