Things to think about when insulating lofts
- Make sure you have a safe working platform when working in the loft, and wear protective gloves, a dust mask and goggles. Overalls will also prevent dust and fibres lodging in your clothes.
- The regulation depth for loft blanket insulation is around 30cm. You will need to lay 15cm of insulation between the joists and a further layer across the top of the joists to achieve this depth.
- To estimate quantity required, divide the loft area in square metres by the area of one roll, which should be marked on the packaging. However, check the depth of roll you are buying as it can be sold in 5cm, 10cm and 15cm depths. Therefore, if you choose 10cm depth rolls, you will need three times the quantity to be up to the regulation level of a 30cm depth.
- Laying loft insulation will save you money by reducing your heating bills. You can also help the environment
- If the loft space is ventilated with eaves ventilators, leave a small gap at the eaves to allow ventilation of the loft area to continue.
- Laying a plastic membrane between joists before laying insulation will prevent moist air entering the insulation and loft space. With no membrane, you could have condensation problems.
- Insulation between joists is shown in this leaflet where the loft space is not being used as a living area. 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 the loft space into a living area. The technique used for insulating between rafters varies considerably according to how the loft space is ventilated, what type of roofing felt you have, what depth of rafters you have, and many other issues that are tightly regulated.
- To build a storage platform you may need to increase joist depth to raise them over the top of the insulation layers. Fix treated timber (10 x 5cm) on top of existing joists; then add chipboard loft panels. Panels must have holes drilled in them to allow the passage of water vapour into the ventilated loft. Drill rows of 10mm holes in the loft boards at a minimum 100mm centres.
- Do not insulate below water tanks in the loft. Instead use purpose-made insulation jackets to protect the tank from the cold.
- Any electrical fittings, such as spotlights in the room below, must be cut around to avoid them overheating. Most manufacturers recommend a minimum 7.5cm gap around the fitting.
Step by step guide to insulating a loft:
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- Step 1
- Make sure that you have walking boards to work off when working in the loft. You must not step between joists. Chipboard storage panels are ideal.
- Step 2
- 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.
- Step 3
- 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.
- Step 4
- 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.
- Step 5
- 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 craft knife.
- Step 6
- 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.
- Step 7
- When you have completed the first layer, to build up to the regulation level of 30cm, run the next layer at right angles to the first across the joists.
- Step 8
- 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.
- Step 9
- Any pipes in the loft area should be lagged using pipe insulation. This simply splits down one side and is slipped over the pipes.
- Step 10
- Corners must be mitred to produce a tight join between lengths of pipe Insulation. Cut using an old saw and a mitre block.
- Step 11
- Butt join any straight cuts on the pipe insulation and be as accurate as possible when positioning mitred sections at corners.
- Step 12
- When you have covered all pipes, tape all joints to ensure that the pipes are tightly sealed in the insulation material.
The expert practical advice contained in the guide assists you in carrying out your home improvement projects both safely and successfully.
If in doubt take professional advice and always follow manufacturers’ instructions
