What thickness is recommended for loft insulation?

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 thickness to choose from – which should you go for? 

Read on for all you need to know about loft insulation thicknesses and which might be best for your home. You can find great local deals on insulation with SpotDif.

What is loft insulation?

Loft insulation helps keep warmth in when the weather is cold and makes sure your home is cool in the summer. Usually, it’s 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. Back 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 just be wasting money.

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, or 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.

Loft conversion

Find great deals on loft insulation with SpotDif

Whether you’re adding a layer of 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. 

Browse our home deals today.


Chelsea Showering is a Specialist in Home Services for Spotdif, a business that deals in the UK. Chelsea is highly professional and creative, and her clients appreciate her dedication to their satisfaction.

After completing her education, Chelsea started working for Spotdif and has excelled in her role. She is an expert in home services and is regularly called upon to provide advice to clients. Chelsea is a creative thinker and approaches each task with enthusiasm. She loves her job and takes great pride in providing excellent service to clients.


Chelsea Showering

Specialist in Home Services

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