How is insulation payback calculated?

Payback is calculated by dividing the installation cost by the annual energy saving. Annual saving = (old U-value - new U-value) x area x degree-days x 24 / 1000 x fuel cost / heating efficiency. Fuel price inflation accelerates the payback period over time.

What U-values should I aim for?

Current Building Regulations Part L targets: walls 0.18-0.26 W/m2K, roofs 0.11-0.16 W/m2K, floors 0.13-0.18 W/m2K, windows 1.2-1.4 W/m2K. Uninsulated solid walls can be 2.0+ W/m2K, and single glazing 5.0+ W/m2K, so the savings potential is significant.

Which insulation measure has the best payback?

Loft insulation has the best payback (1-3 years) due to low cost and large heat loss reduction. Cavity wall insulation (3-5 years) is next. Floor insulation (5-10 years) and external wall insulation (15-25 years) have longer paybacks but are still worthwhile over the lifetime of the property.

What are degree days?

Degree days measure how cold a heating season is. One degree day occurs for each degree the daily mean temperature is below the base temperature (15.5C). The UK average is approximately 2,100 degree days per year. Northern Scotland can reach 2,800+, while southern England may be 1,800.

Does insulation payback improve with fuel price inflation?

Yes. If fuel prices rise by 3% per year, the annual monetary saving increases each year, shortening the payback period. Over 20 years with 3% inflation, cumulative savings can be 40-50% higher than at static prices. This makes insulation an increasingly good investment.

TradeCalculator.co.uk

Insulation Payback Calculator

Calculate the payback period for insulation upgrades. Compare current vs improved U-values and see annual energy savings, costs, and carbon reduction.

Building Element

Wall, roof, floor, or windows

Element Area

Total area of element

Current U-Value

Before insulation

Improved U-Value

After insulation

Installation Cost

Total installed cost

Heating Fuel

Fuel Price

Gas 6.5p, elec 24.5p

How We Calculate This

This calculator compares heat loss through a building element before and after insulation upgrade, using degree-day methodology to estimate annual energy savings.