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How to insulate
your loft

If you want to make your home warmer and save money on your energy bills then insulating your loft is the first place to start.

 
INSULATION PROJECT CHECKLIST
MATERIALS TOOLS SAFETY EQUIPMENT
flooring-heading.jpg Stay Safe

Ensure the loft is well lit and use suitable crawling boards spanning at least three joists to stand on (loft pan els are ideal). Only stand on the joists if you have to, but never in between them. Always wear a mask and gloves when working with loft insulation.

1
Get
Prepared

 

Fig. 1 Get prepared
    2 bed Semi/Terrace 50m2 3 bed Terrace 60m2 3 bed Semi 80m2
  COVERAGE APPROXIMATE NUMBER OF LOFT ROLLS NEEDED
100mm Bottom Layer 11.08m2 5 6 8
170mm Top Layer 6.47m2 8 10 13
200mm Super Top Layer 5.61m2 9 11 15

CALCULATE HOW MUCH LOFT ROLL YOU NEED

We recommend at least 270mm of loft insulation: 100mm loft roll between joists and 170mm roll cross-laid on top. 200mm roll is an option instead of 170mm and gives you even more energy efficiency. If you have insulation between ceiling joists already, make sure it finishes level with the top of the joists. If not you will need to top it up.

Determine the area of your loft by multiplying the length by the width. Deduct 10% from the area for 100mm roll to allow for joists. Divide the area by the loft roll pack coverage to get the number of rolls required.

CLEAR THE LOFT

Remove any objects in the loft and lift any boards (if present).

CHECK THAT THE LOFT IS PROPERLY VENTILATED

There will either be an opening at the eaves where the pitched roof meets the external wall or proprietary ventilators in the pitch of the roof. If neither are present then ventilation must be installed, and specialist advice should be sought.

2
Install
your loft roll

Insulation must not be laid over electrical cables. Lift cables a bove all loft roll and either use cable clips to attach them to roof beams or lay the cable on top of the insulation. To prevent overheating and any fire risk, recessed downlights should be fitted with a downlight cover which allows the insulation to be laid over the top.

ROLL BETWEEN THE JOISTS

Measure the space between the joists, they tend to be either at 400mm or 600mm centres. Before removing packaging, cut the loft roll with a handsaw to the appropriate width using the dotted cutting lines on the packaging. Start laying the roll between the joists from the eaves (Fig. 1), ensuring the wall plate is covered. Leave a 25mm gap at the eaves end to allow for ventilation. Work towards the centre of the loft, pressing the insulation down gently into place. Cut to length with a knife and butt joint where necessary.

INSTALL LOFT LEGS TO CREATE A STORAGE AREA

If you want to create a boarded storage area above your insulation then this is the point to start. See the section on the opposite page for instructions.

OVERLAY WITH A 170MM LOFT ROLL

Cross-lay 170mm loft roll over the 100m roll and ceiling joists (Fig. 2. Ensure the loft area is completely covered except directly under a cold water tank (unless the tank is elevated by at least 300mm). Insulation should be continuous to maximise energy efficiency and energy saving.

INSULATE THE LOFT HATCH

Insulate your loft hatch using appropriate draught seals and fixing polystyrene to the inside of the hatch using PVA Adhesive.

INSULATE PIPES & THE COLD WATER TANK

Insulating your loft increases the likelihood of pipes and tanks freezing. Fit pipe insulation to pipes, cutting it to length with a snap-off knife and taping it to make sure of a snug fit. A cold water tank will need insulating with a tank jacket. These come in various sizes, so you will need to measure the size of your cold water tank. Alternatively, for larger tanks, place a polystyrene sheet on the top of the tank and run the loft insulation up the sides and tie in place using string. Ensure there are no gaps (Fig. 3).