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Roof insulation

Without loft insulation you could be losing as much as 15% of your heating costs through your roof. If you currently have no loft insulation and you install the recommended 270mm (11 inches) depth you could save around £150 per year on your heating bills and around 1 tonne of carbon dioxide per year.

Roof insulationIf 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. Insulating your loft is a simple and effective way to reduce your heating bills and you can even do it yourself. The good news is that insulating your loft with loft insulation blankets, often referred to as 'quilts' can be a pretty straightforward job for either an installer or a competent 'DIY-er'. It needs to be done to a high standard to avoid unnecessary wastage so if you don't feel sufficiently confident that you can do it yourself you should call an installer.

The Peterborough thermal study

To help see which buildings in Peterborough have high heat losses through their roofs an Aerial Thermal Survey was done in early March 2009 by Blue Sky International on behalf of Peterborough City Council.

Heat Loss




Find out how much heat my roof loses

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Frequently Asked Questions

Where do I start trying to install roof insulation?

Firstly its worth finding out how much roof insulation you currently have to see how much insulation you will need, remember you may just need a top up. These days, if you are fitting the most common insulation material, mineral wool, the recommended depth of loft insulation is 270mm. 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.

Next if you wish to find a professional to install your roof insulation - check out recommended accredited suppliers and installers

If installing yourself

Firstly chose the form of insulation you will require of which there are three main types:

  • Quilts - mineral wool and natural wool
  • Blown insulation - mineral wool and Cellulose
  • Boards - expanded/extruded polystyrene

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

Rolls of loft insulation material should be placed between the joints in your roof space, a total of 11 inches is sufficient to prevent excessive heat losses through your roof and save you money. Leave a gap where the rafters and ceiling joists meet, as the timbers at the edge of your roof need ventilation to prevent rotting. Don't forget to insulate your roof access trap door and fit some draught proofing strip to the frame. When working in the roof space be careful to tread only on the timbers, and mind your head. You should wear gloves, when installing as the glass fibre may irritate the skin.

If you'd like to use your loft for living space, then you could look at insulating the roof of the loft instead. This is usually done by insulating between the roof rafters using rigid insulation boards. Alternatively 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 initial cost outlay but you will see greater savings.

Payback periods

  Annual savings Installed costs Pay back CO2 saving
Roof insulation Around £205 Around £250 Around 1 yr 1 tonne
Cavity wall insulation Around £160 Around £250 Around 2 yrs 800 kg
Solid wall insulation - internal  Around £75-100 Around £650 Around 6 yrs 2.3 tonnes
Solid wall insulation - external Around £500 Around £3500-6000 Around 11-15 yrs 2.5 tonnes
Hot water jacket Around £40 Around £20 Around 5 months 200 kg