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Where to insulate

• Ceilings: save 20-40% on heating and cooling costs
• External walls: save an additional 10-60% on energy costs
• Floor: save another 5-10% on energy costs.

Existing homes can easily have insulation installed in the ceiling and under timber floors if crawl space is available. Walls can be insulated during re-cladding or replastering. Specialised products are also available to insulate existing walls.

Insulating both the roof and ceiling will ensure a home is adequately insulated from the outside elements. Roof insulation, such as reflective foil (sarking) or foil backed building blankets, will help to reduce radiant heat from entering the home in summer and will also provide some winter thermal protection.

Ceiling insulation will help to slow the transfer of heat into or out of the home. If the ceiling was not insulated, warm air generated by heating systems in winter would end up in the roof space (remember that hot air rises), while in summer, heat building up in the roof space may move into the home.

These products may also have other benefits. For example, sarking under tiles can help to waterproof a roof. A building blanket under a metal roof will provide some sound insulation (deadening the sound of rain) and protect the metal from corrosion by reducing condensation on the underside of the roof.

What else should I consider?

• Face masks, gloves and protective clothing should be worn when in contact with mineral wool (fibreglass and rockwool) and cellulose fibre insulation.
• Cellulose fibre insulation must be treated with a fire retardant during manufacture.
• Expanded and extruded polystyrene is combustible, and should only be installed between fire-resistant surfaces.
• Natural wool is flame resistant, but the quality and fire resistance of individual products may vary. Check that the manufacturer can supply 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 type of installation is worth considering in structures such as cathedral ceilings and flat roofs where air flow may be insufficient to remove water vapour that builds up in the roof space, or where daytime temperatures do not regularly exceed 5ºC.
• Good insulation should be coupled with effective shading of windows and good ventilation in summer to avoid collecting and trapping heat inside the home.
• Reflective foil installed under the roof (sarking) will also reflect large amounts of direct radiation away from the home in summer.
• Bulk insulation materials have good soundproofing qualities. In particular, a building blanket installed directly under metal roofing helps to reduce external noise resulting from wind, rain and hail. If soundproofing is desired between rooms, high density insulation can be installed in internal walls.