How can existing buildings be retrofitted?
Design of a certified Passivhaus building

It’s not just new buildings that can be certified as “passive buildings.” The process can be applied to older buildings if the economic analysis shows that the project is profitable—with an ROI of less than 20 years, for example. It would be pointless to attempt this renovation on a building facing due north and/or shaded by other buildings. There is another certification called EnerPHit that allows for the renovation of an older building if the following conditions can be met.

• The heating demand must be less than 25 kWh/m²/year.

• Primary energy demand must be less than 120 kWh/m²/year for all uses combined.

• The airtightness under a pressure difference of 50 Pa between the interior and exterior of the building (n50) must be less than 1.0 vol/h.

• On fewer than 10% of the days in a year may temperature peaks exceed...