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15 Jan 2024

What thickness is recommended for loft insulation?

Tansy Dando
Wealth and Business Writer

Home insulation is an important factor in keeping your home comfortable and your energy bills low. When it comes to insulating your loft, however, there are several varieties of material and different thicknesses to choose from — which should you go for? 

Read on for all you need to know about recommended loft insulation thickness and which might be best for your home. 

What is loft insulation?

Before we look at loft insulation thickness options, let’s explore what this form of home insulation does. Ultimately, loft insulation helps keep warmth in when the weather is cold and makes sure your property is cool in the summer. It’s usually made from materials such as fibreglass, wool, or foam, and it’s available in different thicknesses.

Loft insulation works by trapping heat in the loft or attic, making it less likely to escape through the roof. 

Loft insulation is an important part of any energy-saving strategy and can be used in conjunction with other measures such as double-glazing and cavity wall insulation. It’s an excellent way to reduce your energy consumption and keep your bills low.

A note on safety: If you’re considering a loft conversion or want to replace your attic insulation, it’s important to get an asbestos survey carried out. If your attic space contains asbestos, you’ll need to hire a professional to remove it.

How thick is loft insulation meant to be?

When searching for the best loft insulation, you may have noticed a range of thicknesses on offer. The most common loft insulation thickness is around 270mm, but there are also options as thin as 100mm available. In the 1980s, many people would have been asking “is 50mm enough for loft insulation?” But now we know that anything below 100mm is going to offer very poor insulation.

Be aware that, since 2003, building regulations state that insulation in new builds must be a minimum of 270mm thick, regardless of material. 

If you’re adding new insulation to an existing space that’s already insulated, look at the insulation thickness already installed. And if the insulation in your attic or loft is thinner than 270mm, you’d benefit from adding more layers or replacing it completely with something thicker.

In general, the thicker the loft insulation, the more effective it will be at preventing heat loss. However, thicker loft insulation can also be more expensive to install. As a result, it’s important to weigh your options carefully and choose the loft insulation thickness that is right for you.

Can you have too much loft insulation?

Some people suggest that too much loft insulation can cause damp issues however, this is unlikely. Installing insulation that’s thicker than 270mm shouldn’t result in damage. However, it probably won’t offer a huge amount of benefit either. 

Beyond 270mm, you could end up spending excess money with no real return.

What insulation should I use for a loft conversion?

As previously mentioned, 270mm is the legal requirement for a new build. For a loft conversion, current regulations state you must ensure:

  • 270mm thickness for fibre or wood insulation

  • 175mm for board insulation

  • 125mm of high-performance spray foam.

For an attic conversion with a pitched roof, your best bet is to insulate between the roof’s joists. This will ensure the space is warm and comfortable so you can use it as a living space. 

Do you share a roof with a neighbour? If so, it’s best to insulate your roof both between and under the rafters. When doing so, make sure that you leave 50mm of space above the insulation to allow for ventilation.

Find great deals on loft insulation with SpotDif

Whether you’re adding a layer of loft insulation to your attic space, replacing it all, or carrying out a loft conversion, make sure you find a reliable, professional insulation fitter. 

At SpotDif, we compare hundreds of deals from insulation companies in your local area so you can get excellent service at a great price. Start your search and give your property the thermal boost it deserves.

Tansy Dando
Wealth and Business Writer
I aim to bring clarity to the complex sectors of wealth and business with researched content designed to help you make the best financial decisions for your needs.
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