All about installation

Whether you're installing loft insulation yourself or calling in a professional, here's an introductory look at what installation involves.

Please don't use this as an installation guide; contact an installer or consult a proper DIY manual when it comes to doing the job.

What insulation materials do you need?

There are three main types of loft insulation:

Quilts - mineral wool and natural wool
Blown insulation - mineral wool and cellulose
Boards - expanded/extruded polystyrene.

Typically, quilts are laid down between the joists - the, horizontal beams that make up the `floor' of the loft - then another layer of insulation is `cross-laid' to cover the joists but there are other solutions if you wish to use the loft for storage or convert the space into a living area.

If the loft is going to be used for storage then you can insulate between the joists and then either use flooring boards backed with further insulation over the top (making sure that the lower insulation isn't squashed down) or you can raise the level of the floor and insulate to the recommended depth. If you are in doubt about the best method, contact an installer.

If you wish to convert the space into a living area, you will need to insulate to keep it warm. Instead of laying insulation between the joists, it is possible to fit rigid insulation boards between the rafters: the sloping timbers that support a pitched roof.

Please remember that while quilts and boards are suitable for DIY-ers to work with, blown insulation should only be installed by professionals with specialist equipment.

Quilts:

Sold in flexible blankets of different thicknesses.
Man made from glass or rock fibre, some of which will have been recycled.
Mineral wool is the most common form of loft insulation quilt in the UK.
You should always wear a protective mask and gloves when insulating your loft with mineral wool.
Natural wool insulation is another form of quilt that's very environmentally friendly.

Blown insulation:

Blown loose into the specific, sectioned-off area to the required depth.
Blown cellulose fibre or mineral wool should only be installed by installers
Cellulose is man-made from newspapers.
Fire resistant

Boards:

Boards are made from expanded / extruded polystyrene - for roof insulation only

Expanded polystyrene (EPS) is polystyrene that's been expanded into foam.
Extruded polystyrene (XPS) is similar but an even better insulator.

What are the best brands of loft insulation?

There's a wide variety of brands and products on the market. To find the best loft insulation for you, look for the Energy Saving Recommended logo. Loft insulation products which carry the logo have met strict criteria, which are set by an independent panel and reviewed each year. This criteria ensures they adhere to applicable British standards and appropriate quality control processes. These products are also designed to make it easy to comply with Building Regulations.

Find out more about Energy Saving Recommended

Here's a full list of Energy Saving Recommended loft insulation products.

How much insulation should you need?

These days, if you are fitting the most common insulation material, mineral wool, the recommended depth of loft insulation is 270mm.

If your loft was insulated a while ago, your insulation may not be deep enough by today's standards - and will be well worth topping up.

However there are other materials out there which have different insulating properties and therefore require different depths.

Basically, the deeper the insulation is in your loft, the less heat you will lose through your roof and the bigger CO₂ and financial savings you will make.

Installing 270mm of insulation in a loft with no insulation will save around a tonne of CO₂ per year. If there was already 50mm of insulation and you topped this up to 270mm, the extra saving would be around 230kg of CO₂ per year.

In the case of `blown' loft insulation, your installer will make sure it's added to the right depth.

How should insulation quilts be laid?

Loft insulation quilts should be laid horizontally between the joists and reach the top of the joist. Typically, this will make the insulation around 100mm to 150mm deep.

More layers should then be added at right angles, to close up any gaps between the joist and the quilt, and to bring the depth to the recommended 270mm.

Important things to remember

Try not to squash down the insulation material. This makes insulation less effective.
Make sure you don't block any air vents, which are there to help prevent condensation. You may need more of them if condensation is a possible problem; a professional can tell you about different ventilation methods like soffit, tile or ridge vents.
All electric wires, cables and light fittings must be kept visible to avoid overheating. If you are in doubt, it may be best to contact an installer.
Always wear a protective mask and gloves when working with mineral wool insulation.

What if you use the loft for storage?

In other words, what if you need a solid `floor' on top of your insulation?

You have four main options:

Insulate horizontally up to the top of the joists, as normal, and then fit boards across them. This will make the insulation a lot shallower than 270mm, so won't save as much energy.
Before you fit any boards, install a second set of joists across your insulated horizontal joists. Then insulate between these too, to bring the total depth of insulation to around 270mm. This will mean more outlay - but greater savings.
Do as in option 1 in just a part of the loft, then insulate the rest of the loft as normal - i.e. at right angles to the joists and up to a depth of 270mm.
Do as in option 1, but instead of using traditional boards, use hard insulation boards. These could be made of the expanded or extruded polystyrene (EPS or XPS) material we mentioned before. This will give you a solid surface and the right level of insulation. Please note: the depth of insulation board required varies depending on the material used.

Remember to insulate your 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. So, without their own insulation, pipes are more likely to freeze.

If there are any water tanks in the loft, they, should be insulated with insulation jackets.

Also, if your water tanks are some distance from the loft hatch, you will need to lay a suitable walk board or similar to provide safe access.

Finally, the cooler air of your insulated loft could mean cold draughts through the hatch. To prevent this, buy an insulated loft hatch from a DIY store and put strips of draught-excluding material around the edges of the frame.

A registered installer will, of course, be able to help with all of these details.

How do you insulate the roof of a loft?

This is usually done by insulating between the roof rafters, using rigid insulation boards made of expanded or extruded polystyrene. Boards must be carefully cut to the right width so that they fit snugly between the rafters.

Rafters aren't usually very deep, but luckily boards insulate more efficiently than quilts. If you really need deeper insulation, insulated plasterboards can also be fitted onto the rafters - although this will make the loft space a little smaller.

How do you find an installer?

Call your local Energy Saving Trust advice centre for free on 0800 512 012. Our advisors there will be happy to put you in touch with a loft insulation installer.

The National Insulation Association website can also provide you with a list of installers.

Installers should take no more than a few hours to insulate your loft. You must clear the loft before they arrive unless you have specifically arranged with the installer to carry this out for you.

Grants and offers

To help with the cost of insulation, there are a range of grants and offers available from the government, local authorities and energy suppliers.

You can also take up grants and offers from any of the energy suppliers, regardless of who supplies your gas and electricity. All energy suppliers provide grants to install loft insulation for free to those aged over 70 or those in receipt of certain benefits.

To find out what's available, call your local Energy Saving Trust advice centre on 0800 512 012 for free, impartial advice. Our advisors will tell you about any special grants or offers available in your area - and whether you can apply for them.

Details of grants and offers can also be found on our grants and offersdatabase.

Tax allowances of up to £1,500 are available until 2015 for Landlords through the Landlords Energy Saving Allowance. This allowance can be used on each of the properties a landlord owns, enabling landlords to claim the costs for cavity wall insulation, loft insulation, solid wall insulation, draught proofing, hot water tank insulation and floor insulation. Visit the HM Revenue & Customs website for more information