Before you get started

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.

Check that your 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. When laying insulation leave a 25mm gap at the eaves to make sure proper ventilation continues.

If you are considering insulating the loft between the rafters, ie directly under the roof, you must seek professional advice. Insulating between and below the rafters under most circumstances is only carried out if you wish to convert loft space into a living area.

Creating a storage area in your loft is an inexpensive and straightforward project. Use Loft Legs to allow loft panels to be raised above the loft insulation which avoids compressing it and reducing its effectiveness.

Do not insulate directly under a cold water tank (unless the tank is elevated by at least 300mm). Instead insulate 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.

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.


Insulate a loft


Make sure that you have walking boards to work off when working in the loft. You must not step between joists. Chipboard loft panels are ideal.


Unwrap the insulation and break into rolls following the manufacturer's pre-cut guidelines around the roll. This will break up the roll into manageable widths.


Roll out the lengths of insulation between the joists, gently pushing it into position. Do not compress it or its ability to insulate will be lessened.


Alternatively, if you are using encapsulated insulation, there is no need to unwrap it. You simply roll it out, in its packaging, in between the joists.


When a roll finishes and you still have a gap to fill to the end of a row, you can trim insulation to length using scissors or a retractable knife.


If you need to join lengths, simply butt the end of one length up against the next. You do not need to overlap the insulation material.


When you have completed the first layer, to build up to the required level of 270mm, run the next layer at right angles to the first across the joists.


If you have electrical cables in the loft, they should not be left below the insulation, so carefully lift any wires to sit on top of the insulation.


Any pipes in the loft area should be lagged using pipe insulation. This simply splits down one side and is slipped over the pipes.


Corners must be mitred to produce a tight join between lengths of pipe insulation. Cut using an old saw and a mitre box.


Butt join any straight cuts on the pipe insulation and be as accurate as possible when positioning mitred sections at corners.


When you have covered all pipes, tape all joints to ensure that the pipes are tightly sealed in the insulation material.