Roof and loft
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In an uninsulated home, around 35 percent of heat loss is through the walls and 25 percent is lost through the roof. The remaining 40 percent is lost through doors, windows and the floor. The better insulated your home is the less heat you will be losing, meaning you do not need to run your heating as much (saving you money!).
Insulating your property will help reduce your energy consumption and lower your fuel bills. Insulation can also help alleviate damp, making it a healthier home to live in.
Heat energy is transferred from homes by conduction through the walls, floor, roof and windows. It is also transferred from homes by convection. For example, cold air can enter the house through gaps in doors and windows, and convection currents can transfer heat energy in the loft to the roof tiles.
Choosing loft insulation
Easy access and regular joists
If your loft is easy to access and has no damp or condensation problems it should be easy
to insulate. It is possible to do it yourself.
If access is easy and your loft joists are regular, you can use rolls of mineral wool insulation.
The first layer is laid between the joists – the horizontal beams that make up the floor of the loft – then another layer is laid at right angles to cover the joists and make the insulation up to the required depth. This can be done by someone competent in DIY or a professional installer.
Storage or living space
If you plan to use the loft or attic for storage, you will want to lay boards over the joists. Unfortunately, if you only insulate between the joists before doing this, the insulation won't be thick enough.
To get enough insulation you can do the following:
Insulate between the joists with mineral wool and then lay rigid insulation boards on top, with wooden boarding on top of that. You can buy
insulation board pre-bonded to floor boarding to make the job easier. Or raise the level of the floor so you can fit enough mineral wool beneath the new floor level.
If you want to use your loft as a living space, you can insulate the roof instead of the floor by fixing rigid insulation boards between the roof rafters. Boards must be cut to the correct width so that they fit snugly between the rafters. They can then be covered by plasterboard. Rafters aren't usually very deep, so to get the best performance you may have to insulate over them as well, using insulated plasterboard. If there isn't room to do this, make sure you use the highest performance insulation board.
Inaccessible loft spaces
If your loft is hard to access, you can have blown insulation installed by a professional, who will use specialist equipment to blow loose, fire-retardant insulation material made of cellulose fibre or mineral wool into the loft. This doesn't usually take more than a few hours.
A flat roof should preferably be insulated from above. A layer of rigid insulation board can be added either 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. This is best done when the roof covering needs replacing anyway. If your flat roof needs to be replaced anyway you must now insulate it to comply with building regulations.
It is possible to insulate a flat roof from underneath, but this can lead to condensation problems if not completed correctly.
Installing flat roof insulation could save you similar amounts on your heating bills to loft insulation. The savings will vary depending on how much of the property has a flat roof.
Insulation stops heat escaping from living spaces, so it will make your loft space cooler, which could make existing damp or condensation problems worse. Get professional advice before installing insulation to see if you can fix the damp problems first.
Pipes, water tank and loft hatch
Insulating between the joists of your loft will keep your house warmer but make the roof space above colder. Pipes and water tanks will be more likely to freeze, so you will need to insulate them. If your water tanks are some distance from the loft hatch, you will also need something to walk on for safe access.
The cooler air in your insulated loft could mean that cold draughts come through the loft hatch. To prevent this fit an insulated loft hatch and put strips of draught-excluding material around the hatch edges.