Loft Insulation Calculator

Loft Insulation Guide

Standard Depths

Current Building Regulations require 270mm of mineral wool insulation. Most pre-2003 homes have 100mm or less. Topping up from 100mm to 270mm typically saves £150–250/year in heating costs. Grants may be available through ECO4 or local authority schemes.

Types of Loft Insulation

Mineral wool (most common): laid between and over joists in two crossed layers. Blown fibre: better for awkward spaces, requires professional installation. Rigid foam boards: used in 'warm roof' conversions where the loft is used as living space. For standard cold loft storage, mineral wool rolls are the most cost-effective.

Savings vs Cost

A 200m² loft insulated to 270mm using DIY mineral wool costs approximately £300–500 in materials. Annual savings of £200 give a payback of under 2 years. This is one of the best value green home improvements available.

Energy Efficiency Priorities

Home energy improvements should be prioritised by payback period. Quickest payback: draught proofing (£50-200 cost, saves £60-100/year — under 2 years). Loft insulation (£300-500 DIY, saves £150-200/year — 2-3 years). Switching to LED lighting (under £100, saves £40-60/year — under 2 years). Longer payback: cavity wall insulation (3-5 years). New efficient boiler (5-10 years). Solar panels (7-15 years). Heat pump (10-25 years at current energy prices). For homes eligible for ECO4 funding, the pa