Insulating Your Loft at Focus

Insulating your loft

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A house loses about a quarter of its heat through the roof so it pays to make loft insulation a priority.

It's not a difficult job. Simply aim for at least 150mm (6") of insulation between joists to improve its lagging efficiency. If your existing insulation is less than 150mm thick, top it up now.

Bear in mind, too, that insulation will make the loft space considerably colder than it was, so the cold water tank and any exposed pipes will need lagging.

This small leaflet is intended as a basic guide only. Many of the products for this project will include manufacturers instructions. These instructions should be followed to ensure best results.

Always consider 'safety' before you start any DIY project. Look for the 'Be Safe' sign and read the safety advice.

Essentials:
All available at your local FOCUS store

Insulation rolls or loose lay insulation
Pipe insulation - either lagging or split foam plastic sleeving
Face mask *
Protective gloves *
Loft insulation *
Safety light *
Scissors or sharp knife
Ball of string
Waterproof adhesive tape
Expanding aerosol filler foam

* Warning, care must be taken with these items

Preparing the loft

Begin by checking that access to your loft is secure and that there's an adequate light source. A torch isn't good enough. Inspect the loft for any signs of rot, woodworm or faulty wiring. Check on ventilation too. Condensation can be a real threat unless air can flow freely through gaps in the eaves.

You're going to need a clear floor space, so remove as many stored items as you can, then if possible, vacuum up the dust. Tread carefully, though. If the floor isn't boarded, you must keep your weight on the joists or you'll go right through the ceiling! To be safe, use a board which is thick enough to take your weight and long enough to span at least three joists.

Wear a pair of gloves, a face mask and a pair of overalls. Insulating can be a messy job - and the insulation might irritate your skin and throat.

How much insulation?

The length of a roll of insulation varies according to the thickness, but the 100mm (4") thickness is usually sold in rolls 6.5m long, the 150mm (6") in rolls 5.17m long. Measure the length and width of your house and multiply the two figures to find the size of your loft.

Work sequence

Laying insulation blanket

Starting at the eaves, unroll the blanket between two joists, pressing it down lightly as you go. Leave a gap of about 50mm (2") at the eaves for ventilation. The insulation should completely fill this space between the joists, without any gap

Wear protective gloves, face mask and clothing when handling loft insulation *.

Work from both sides of the loft and cut and butt-fit where the two lengths of insulation join at the centre. Insulate the remainder of the loft in the same way, forming simple butt joints.

If the cold water tank is at ceiling level do not lay insulation beneath it, as warmth from below will help keep the water from freezing.

Lift electrical cables above the insulation so that they do not overheat, if possible, fix them to the sides of the joists with cable clips.

Cut a piece of insulation to fit the loft hatch cover, cover with plastic and then hold in position on the top of the cover using staples or tape. Fit foam draught excluder around the edge of the hatch.

Remember to wear gloves and take care when opening and closing the hatch *.

Laying loose-lay insulation

Loose-lay material is best suited to topping-up existing insulation or for lofts where the joist spacing is irregular. In a draughty loft, it tends to blow about.

To prevent the insulation disappearing down a cavity wall, block the eaves with lengths of timber, wedged between the joists. Seal any holes in the ceiling through which pipes pass with expanding aerosol filler foam.

Empty out the contents of each sack into the space between the joists. With a notched spreader made from hardboard, level the insulation to the required depth.

If the joists are less than 125mm (5") deep, lay the insulation flush with the top of the joists and level with a timber straight-edge. If the cold water tank is at ceiling level do not lay insulation beneath it, as warmth from below will help keep the water from freezing.

Plug any large gaps in a draughty timber floor with slithers of wood planed flush. Smaller gaps can be filled with caulk or decorators fillers. Never seal exterior ventilating bricks. Then cover the whole floor with hardboard, thick underlay and carpet.

Insulating cold storage tanks

Use ordinary blanket insulation, wrapped around the tank and secured with wire, tape or string. Cover the lid too - taking care the fibres do not fall into the tank. If the tank is round, a flexible plastic jacket is quick and easy to fit.

If tank is at ceiling level do not insulate beneath it.

Insulating hot and cold water pipes

All pipes in the loft must be insulated - except those already under loft insulation or within the tank casing.

The easiest method is to use pre-formed, moulded insulation which is split along its length so that you can slip it onto the pipe.

More tedious to fit, but more economical on complicated pipe runs, is pipe lagging. This wraps around the pipe in a spiral and secures with wire, tape or string. Don't leave any gaps. Wrap up the bodies of taps and joints as well.