Around 25% of heat lost from an uninsulated home escapes through the roof. Loft insulation addresses this directly - it's cheap, effective, and pays back in under two years for most households.
It's also the starting point for any heat pump installation. If you're planning to switch from gas, proper loft insulation is the first step.
The standard approach is mineral wool laid between and over the joists in the loft. The recommended depth is 270mm - 100mm between the joists and 170mm laid at right angles across them. Installation typically takes half a day for a standard semi-detached house.
For a standard semi-detached house, professional installation costs around £300-500. Many households qualify for free or subsidised installation through the government's ECO4 scheme - particularly if you receive certain benefits or have a low energy efficiency rating (EPC D or below). Check eligibility at gov.uk/energy-company-obligation.
A typical semi-detached house with no loft insulation saves around £150-200 per year on energy bills after insulation. At current energy prices, that's a payback period of 2-3 years. The CO₂ saving is around 0.4-0.7 tonnes per year depending on your heating fuel.
Loft insulation is one of the few home energy improvements that competent DIYers can tackle themselves. However, professional installation is recommended for homes with limited loft access, older properties where the loft may contain asbestos, and any home where you're also planning a heat pump.
If your loft isn't insulated to 270mm, this is the first thing to do. It's cheap, effective, and makes every other home energy improvement more effective. If you qualify for ECO4, it may be free.
