How to insulate your loft conversion?

There are several ways to insulate a loft conversion, each with their own advantages and disadvantages.

The two parts of a loft which can be insulated are the floor and the roof. Depending on your budget and plans for the new loft conversion, you may want to do only one of these or both.

There are also two things to insulate for: heat and sound.

Insulating the Roof

Insulating the sloping part of the underside of your roof is done with rigid foam insulation, such as Kingspan. Sheets are cut to size and fixed in place between the rafters.

Virtually all loft conversions should have this. The only types of conversion which would not incorporate this kind of insulation is one which is purely for storage. Even in this case, insulating the underside of the roof is always recommended.

If your property is an older house with a loft which has already been boarded out, you may find that the roof has been insulated already. Good quality, modern insulation is superior to many of the older generations of insulation, so even if you already have some insulation it may still be worth replacing it.

For loft conversions where sound is a factor, you may want to insulate the roof with a product which has sound deadening properties too. Sound insulation will prevent sound coming in or out, which can be useful for:

• Playing loud music
• Recording music
• Making videos
• Having meetings

The structure of a roof is relatively thin compared with most house walls, so there is a good change you will hear loud traffic and other noises unless you insulate against it.

If you plan on playing loud music, DJing or practicing the drums late at night, insulting the underside of the roof could help maintain good relations with your neighbours.

Insulating the Floor

If you have a virgin loft which has never been boarded there is a good chance that you will already have insulation above the ceiling of the top floor of your property.

In many cases, this insulation comes in soft thick rolls which are laid out between the ceiling joists, directly on to the plasterboard or lathe and plaster. These rolls are often deeper than the joists which they sit beside because they are more effective the thicker they are.

If your property already has this type of insulation, it is not recommended that you remove it or squash it down so that you can fix boards directly to the joists. Squashing this insulation reduces its effectiveness and removing it entirely will make the existing top floor of your house feel much colder.

Best practice is to use ‘stools’ which can be fixed directly to the top of the joists and will sit proud of the insulation, allowing the loft to be boarded out without compromising the warmth of the floor below.

You may also wish to explore sound insulation between your loft conversion and the rest of your house if you need peace and quiet in your new space or are planning to make a lot of noise in it.