If provided, we calculate the total U-value of the existing component plus new insulation. Leave empty to assess the insulation layer only.
Energy rate per kWh from your bill (heating oil: price per litre ÷ 10)
Assumption, e.g. 0.9 for a condensing boiler; for a heat pump its seasonal performance factor
Optional – for the payback
Assumption 66 kKh/a (simplified heating-period method, average climate); differs by location
U-value
0.33W/(m²K)
0.33With 10 cm of insulation (λ = 0.035) your component reaches a U-value of 0.33 W/(m²K). The GModG maximum for External wall (0.24) is not met – that would need 14 cm.
Insulation needed per target
Calculation per DIN EN ISO 6946 including the surface resistances Rsi/Rse of the component. The GModG maximum values (Building Modernisation Act, until July 2026: GEG) apply to alterations of external components on residential buildings (Annex 7 to Section 36 GModG). Without the existing component, only the insulation layer is assessed – the real component then performs better. A certified energy consultant handles formal verification.
For the savings we need the U-value before (under “existing”), the area and your energy price.
Maximum values: Annex 7 no. 1a, 5a, 5c, 6a GModG (until 28 July 2026 GEG; renamed by BGBl. 2026 I No. 226, values unchanged). Savings: ΔU × area × degree hours ÷ efficiency.
Insulation Calculator by Rechnerzentrale(opens in a new tab)2026 values