Loft Insulation

Up to 25% of your home’s heating can be lost through the roof. You may be able to reduce this by up to half if you install loft insulation to the current standard of 270mm (10½”). Loft insulation is a quick, easy and cost-effective way of saving energy, reducing your bills and increasing thermal comfort in the home.

Investment: Up to £170 per year*
Financial Savings: Up to 1,200kg per year
Carbon Dioxide Savings: Up to 1,200kg per year

Could be financed through the Green Deal, paid for at a commercial rate or if you are on benefits funded by ECO or NEST see earlier section on funding schemes  (less if you’re on mains gas or use wood as a fuel) •The Soldiers, Sailors, Air Force Families Association (SSAFA Forces Help), who may be able to provide some assistance, on 01743 344220. •DIY option – there are often good offers on loft insulation packs at B&Q, Wickes and Focus. Look for non-itch versions from recycled plastic. (See below for advice on DIY installation).

Things to consider:-

Cold Water Tanks

A gap in the insulation should be left under any cold water tanks in the loft. The tank should then be insulated on top and round the sides (e.g. with a suitable jacket), continuing down to the level of the joists. Also any pipes in the loft should be fitted with tightly fitting pre-formed lagging or similar to prevent them freezing. Pipe frost protection equipment is now also available if you have pipes which are prone to freezing. See

Loft Hatches

Even if you have a well insulated loft, if your loft hatch is not properly sealed with draught-proofing, heat will be wasted. The hatch lid should also be insulated.

Recessed Ceiling Lights

Should be boxed in with fire-proof materials and insulated over, with a vent on top.


Installers are reluctant to remove too much clutter from your loft and will not lift boarding.

Boarded Lofts

Various insulation products are available to place on top of insulation-filled joists or loft boarding. These are generally available from large DIY retailers and builders merchants. They include supadeck, spacedeck and Kingspan K7. Also try Seconds and Co. of Presteigne, 01544 260501, for useable seconds of Kingspan K7. (


Flat roofs

Flat roofs cannot normally be insulated with the rest of the loft and can be a major source of heat loss. They can be insulated either by attaching insulating plasterboard to the ceiling or taking the ceiling down and insulating between the rafters. Thermilate and Sempatap are also useful because they are cheaper and easier to install although much less effective.

Sempatap is a flexible lining, rather like a 10mm thick insulating wallpaper. Sempatap costs around £18 per square metre.

Thermilate ( make an insulating plaster which has about 90% of the insulating value of Sempatap for the same 10mm thickness.

Sempatap and Thermilate have only limited insulation value compared to rigid phenolic insulation.

Thermilate also make insulating paints which cost around an extra £1 per square metre more than regular paints. Thermilate paint can be added to either Thermilate plaster or Sempatap to increase the insulation value, but is only worth using if you are not able to use an insulated plasterboard.

If you are treating large areas of your roof then the work will come under Building Regulations control (under L1B section 5) and the above options will probably not comply, we suggest you contact your local Council for advice on this.

The use of thin multi-foil insulation is controversial and we do not recommend it.

Tips for DIY Loft Insulation

Please be careful to step only on the ceiling joists when in the loft and wear a mask and gloves. Proper ventilation in the roof space is essential to prevent moisture condensing onto rafters, so ensure adequate ventilation is maintained and do not pack the insulation into the edges of the loft. You also need to make sure that water pipes and cold water tank are lagged and that there is no insulation underneath the tank. Electric cables should if possible be above the insulation. Do not forget to insulate and draught proof the loft hatch. Once insulation has been installed between and level with the top of the joists the second layer should be laid at right-angles, across the joists, to minimise the potential heat loss caused by parallel joints in the insulation and through thermal short-circuits via un-insulated timber joists.

As an alternative to the normal fibre-glass you could use:-

Warmcel recycled newspaper
01938 500643

Isonate – hemp and recycled cotton
01248 388486

Innotherm, recycled cotton
0114 2499 459

Eco-wool (recycled plastic bottles)
Available from B+Q
01743 469100

Precious Earth (Knighton) – various insulation options
01547 528080