The Downside of Spray Foam Insulation

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Ensuring Proper Ventilation in Your North Devon Home

As the director of SNR Roofing based in North Devon, my main aim is to equip our community with the right information to tackle the common roofing issues they encounter. Insulating our homes has become paramount with the escalating energy prices and unpredictable weather conditions. While the UK government has long been endorsing insulation to curtail energy bills and augment the comfort of our homes, it’s crucial to make an informed choice that doesn’t backfire. One such choice is the application of spray foam insulation between the rafters of your roof space. This method, though beneficial in some aspects, may lead to unforeseen problems if not done correctly.

Spray foam is a concoction of isocyanate and polyol resin, which upon application, expands to create a waterproof and airtight barrier. This seems like a brilliant solution, especially when the Energy Saving Trust approximates a saving of up to £300 per year for the average UK home through insulation. When applied correctly, especially with the recommended mineral wool insulation, the benefits are clear. However, when spray foam insulation is used between the rafters, the situation gets a tad complex.

The primary concern arises from the lack of proper ventilation which can lead to condensation, ensuing in a moist environment ripe for mould growth. Unlike mineral wool insulation which is usually placed on the floor of the loft, spray foam is applied directly to the roof rafters. This method may help in balancing the temperature between the loft and the rest of the house, reducing the chances of condensation that occurs when cold air meets warm air. However, it’s not devoid of issues.

A crucial problem is when the spray foam creates an entirely airtight space. While it’s beneficial in keeping the warm air in, it also traps moisture, which can lead to condensation. Therefore, it’s imperative to have ventilation alternatives such as windows, Velux, or vents. Opting for the open-celled variety of spray foam which is more breathable, allowing warm air to escape, could be a viable solution.

Moreover, incorrect application of spray foam insulation could lead to various problems. For instance, an uneven application or inadequate coverage could result in gaps that allow water penetration, culminating in moisture build-up and consequently mould and mildew. Incorrect material mixture could also lead to the foam failing to adhere to the surface, crumbling over time, or in rare cases, emitting harmful fumes.

One grave concern voiced by home surveyors is the potential rotting of roof timbers due to water ingress, which can’t escape through the spray foam, leading to condensation between the spray foam and the underside of the roof slates. Over time, this condensation can saturate the wood trusses and rafters, causing them to rot. A well-maintained roof and a breathable spray foam product can help mitigate this issue.

Additionally, spray foam application to the underside of the roof slates can hinder roof repair efforts as it might become impossible to remove individual slates. A workaround could be spraying onto boards or another barrier material, rather than directly onto the underside of the tiles.

Spray foam insulation has its merits including its longevity, speed of application, and high thermal values. However, the right application is key to reaping these benefits without facing the aforementioned issues.

If you’re considering spray foam insulation, it’s advisable to consult with roofing experts to understand the unique needs of your home. At SNR Roofing, we are dedicated to providing tailored solutions to ensure your North Devon home stays warm, dry, and well-ventilated. Get in touch with us today at 01271 900 029 or via email at to learn more about the suitable insulation methods for your home. Explore our website for more insights on roofing solutions that stand the test of time.

Your home’s roofing system is a long-term investment; making informed decisions today can save you a plethora of troubles down the line

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