Spray foam insulation risks outlined by property body in new guide for homeowners

Britons planning to improve the energy efficiency of their homes are being warned to do their research before using spray foam insulation.

The popular form of insulation has been widely used by homeowners for several decades – but if it is improperly installed it can cause problems when they come to sell or get a new mortgage. 

A total of 250,000 households are estimated to have used spray foam insulation in recent years, and some are now facing dire consequences as a result.

Quick fix: Spray polyurethane foam is a type of loft insulation that 250,000 households have used in recent years in a bid to make their home more energy efficient

Incorrect installation can pose a structural risk to houses and cause costly repair bills. For example, the foam may not provide the right ventilation, which could cause roof timbers to rot.

Issues like these are picked up on building surveys, and reported to potential buyers – potentially putting them off purchasing the home. 

Lenders can also be reluctant to provide new mortgages. In November, Britain’s biggest building society, Nationwide, warned it could reject mortgage applications on homes where spray foam insulation had been installed badly.

With the average household’s gas and electricity bill rising to £3,000 from next month, many homeowners will be looking for ways to cut costs by making their homes more energy efficient – of which spray foam insulation is one option.

In response to growing concerns over cowboy firms and bad practices within the sector, the Royal Institution of Chartered Surveyors (Rics) today launched a comprehensive guide to advise Britons about the use of spray foam insulation. 

The guide explains what effects spray foam might have on a property’s roof structure, thermal performance and value, as well as outlining the do’s and don’ts when installing insulation in a home.

Unregulated: If spray foam is not installed correctly or sprayed in an unsuitable roof space - one with leaks or defects, or with a condensation issue - it can lead to rot

Unregulated: If spray foam is not installed correctly or sprayed in an unsuitable roof space – one with leaks or defects, or with a condensation issue – it can lead to rot

Sam Piplica, senior specialist in building standards at Rics, said: ‘We are pleased to present this free consumer guide on spray foam insulation to the public. 

‘Rics’s remit is to serve the public, therefore, the guide’s main focus is to educate and raise public awareness of potential issues surrounding spray foam, so that people can make informed decisions based on research and due diligence.

‘Rics is also part of an industry working group on this issue to help not only our members but the wider industry improve their products and services.’

What do homeowners need to know?

Spray foam, also known as SPF, is a form of insulation material that can be applied to roof spaces, walls and floors. 

It is installed by using a spray gun, which can be advantageous when working with unusual designs and tight spaces.

Although adding spray foam insulation can make a home warmer and reduce energy bills, it can also cause some unwanted side effects.

For example, sealing hot air inside can also seal in moisture and make roof repairs more difficult. 

Many of the UK’s older homes – whilst being poorly insulated – were built to breathe. Badly installed insulation can inhibit this ventilation and result in damp.

Rics also advises homeowners to ensure they prioritise certain other home improvements before considering spray foam insulation.

For example, a property needs to be wind and water tight before spending money on improving its energy performance. Adding insulation to a poorly maintained roof could accelerate the decay of any untreated timber roof structures, Rics says. 

Risks of spray foam insulation 

1) Hidden problems 

Some spray foam insulation can make it difficult to identify problems to the roof because it restricts the view from within the roof space. 

This is because if the timber roof structure is covered with spray foam it cannot be fully seen or inspected.

For example, if there’s a roof leak behind some types of spray foam insulation, a homeowner may not notice it, which in turn can lead to rotting timber.

2) Damp and condensation

Poorly installed insulation can lead to damp and condensation, which can damage parts of a property.

For example, most pitched roofs on houses and bungalows are designed to be ventilated and spray foam is a change to the original design. 

Badly installed insulation can negatively impact ventilation and result in damp and rot

Badly installed insulation can negatively impact ventilation and result in damp and rot

A draughty loft above ceiling-level insulation is generally a dry loft. Air circulation balances the moisture vapour to reduce condensation. 

However, spray foam creates a warm roof void. It seals the gaps to prevent draughts and retains heat – but will also seal in moisture unless precautions are taken. 

The Rics advises all homeowners to seek professional advice on how to manage any moisture risks.

3) Energy saving 

There is a risk that installing spray foam insulation won’t have the desired energy-saving effect if it is not done correctly, Rics says.

Although spray foam insulation is a better thermal insulator than the equivalent standard mineral wool loft insulation of the same thickness, existing loft mineral wool insulation can be topped up if needed. 

Doing this can result in a warmer home than if the typical maximum level of spray foam was installed between the roof rafters. 

4) Fire safety  

Homeowners should be aware of the fire risk to their property when using polyurethane spray foam as insulation.

Polyurethane spray foam is typically a flammable material, which will only resist a small flame for a few seconds. 

While unused loft spaces do not require protecting from fire, if a fire does happen, having spray foam will increase the likelihood and extent of damage to the property and any adjoining homes. 

What to consider before installing

1) Don’t accept ‘cold-call’ or unsolicited offers relating to spray foam installations. 

2) Don’t install spray foam insulation in a listed building or other protected building or structure without obtaining listed building consent in advance.

3) Don’t carry out isolated alterations without careful due diligence and planning. 

4) Do get advice from an independent, impartial professional if you are considering alterations or modifications at your property. This means someone who does not have a commercial interest in selling you their product. 

5) Do keep your property in good repair, ensuring it is wind and water tight. 

6) Do consider the whole property before carrying out any alterations. 

7) Do consider how your property is designed to perform – and specifically, understand where ventilation is needed in your property. 

8) Do consider where you spend most time in the building and consider installing more insulation next to your living spaces, for example, at ceiling level in the loft to keep the heat near the rooms you live in. 

9) Do check with your mortgage provider whether its policy allows the installation of such products. 

10) Do check with your insurance provider whether its policy allows the installation of such products with potential increased fire risk.

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