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Home & garden.

30 June 2021

Installing loose-fill insulation

We explain how loose-fill loft insulation works, as well as revealing some top preparations tips to get your home ready for loose-fill insulation.
Which?Editorial team
Loosefillinsulation 450368

Thinking of installing loose-fill loft insulation? Then read on as we reveal all you need to know.

Loose-fill loft insulation is made from light materials, such as cork granules or even recycled newspaper, which is evenly spread in the gaps between the joists.

Loose-fill insulation material comes in bags. Because you simply pour the material from the bag to lay it, it's a fairly easy task to complete yourself. But make sure your loft is properly prepared first.

Fitting loose-fill insulation

Work out the floor space in square metres – you'll need approximately 200 litres of material to cover each square metre to a depth of 200mm.

Before laying your loose-fill loft insulation, ensure the space between the joists is relatively dust-free. You should also check the depth of the joists is sufficient to hold an acceptable level of loose-fill insulation.

The material should be poured between the joists in the roof space, ensuring there are no cracks or holes in the ceiling. Make sure you remember to brush or rake between the joists so the fill is level.

If you’re not fitting boarding over the loose fill, check the level of the material during the winter months. High winds can unsettle loose fill insulation and blow it around your home’s roof space.

To insulate a loft hatch, it’s best to use blanket material held in place by plastic or an old sheet.

When is loose-fill loft insulation suitable?

Loose-fill loft insulation works well in hard-to-reach or awkwardly shaped sections. It’s also a suitable top-up material if your loft has some insulation already.

Loft insulation preparation tips

Even if you’re not fitting loft insulation yourself, you still need to do some preparation before the work takes place.

Clearing your loft

You’ll usually need to clear your loft before the professional loft insulation fitter arrives.


Wiring needs to be dealt with safely. Wires should be kept above the insulation but not stretched if they don’t comfortably reach. An electrician will be able to reroute any problematic wiring. 

You can find a recommended electrician in your area by visiting Which? Trusted Traders. You can also use our Trusted Trader search tool below.

Pipes and tanks

Pipework and tanks in the loft should also be insulated correctly, as less heat will be escaping into the loft and protecting pipes from freezing.

If in doubt

Insulation must be installed following the manufacturer’s instructions to achieve the full benefit. If you’re unsure about any aspect of insulating your loft, you should contact a professional insulation fitter.

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