A-Z of DIY & Building Guides Fitting Insulation

Date Published:

27/05/2008

Fitting Insulation

It makes sense to insulate your home - it's eco-friendly, keeps bills down and the heat in. Here's our guide to what's what.

By Mark Ramuz

Insulating The Loft

No less (and probably more) than a staggering 25 per cent of the heat from a home can be lost through the roof. Start saving money and keeping warm by making sure you have a properly insulated loft. This is an ideal DIY job that doesn't need any special skills. DIY stores sell insulation in various thicknesses so you can top up your old insulation. The total insulation thickness should be at least 270mm.

These materials are itchy but you can now buy encapsulated glass fibre insulation - in other words, the fibres come in a silver wrapping, making it much more user friendly. A 4m roll costs around £10.

Before you start work, use a torch to check that all the exposed wood looks in good condition. Check especially for any dampness or small holes that indicate woodworm. Carry out any repairs or call in a professional.

Measure the distance between your ceiling joists. Insulating mineral fibre is usually sold in 5 to 8m lengths, 370mm wide to fit the standard spacing. If your loft has very uneven spacing or lots of cross rails, use insulation granules which can be poured into any shaped space.

Lofts are dirty places and insulation fibres can irritate the skin so take off your watch and wear a mask, overalls and gloves. For safety, it's also worth putting down some chipboard loft panels to stop you putting your foot though the ceiling below.

Lift all the insulation materials into the loft and unroll the first length so that it fits between the ceiling joists. Start at one end and work your way across the loft. Leave a small 25mm gap between the end of the rolls and the eaves to allow air to circulate. Butt the ends of rolls together. If you have recessed ceiling lights or other wiring laying around, carefully lay the wire on top of the insulation and leave space around each light fitting to prevent overheating.

The loft hatch is often a very cold spot as warm air is drawn up into the loft space. Cut some insulation and fit this over the back of the loft door. Keep it tidy by putting the roll in a bin liner and then attach it with string or tape.

DIY Payback

If you're prepared to get a bit dirty and insulate the loft yourself, material costs will be around £250 for an average house. This could save a hefty £110 per year, meaning a two-year payback time.

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