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Insulating a Loft

Skill Level: Beginner



Loft insulation together with relatively simple draught proofing around the home can save up to 25% on your fuel bill. 25% to 30% of heat generated in the home is lost through the roof – heat rises up and through the house, taking your money with it.
The two most common types of roof insulation are either the roll blanket type, or loose fill materials; with the former being the easiest and most popular.



When insulating your loft you will be working in a somewhat confined space. Unless it has been boarded out you’ll need to tread very carefully as you move about, if you don’t want to go crashing through the bedroom ceiling. One of the first things you must get hold of is a couple of scaffold boards, or some other form of strong timber battens, from which you can work. The second thing you’ll need is adequate light!
You will not need too much in the way of tools to insulate the loft; a craft knife, scissors and perhaps a measuring tape. Wear some form of protective clothing, eye protection, gloves, and a dust mask. These are all important and help prevent skin irritations, dust and fibres in the eyes, and breathing problems. Before you actually start laying the insulation, get it up in the roof space.

Joist Spacing

The spacing between loft joists is usually about 350mm, give or take. Loft insulation blanket generally comes in rolls, and is 400mm wide. This is very handy and means we won’t need to cut it widthways. Just tuck it in to form a nice snug fit.

Electrical Cables and Light Casings

It’s not a good idea to cover electrical wiring and light casings with insulating materials as this can lead to overheating. Lift cables up and lay the insulating blanket underneath them to avoid this, and for easy location in future. Cut around light casings carefully using a utility craft knife.

Roll out the insulating blanket.

Unroll the blanket between two joists, starting at the eave of one end of your loft, but do not take it right into the eave! Make sure you leave it about 50mm short, so air can still enter the loft space through the soffit and freely circulate; this helps prevent condensation. Press the insulating blanket down fairly lightly as you unroll it.

Cut the Blanket.


When you reach the other side of the loft, when the blanket is snugly fitted between the joists, simply cut with a pair of large decorator’s scissors. Remember to leave that short gap at the eave. Where you need to join two lengths of blanket simply butt the two ends together, squashing and pressing the two edges together.


Cold Water Cisterns.

Do not insulate underneath the cold water cistern. This must be kept free to allow the free flow of warm air from the rooms below, which will in turn reduce the risk of the tank freezing up in extremely cold conditions.

Tools you will need:
Indirect Vent Safety Goggles
Indirect Vent Safety Goggles
- Scan Rigger Gloves
Scan Rigger Gloves

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