Types of blanket loft insulation
This may be glass, mineral or rock fibre and comes in rolls for easy handling.
You will need to look at the information on the packs to decide how many rolls you need. The details will tell you how many square metres can be covered for a given thickness. If your loft is uninsulated, choose 250mm thickness. If you are topping up the thickness of existing insulation, choose one which provides the additional thickness required. Check carefully, as some rolls come pre-split offering two possible thicknesses.
Also check the width between your joists. The standard rolls are about 400mm wide to suit most joists, but wider gaps can be accommodated by trimming.
Laying the blanket insulation
Take the rolls up to the loft while still wrapped. They are very compressed and expand when unwrapped.
When laying the material, lift any electrical cables and clip to the joists. Insulation laid over cables may cause them to overheat.
Do not lay insulation over light fittings from the ceiling below.
Also, do not lay insulation beneath the water tank as the heat rising from below will help to avoid freezing.
Start at one end of the loft. Unwrap the first roll. Trim the end to an angle and place it towards the eaves. But, be careful not to block the air flow at the eaves as this is designed to provide necessary ventilation to the loft space. Unroll and position the blanket between the joists. If the roll is a little wider than the gap between joists, allow it to fold up at the edges. Take care not to compress the material, as its insulation qualities depend in part on the air trapped within it.
Continue unrolling the blanket. Butt join new rolls and continue working your way across the loft trimming at the eaves as before.
Trim the material to fit any odd areas as you go.
At the loft access, cut the blanket to fit the back of the hatch. Cover this with an old piece of sheet and fasten with drawing pins or staples. You may also fit draught excluder, like that used for doors, to prevent unecessary heat loss around the opening .