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You wouldn't throw money out the window, so why let heat escape the same way?

You could cut your heating and cooling costs by up to 40 per cent by insulating the ceiling in your home – even more if you include the walls and flooring.

Insulation in roofs, walls and floors reduces heat-flow into and out of your home. When choosing insulation, the most important factor to consider is the R-value, which measures a material’s capability to resist heat-flow. The greater the value, the better the insulation and the lower your power bill.

diagram of a ceiling diagram of floorboards diagram of a roof


Insulate ceilings to stop losing between 20 and 40 per cent of your heating and cooling. Top up existing ceiling insulation to gain additional performance.


Reduce radiant heat in the summer and gain some winter thermal protection with reflective foil or foil backed building blankets.


Use reflective foil or batts under suspended floors to cut energy costs by a further five to 10 per cent.


Reduce power bills by another five to 10 per cent by insulating walls during recladding or replastering. Specialised products are available to insulate existing walls.

diagram of a downlight

To avoid the risk of fire, don't install bulk insulation within 50mm of chimneys, flues, downlights or exhaust fans. For more information on fire safety, see the Living Greener website.

Wear a face mask and protective clothing when in contact with mineral wool (fibreglass and rockwool) and cellulose fibre insulation, which must be treated with a fire retardant during manufacture.

Care should also be taken when using other materials, including expanded and extruded polystyrene, which is combustible and should only be installed between fire resistant surfaces.

Natural wool is flame resistant, but the quality of individual products varies, so check with the manufacturer for details of independent fire resistance tests.

A layer of non-permeable material (e.g. aluminium foil or polythene sheeting) installed on the inside of bulk insulation provides a barrier to the movement of water vapour to cold surfaces. This is worth considering in structures such as cathedral style ceilings and flat roofs, where airflow may be insufficient to remove any vapour in the roof space, or where daytime temperatures do not regularly exceed 5°C.

Insulation also has great sound-proofing potential. A building blanket under a metal roof will deaden the sound of rain and protect the metal from corrosion, by reducing condensation on the underside of the roof.

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Page last updated: 10 December 2015