Which? logo

How to choose the right insulationInsulation benefits

£100 - The amount you can save annually by insulating your loft

Heat lost from your walls, loft and floor can account for up to 35, 25 and 15% of your heating bill respectively. Lofts are the easiest to insulate and by adding insulation you could save up to £100 a year on heating costs.

What you could save with insulation

These figures from the Energy Savings Trust show you can reduce your heating bills by insulating your home and recoup the cost of the insulation before long, especially if you have little or no insulation at present.

Reducing energy bills with loft insulation
Costs/Savings Adding 200mm to existing 50mm of loft insulation 250mm loft insulation where none at present
Cost of fitting
Installer £200 to £230 £220 to £250
DIY from £140 from £170
Annual savings
On fuel bills £20 to £30 £80 to £100
Costs recovered
Installer 7 to 11 years 2 to 3 years
DIY 5 to 7 years around 2 years

Financial help with insulation

Government grants are available to help with the cost of insulation through the Warm Front programme in England.

Grants of up to £2,700 can provide a package of insulation and heating measures tailored to your home - find out more on the DirectGov website or ask your gas or electricity supplier for help. Insulation suppliers are obliged to provide customers with advice on improving the energy efficiency of their homes.

Residents of Northern Ireland may be eligible to receive a Warm Homes grant while those in Wales can apply for the Home Energy Efficiency Scheme.

Home energy-efficiency ratings

Home information packs (Hips) include an Energy Performance Certificate (EPC) showing an overall energy-efficiency rating for you home from A-G.

The energy rating is a key part of a Hip, and ‘A’ represents the most energy-efficient properties and ‘G’ the worst. The EPC also contains advice on how to cut carbon emissions and fuel bills by making home improvements.

Fitting insulation is an effective way of raising your home’s energy efficiency rating. If you don't have insulation installed the EPC will recommend the type and level of insulation required for maximum efficiency.

If you do have loft insulation but it’s deemed to be old or inefficient, the EPC may also recommend necessary improvements.

Other ways to save energy

Draughts can occur around window and door frames, down chimneys, through letterboxes and between skirting boards and floorboards. You could be losing 15% of your heat through draughts and 10% through windows.

Draught proofing, costing from £40, will save you £10 to £15 per year on your heating bills, paying for itself in just three to four years.

See our guide to using less electricity for more tips.

Types of insulation

Insulation acts as a blanket, trapping heat rising from the house below. Even if you already have some insulation, adding more to create the recommended 270mm depth can mean further savings.

Insulation is sold in different forms and materials, and each has pros and cons when it comes to fitting.

Materials range from traditional fibre glass and mineral wool to environmentally friendly insulation such as recycled paper, sheep's wool and hemp. Environmental insulation materials can be more expensive but are from renewable sources and take less energy to produce.

Batt or blanket insulation

This insulation is available in rolls of foil backed felt, rock, glass or mineral fibre and is probably the most common form of insulation.

Pros

  • Straightforward to self-install
  • Some brands use recycled glass or sheep’s wool (which is non-irritant and non toxic)
  • Good for insulating accessible spaces such as exposed wall cavities and some attics

Cons

  • Some materials can irritate the skin so make sure you wear proper protection from the fibres
  • Sheep’s wool is a more expensive insulation option

Loose-fill insulation

Loose-fill insulation is made from a variety of granular or lightweight materials such as cork granules, exfoliated vermiculite, mineral wool or cellulose fibre. Greener types of loose fill insulation include recycled newspaper.

Pros

  • Fits easily between irregularly spaced rafters or around obstructions
  • Useful for topping up existing insulation in attics

Cons

  • Can come loose in draughty lofts
  • Safety equipment and protective clothing needed during installation

Sheet insulation

Sheet insulation is designed for insulating the sloping sides of the roof and is often made from polystyrene, polyurethane or polyisocyanurate boards.

Some sheet insulation boards are available with a fire-resistant, moisture-resistant or decorative covering. Sheet insulation can also be ordered pre-cut to specific sizes for an additional cost.

Pros

  • Greener insulation options include cork, straw and wood board
  • Excellent for insulating loft conversions
  • Can be covered with plasterboard for an attractive finish.
  • High insulating value per unit thickness.
  • Some boards come with their own system of attachment

Cons

  • Synthetic sheet insulation materials use large amounts of energy during production
  • Can be more expensive per level of insulation than other types

Blown fibre insulation

You'll need a professional contractor to install blown fibre insulation - the insulation is blown into the gaps between joists.

Pros

  • Quick and easy insulation to install when done by a professional
  • Greener insulation options include recycled paper or wool
  • Ideal for insulating areas where access is difficult or the use of blanket insulation is impractical
  • Lightweight and convenient to handle and cut

Cons

  • Can be expensive due to the need employ professional help
  • Not recommended for insulating draughty lofts

How to fit insulation

Each type of insulation is fitted differently but most 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.

Before installing insulation

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 re-route any problematic wiring – see our guide to hiring an electrician.

All pipe work and tanks in the loft space should also be insulated correctly since there will no longer be the same amount of heat escaping into the loft space to protect pipes from freezing.

Insulation must be installed following the manufacturer's instructions to achieve the full benefit.

Fitting blanket insulation

Blanket insulation is sold in rolls of different widths 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. Boards can then be placed over the insulated space for easy access in the roof space.

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 the material, ensure the space between the joists is relatively dust-free and that 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. Brush or rake between the joists to ensure the fill is consistently level.

If you're not fitting boarding over the loose fill, check the level of the material during winter months as high winds can unsettle loose fill insulation and blow it around the roof space.

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

Fitting sheet insulation

This type of insulation is fixed between the rafters rather than between joists, and like blanket insulation it can be cut to fit or bought in pre-cut packs.

To avoid condensation build up, always allow sufficient space between the insulation and roof slates or tiles to allow for ventilation.

Fitting blown fibre insulation

In most cases you’ll need to hire a professional to install this type of insulation as it needs to be blown into place with specialist equipment.