Fitting Insulation: A Complete Guide

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Even more wasteful than an uninsulated loft, walls without insulation account for about a third of heat lost. Houses built before the 1990s may not have any wall insulation, so it's worth sorting this out.

How you insulate walls depends on what type they are.

Cavity walls – likely to be found in houses built since the 1920s – have two layers with a gap in between. Insulation can be put into the gap. It needs to be blown in from the outside through small holes.

You will need to have it professionally installed by a member of The National Insulation Association, The Cavity Insulation Guarantee Agency or The British Board of Agrément.

Solid walls lose more heat than cavity walls, and are likely to be found in homes built before 1920. They can be insulated internally or externally.

Inside the home, rigid insulation boards can be fitted to the walls, or stud walls filled with mineral wool fibre built. On the downside, internal insulation will reduce the floor area of rooms a bit, and means skirting boards and door frames will need to be re-fitted.

Alternatively, you can insulate walls externally, using render or cladding. Be aware that you might need planning permission for this. Find more information on the government's planning portal.

Additionally, insulation of solid walls needs to comply with building regulations. A professional installer should deal with this for you. If you remove or replace more than half of the internal plaster or external render, or are dry lining a wall you have to meet the building regulations standards in any case.

The Energy Saving Trust has a list of recommended external wall insulation products. You can find approved installers through the Insulated Render & Cladding Association or the National Insulation Association.

Draught-Proofing Windows

Improve your windows, and lower energy bills. Generally, repairing or replacing windows doesn’t need planning permission, but if you live in a listed building or in a conservation area, you’ll need to check with the planning office at your local authority.

If you have single glazing, replacing it with double or triple glazed versions will reduce heat loss and draughts. Building regulations apply to replacement glazing. If they’re installed by someone registered with a competent person scheme such as BSI, CERTASS, FENSA or Network VEKA, the installer will be able to ensure the work complies.

The Energy Saving Trust has a list of recommended glazing products.

If you live in a conservation area or listed building, talk to your local authority about what you are able to do to improve window insulation. For these homes, or if you cannot afford double glazing, secondary glazing fitted inside your home could be an option.

Heavy lined curtains and shutters are other possible solutions. You can also draught-proof existing windows with foam, metal or plastic strips, available from DIY stores.

Insulating Floors

Don’t neglect floors when you’re improving your home's insulation.

  • You can use sealant – available from DIY stores – to fix gaps around skirting boards and floors.
  • Suspended timber floors, which are found in older homes, can be insulated. The floorboards need to be lifted and mineral wool insulation supported by netting put between the joists. When you’re adding insulation to floors, the work needs to comply with building regulations. An installer should arrange this for you, but if you’re DIYing, you’ll be responsible for this. Contact building control at your local authority to find out more.

How To Get A Grant

Grants for energy-saving measures including loft and cavity wall insulation are available. To find out what’s on offer, visit the grants and discounts database of the Energy Saving Trust.

Certain energy-saving work, such as draught proofing, and wall, floor and loft insulation, qualifies for a lower rate of VAT on materials, equipment and labour. Find out more from the HMRC.

More Information has advice on saving energy and money at home.


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