Energy performance certificate and insulation

In short: The energy performance certificate describes how much energy a building needs. Insulation reduces heat loss through roof, walls, windows and cellar.

In more detail: When selling or re-letting, the owner must present the certificate. It is a comparison value, not a guarantee of actual heating costs.

In Depth

• Demand certificate: Calculated from building parts and heating, independent of residents’ behaviour. Consumption certificate: From the bills of the last three years, hence dependent on usage behaviour.
• Efficiency classes: A+ (very economical) to H (very high). Figures for final energy demand in kWh per square metre and year.
• Validity: Ten years. Issuers should be qualified; pure online certificates without data from the house should be viewed critically.
• Heat loss: Roughly the largest shares go through outer walls and roof, plus windows, cellar ceiling and ventilation. A building with high loss needs much heating power.
• U-value: Measure of heat transfer through a building part. The smaller, the better insulated.
• Measures: Insulate the top-floor ceiling or roof (often inexpensive), insulate the cellar ceiling, façade insulation, replace windows, insulate heating pipes. Plan the order wisely so heating and building match.
• Moisture: Insulation changes humidity and thermal bridges. Specialist planning avoids mould, see ventilation and mould.
• Subsidies and duties: There are funding programmes, as well as duties on renovation and heating replacement. Both change, check current rules.

See also: reducing heating costs, heat pump