Heat rises, and in an uninsulated home a quarter of your heat is lost through the roof.
Insulating your loft, attic or flat roof is a simple and effective way to reduce that waste, thereby lowering your heating bills.
It is currently recommended that loft insulation is installed to a depth of 270mm if using mineral wool. The Energy Saving Trust estimates that you can save up to £180 by insulating your loft, giving a payback time of 2 – 5 years.
What type of loft insulation should I chose?
Easy Access: If access to your loft is easy and your joists are regular, you can use rolls of mineral wool insulation. This is a relatively easy job and can be carried out by a competent householder.
Difficult access: If your loft is hard to access, a professional installer can install ‘blown insulation’ using specialist equipment. The job is quick to complete and fire-retardant material is used.
Irregular Spaces: If your loft space is irregular, the joists are the wrong distance apart for rolls of mineral wool, or there are lots of obstructions that make laying matting tricky, you can use loose-fill insulation. Loose fill insulation is sold in bags as cork granules, vermiculite, mineral wool or cellulose fibre, which can be poured between the joists to the right depth. This can be done by a competent DIY-er or a professional installer.
Which insulation materials should I chose?
As shown above your choice will depend on a number of factors including access, space, price and whether you wish to use the attic for storage. However rolls of mineral wool are often the most cost effective and can easily be installed between ceiling joists.
If space is limited rigid foam insulation could be worth considering. It is about twice as efficient at insulating so takes up half the space, but it is more expensive, and must be cut accurately to size, and any gaps caulked. Other options include sheep’s wool, blown fibre and hemp.
Can I insulate a flat roof?
A flat roof should preferably be insulated from above. This can be carried out by adding a layer of rigid insulation board on top of the roof's weatherproof layer, or directly on top of the timber roof surface with a new weatherproof layer on top of the insulation. It makes sense to do this when the roof covering needs replacing. It is possible to insulate a flat roof from underneath, but it is important to consider potential condensation problems if not done correctly.
Insulating your loft will keep your house warmer but make the roof space above colder. It is possible, therefore, that pipes and water tanks could freeze, so these should be insulated too. The cooler air in your insulated loft could also increase draughts through your loft hatch. To prevent this, you can fit an insulated loft hatch and put strips of draught-excluding material around the edges of the frame.
Insulating your roof could also make existing damp or condensation problems worse on other elements of the house. If you have damp problems, get professional advice before installing insulation to see if you can fix these problems first.