Retrofitted into passive house flats

Retrofitting a charming old family house into two new, modern, Passive House standard flats

Type: Retrofitting into Passive House

Carried out: October 2009

Net area: 302 m2

Window system: Rationel ALDUS

Heating demand: 14 kWh/m2/year

The first of its kind

In order to both update the building and meet the Passive House standard, the house underwent a major transformation. Retrofitting to the required level of energy-efficiency proved to be an incredible challenge, since the original building was subject to numerous restrictions and limitations.

However, we proved that it could be done, and this project actually became one of Denmark’s first examples of retrofitting to Passive House standard.

An experienced team

One of the biggest challenges - made even larger when retrofitting - was the blower door test (an air leakage test), which we managed to pass first time. A lot of this success was down to the knowledge and expertise of both the project group and the building material suppliers, both of whom had worked on retrofitted Passive Houses in the past.

According to the architect, the retrofitting resulted in a 93% saving on the energy bill – since the villa's previous heating demand was 219 kWh/m2/year.

The redesign of the building included an increase of the window area on the southern façade to take in and store free heat from the sun, and the choice of pane, size and opening function of each window were carefully selected to optimise the building’s capacity to let in and store light and warmth.

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