A quick fix? – the pros and cons of spray foam insulation

Insulation and heat efficiency are two of the most important aspects of a property, especially with the ongoing climate change issues and the need for the UK government to address it. The beauty of insulation, particularly in older properties, is that it can be added to the structure as and when it is needed.

One of the current weapons used to combat heat retention and loss, and other insulation issues, is spray foam insulation. Also simply called spray foam and spray polyurethane foam (SPF), it’s a liquid foam which is sprayed into position by an applicator, which sets and forms an insulating layer.

Access all areas

Spray foam insulation can be used as a way of insulating all elements of a building, from the roof and loft space, to the walls and floor. Spray foam insulation has been around for about 30 years and like any technology, it has its fans and its detractors. The positives are that it can be used in difficult-to-access areas, and provides the only insulation option in many instances. It can also provide additional sound proofing benefits too and must be installed by a professional – it’s not a DIY ‘quick fix’. Harmful fumes are given off during installation, so specialist equipment and clothing, and if possible open ventilation should be available too. This however isn’t always easy in enclosed roof areas and confined spaces.

One key advantage over conventional loft insulation is its dimensions. Loft spaces are often used for storage and homeowners can lay boards over the joists, to form storage areas. The 270mm thickness of loft insulation required is often higher than the joists’ depth, so you can’t lay boards over the top. But according to the National Insulation Association, spray foam insulation doesn’t need to be that thick – 100mm of spray foam insulation is the equivalent to around 170mm of mineral wool loft insulation – making it a viable option.

Concealing problems

As a result of these specialist installation techniques required, spray foam is more expensive to install than other types of insulation and it can be difficult to remove once in place. It’s a bit like that expanding foam sometimes used by window and door installers, to fill the gaps around newly-installed frames. If you spill any on the fascia brickwork or paths or paving flags, it’s very difficult to remove. It also cannot be decorated over. As a result of creating a sealed space, there’s also the possibility that the roof space ventilation can be compromised, which can then go on to cause humidity and dampness. This is not good for roof spaces and can trigger timber deterioration and rot. It shouldn’t be used in listed buildings, or houses with thatched roofs.

Spray foam insulation can also be sprayed onto the underside of roofs. This can be particularly problematic if there’s a roof leak. Water ingress can be easily detected in normal circumstances – you’ll see a damp patch on the ceiling, or a drip or pool. But if the area is covered and enclosed by foam, you can’t see the problem and the dampness is kept close to the timbers, doing further damage. Wet timbers can later be subject to further problems – such as fungal growth and insect attack. The only way to see what condition the timbers are in, and to treat or replace them, is to remove the sprayed-on insulation foam. If problems like this are left unaddressed, they can become both structurally dangerous and financially costly.

As you can see, spray foam insulation can be the perfect cure, but also cause its own problems. If you’re thinking of installing spray foam insulation in your property, we suggest that you seek specialist advice from one of our experts before starting. We can tell you if the solution is right for you and suggest alternative options if not.