As much as 20% of your energy bill can be saved by effective loft insulation. Because heat rises, insulating a loft can be especially effective.
When insulating a loft, a depth of at least 150mm (6inches) is recommended. In many older properties, shallow joists in lofts restrict depth for loose-fill insulation.
It is a quick and easy job to lay the insulation material between the joists. The various methods of loft insulation are summarised below.
Whichever method you choose, it is worth remembering that mineral fibre and rock fibre are proofed against rot, vermin and damp. These materials are also non-flammable.
Glass fibre, foil-backed felt, rock fibre or mineral fibre blanket insulation is available by roll. These rolls fit snugly between the joists. This is probably the most common type of insulation.
Rolls are available in 75mm (3inches) and 100mm (4 inches) thickness. The width of rolls range from 300mm (1 foot) to 1200mm (4 feet). The lengths of the rolls range from 5m (16 feet) to 9.4m (30 feet).
Cork granules, exfoliated vermiculite, mineral wool or cellulose fibre are all forms of loose fill insulation. This may not be the best method to use in a very draughty loft space, as the draught can cause the fibre to blow about in high winds.
However it is easy to apply and is especially useful for areas where joists are irregularly spaced and where pipes or other obstructions make it difficult to lay a blanket insulator.
If you intend to use the attic area, insulate the sloping surfaces of the roof instead of the floor. Sheet insulation can be fixed between the rafters. Semi rigid batts of mineral fibre or fibre glass tend to give better results than lightweight rolls and only thin sheets are required, especially if the finish is covered with plasterboard.
Always allow sufficient space between the insulator and the roof slates or tiles to allow for ventilation, and thus avoid condensation.
A professional contractor can be employed to blow fibrous inter joist insulation, via a hose. This may not be the best method to use in a very draughty loft space, as the draught can cause the fibre to blow about in high winds. The contractor should be able to advise you.