Insulating sloping ceilings or dormer windows
Even if you have insulated your loft if you have un-insulated sloping ceilings and /or dormer windows you will still be losing a lot of heat through your roof.
This could be funded through the Green Deal or through ECO or NEST for those on benefits.
The best option for insulation is rigid phenolic foam insulation. This can be placed under the existing sloping ceiling and plasterboarded, or if the ceiling is removed used in combination with insulation between the rafters (it’s important to keep a ventilated gap between any insulation and the roofing felt to avoid condensation problems). Phenolic foam is about 50% more effective per inch as polystyrene equivalents so is very useful where space is tight.
If this is not possible you could use a combination of Sempatap and /or Thermilate.
Sempatap is a flexible lining, rather like a 10mm thick insulating wallpaper. Sempatap costs around £18 per square metre.
Thermilate (www.thermilate.co.uk) 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.