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Home & garden.

30 June 2021

Installing blanket insulation

Blanket insulation is the most common type of insulation and is sold in rolls, which are laid down between the flooring joists in your loft.
Which?Editorial team
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Everything you need to know about blanket insulation, including whether you can fit it yourself.

Thinking of installing blanket insulation in your home? Then keep reading, as we reveal how to fit it and what you need to do to prepare your loft.

Fitting blanket insulation

Rolls of blanket insulation come in various different widths to match to your loft, so start by measuring the distance between joists and buying the nearest size.

Ideally it should fit neatly between the joists. To calculate the right amount, measure the length of the floor space to be covered. Don't stretch or tear blanket insulation – use scissors if it needs to be cut.

Unroll the insulation blanket and lay it flat between loft joists. If possible, add a further layer of blanket insulation across both the joists and the lower layer of insulation. Be careful not to squash the insulation down. 

If you want to use your loft for storage, you can place boards down backed with further insulation over the top, or you may need to raise the level of the floor to ensure that the 270mm recommended insulation is achieved. If you’re not sure of the best option, contact an installer for a professional opinion.

DIY or get a professional?

Confident DIYers should be able to lay this type of insulation relatively easily themselves – but you should always refer to the manufacturer’s instructions to ensure you’re fitting it correctly and getting the most out of your insulation.

Some insulation grants and offers are still available from some of the energy companies. The discounted materials and installation rates on offer mean that, in some cases, getting a professional to fit your insulation could be cheaper, or even free, versus doing it yourself. 

Before installing insulation

Each type of insulation is fitted differently, but most blanket insulation can be installed as a DIY project. Whatever type of insulation you choose, you’ll need to make a few preparations before you start.

Clearing your loft

Even if you’re getting a professional loft insulation installer to complete the work for you, you’ll usually need to clear your loft before they arrive.


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, local electrician by visiting Which? Trusted Traders and searching in your area. 

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.

If you’re installing insulation to help cut your energy bills, you can also save money by being on the best energy deal. Use our independent switching site, Which? Switch, to make sure you’re on the cheapest energy tariff.