Loft Insulation Payback & Savings Calculator
Calculate how much loft insulation saves on heating bills and when it pays back. Find out if you qualify for free insulation through government grants.
Loft Insulation Guide
How Much Does Loft Insulation Save?
Up to 25% of heat is lost through an uninsulated roof. The Energy Saving Trust estimates loft insulation saves: detached house: £320-480/year (old uninsulated) or £50-100/year (boosting from 100mm to 270mm). Semi-detached: £200-350/year (uninsulated) or £30-60/year (top-up). These are average figures — actual savings depend on how often the heating is on, the local climate, and the house's other insulation and draught-proofing. Well-insulated walls and floors make roof insulation even more valua
DIY vs Professional Installation
Loft insulation is one of the easier DIY home improvements. Materials: mineral wool roll (Knauf Earthwool, Rockwool) is available from builders' merchants. For 270mm: lay two layers of 100mm rolls at right angles (better for bridges across joists). Protective gear: dust mask (P3 FFP3), safety goggles, gloves, and old clothing — mineral fibres are irritating. Lay across the ceiling joists, not between them (this would leave cold bridges). Watch for: water tanks (insulate around but not under — fr
Government Grants — ECO4 and GBIS
ECO4 (Energy Company Obligation): energy companies are obligated to offer free insulation to lower-income households. Eligibility: receiving certain benefits (Universal Credit, Pension Credit, Housing Benefit, Child Benefit on low income) or EPC rating D-G with income below threshold. Great British Insulation Scheme (GBIS): broader eligibility than ECO4, covering council tax band A-D properties in England with EPC below D or EPC E-G regardless of council tax band. Local Authority Delivery and HU
Loft Conversion Considerations
If the loft may be converted in future: insulate the rafters (slope) rather than the ceiling joists — this keeps the loft space warm. Rafter insulation requires: rigid foam boards between rafters plus a 50mm ventilation gap at the top. Alternatively, spray foam insulation (not recommended — difficult to remove, may affect mortgage and sale). Most loft conversions require minimum 100mm mineral wool between rafters plus a rigid board or plasterboard — total thermal performance should achieve U-val
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