A well-insulated house keeps warmth exactly where you need it – indoors. Loft insulation is a simple and effective way to reduce your heating bills, improve energy efficiency and is a home improvement you can do yourself.

Before you embark on insulating your loft, you’ll need to make sure it’s in good condition and dry, otherwise the insulation won’t work properly and you could be trapping in dampness and mould. If you’re planning a home retrofit – where improvement works are made to improve the energy efficiency of your home – insulation is the recommended first step, to ensure any other improvements have the maximum results.

Here’s how much a typical installation could cost you, how much you could save on your energy bill by topping up your loft insulation from 120mm to 270mm.

	Typical installation cost	Annual saving
Detached house	£1,100	£35 per year
Semi-detached house	£900	£20 per year
Mid-terrace house	£850	£20 per year
Detached bungalow	£1,2000	£35 per year

(NB These estimates are from the Energy Saving Trust and based on gas-heated homes and on fuel prices as of July 2025, and assuming an unsubsidised insulation cost. The recommended depth of mineral wool insulation is 270mm, but other materials need different depths. Prices will vary.)

Which loft insulation is suitable for your home?

Loft insulation is effective for at least 40 years, and it will pay for itself over and over in that time. Depending on your home type and size, you can save between £210 and £390 on your energy bill each year if your loft is completely uninsulated before you insulate it.

Standard loft insulation

Standard loft insulation is appropriate for most homes. This is where rolls of insulation are laid in between and over the floor joists.

Generally speaking, if your home has an accessible loft with no damp or condensation problems, it will be a good candidate for loft insulation.

Even if you already have some insulation, your loft may need a top-up. The recommended depth for mineral wool insulation – the most common material – is 270mm (about 1ft), but there are other materials (usually more expensive) which require different depths.

You might even be eligible for an insulation grant towards the cost of professional insulation, depending on your circumstances and how much insulation you currently have.

If you have loft insulation at joist level – on the ‘floor’ of the loft – then you do not also need insulation under the sloping part of the roof, unless you intend to use the loft as a living space.

Do-it-yourself

Laying standard loft insulation is usually a straightforward job for a competent DIY-er. Mineral wool insulation can be bought in big rolls from builders’ merchants or DIY stores. See our separate DIY DIY loft insulation page for more information including important factors such as ventilation and safety.

If you need to use your loft for storage, you can use joist extenders to lift boards above the insulation. This will maintain a constant level of insulation throughout your loft space. But make sure the boards aren’t touching the insulation. You’ll need to leave a gap for ventilation to reduce risks of condensation, which can make your loft mouldy.

Blown-in loft insulation

For lofts with difficult access – those with small hatches and very little space – standard loft insulation rolls may not suitable. Instead, you can opt for blown-in insulation. This is where small pieces of insulating material are blown into your loft using specialist equipment. The pieces offer good coverage of your loft as they reach all the nooks and crannies. This is a job for a professional installer and can take a few hours depending on the size of the loft.

But this may not be the right option if you use your loft for storage. Because the coverage is so good, it can be hard to see the joists to place boards over them. And any pressure from the boards can reduce the effectiveness of the insulation.

For more on loft insulation, see our pages on Loft conversions insulation and ventilation and DIY loft insulation.