The Loft

The loft Heat rises, and a lot of it is lost through the roof. Without doubt, the best place to start is with the loft. With a payback period of two years or less, if you are starting from a position of having no insulation at all, you will soon be saving a lot of money.

Insulating a loft, especially in an old house, is a really dusty job so you should equip yourself with safety clothing - overalls, gloves, eye protectors and face mask. Even if your loft is clean, you will still need protection when handling glass-fibre as it can cause skin irritation.

There are two ways to insulate loft floors - using blanket or loose-lay material.

The recommended thickness of insulation is 200mm (8in) but you may have to use 100mm (4in) if that is the height of your joists and you intend to board over the loft. Alternatively, build up the joists with strips of wood.

Blanket insulation is unrolled between the joists. It comes in two widths - 370mm (15in), which matches the joist spacing in older houses, and 600mm (24in) for more modern houses. It is in thicknesses of 100mm, 150mm and 200mm (4in, 6in and 8in).

Start at one side of the loft and unroll the material, working towards the middle (2). Tuck the end of the roll down into the eaves - but don't completely block them as it is important to get some ventilation into the loft to prevent condensation. As the loft will now be colder, warm, moist air from inside the house will condense on the cold roof timbers. If you prefer, fit eaves' ventilators to ensure an air flow.

Make sure you have light up in the loft while you are working - if there isn't a permanent light up there then get an extension cable and a lamp, or a large torch. Stand only on the joists, never between them, or you are likely to put your foot through the ceiling. Provide a series of boards to tread on, each one spanning at least three joists.

When you reach the middle, cut the insulation, go to the other end of the loft and start again, butting up the meeting edges in the middle. Repeat for each joist space. Tuck the blanket under electric wiring to avoid the risk of overheating.

Loose-fill fibre comes in bags which are tipped out between the joists and levelled off with the tops of the joists using a piece of hardboard (3).

It needs no cutting or fitting and is easier to use in lofts where the joist spacing is not of a standard size. It is also ideal for topping-up existing insulation of any kind.

Insulate the loft hatch by fixing a glass-fibre blanket to it. To keep the blanket in place, tap nails into each corner of the hatch and criss-cross string between them. In confined roofs, the spaces in between the rafters can be insulated with expanded-polystyrene boards which are compressed and squeezed into the spaces. They are suitable for spacings of 320mm to 395mm (13in to 16in).