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SOLVED: Spray Foam Roof Insulation Problems And Pitfalls

Spray Foam Roof Insulation Problems And Pitfalls

With energy prices increasing almost on a monthly basis, and the weather giving us all kinds of extremes, insulating our homes has never been more important.

This fact has been recognised by the UK government, who have been promoting insulation for many years in a bid to lower energy bills, and make our homes warmer and more comfortable to relax in.

But what if your choice of insulation actually causes more problems than it solves? Many people have concerns about the spray foam roof insulation problems that it may cause. Is it really an issue or are the advantages outweighing the disadvantages?

The Energy Saving Trust estimates that the average UK home can save as much as £300 per year simply by adding insulation to the loft or roof. In most cases, the recommendations are based on mineral wool insulation to a depth of 270mm on the floor of the loft.

When it comes to spray foam insulation that is applied to the underside of the roof between the rafters, the financial benefits are even more impressive, with the initial outlay recouped within just a few years on average.

It is clear, however, that the right application of insulation in your roof can be beneficial – but perhaps the operative word is the “right application”. It is easy to get it wrong, as the following article reveals…

What Is Spray Foam Insulation?

Spray foam is a liquid mixture of isocyanate and polyol resin that is forced together under pressure. When sprayed onto a surface it adheres and then expands to up to 60 times its original size. The result is a waterproof and airtight barrier to both water entering and loss of warm air from your home.

Spray foam can be used in many applications around the home, but is most commonly used as an insulation product either on the rafters of your roof or inside your interior and exterior walls.

There are two main types of spray foam insulation: closed cell and open cell. The former is a dense material that is perfect for sound insulation, while the latter has larger air pockets, and works well as an insulation material. However open cell does allow more air to pass through, enabling more effective ventilation.

Spray Foam Roof Insulation Problems And Pitfalls

When using spray foam insulation, you can achieve an entirely waterproof and airtight solution, but this can mean that warm air can become trapped in the space.

When Roof Insulation Goes Bad

The main concern that people have when it comes to insulating the roof or loft room is condensation. This is actually more likely to happen if the insulation is applied to the floor of the loft (the most common location of mineral wool insulation).

The reason is that the insulative barrier is between the main rooms of the house and the cold space of the loft. This means that there is a huge imbalance between the two spaces, causing the build up of moisture when the cold air meets the warm air.

In the case of spray foam insulation, it is applied to the roof rafters, balancing the temperature in the loft with the rest of the house. This minimises the issue of cold air meeting warm air. However there are still some issues with spray foam insulation on the roof that can be avoided.

Poor Ventilation Equals Condensation

When using spray foam insulation, you can achieve an entirely waterproof and airtight solution, but this can mean that warm air can become trapped in the space.

For this reason it is important to have ventilation options such as a window, Velux or just vents. You can also choose spray foam that is more breathable, such as the open celled variety, as this will allow the warm air to escape.

You can also prevent humidity in the rest of your home by taking advantage of window openings, trickle vents and air bricks.

Your home will certainly be warmer and more airtight, but this can mean that build up of warm air and steam from showers and cooking can find it hard to escape. It makes sense to air your home regularly.

Spray Foam Roof Insulation Problems And Pitfalls

Spray foam will usually last in excess of thirty years; therefore, any foam that starts to fail before this is likely to have resulting from an incorrect mix of materials

Incorrect Application: 3 Problems It Presents

Almost all of the problems associated with spray foam roof insulation comes down to incorrect application. In other words, the spray has not been used in the right way, or the mixture is not right for the location. This can cause a few problems, including the following:

● The area has not been covered adequately causing gaps or without the required depth. The recommendation is that around 100mm of spray foam is used between the rafters, and that it is spread evenly throughout the entire space. If there are gaps, water may penetrate through, and moisture can quickly build up, leading to mould and mildew. It can also mean that the insulation is not working as well as it could be,
● The mixture of materials is incorrect leading to the foam failing to adhere to the surface or crumbling after a short time. Spray foam will usually last in excess of thirty years; therefore, any foam that starts to fail before this is likely to have resulting from an incorrect mix of materials.
● Unstable or dangerous fumes. This is extremely unusual; however, it can happen if the mixture ratio is not correct. The foam will usually cure almost immediately once it is sprayed, and certainly within a few hours. If it fails to set, the fumes can be harmful. For this reason, it is essential that you choose a good contractor for your project.

Spray Foam Roof Insulation Problems And Pitfalls

There are so many reasons to choose spray foam insulation including the speed of application, the high thermal values, the ability to get the same thermal value from less depth of material and the fact it lasts many years!

Rotting Of Roof Timbers: When Saturation Sets In

One main concern that is often brought up by home surveyors is the issue of water penetrating the roof and not being able to escape through the spray foam.

This can happen when the roof becomes damaged on the outside, and water gets into the space between the spray foam and the underside of the slates. This can cause condensation due to the temperature difference between in this space compared to the rest of the loft room.

This condensation can saturate the wood trusses and rafters, leading to rotting wood.

The best way to combat this rare issue is to ensure your roof is always in good repair and to choose a spray foam product that is breathable. Ventilation in the roof will also help prevent this issue.

This issue of interstitial condensation has been researched by the Glasgow Caledonian University and it was found that while condensation can be present in an insulated roof, it doesn’t usually lead to wood damage.

This was mostly because the problem only occurs during colder months, as well as when it rains; however, it is not always present.

Unable To Repair The Roof: Why D.I.Y Attempts Are Best Avoided

Another concern is that if spray foam is applied to the underside of the roof slates, it can mean that it is impossible to remove individual slates, and subsequently repair or replace them.

This can be alleviated by spraying onto boards, or another barrier material. Most roofs are constructed with the tiles over a wooden board, so it is rare to apply spray foam to the underside of the tiles directly.

There are so many reasons to choose spray foam insulation including the speed of application, the high thermal values, the ability to get the same thermal value from less depth of material and the fact it lasts many years.

With the right application, and attention to the issues faced by each home, you should have many years of worry free insulation in your roof space. Take the first step today to creating cosier conditions, by calling 0800 1700 636, or by simply clicking the button below!