→ First Victorian residential retrofit in the UK to be certified PassivHaus

→ Achieved remarkable airtightness (0.34 m3/m2 h @ 50 Pa on completion)

→ In-depth post-occupancy evaluation report
→ 83% less energy consuption than the ‘typical house’

→ The carbon emissions have been reduced from 70 kgCO2/m2/yr down to
20 kgCO2/m2/yr

This project was the first Victorian residential retrofit in the UK to be certified to the PassivHaus standard. It was part of an initiative to address the challenge of how to reduce carbon emissions in existing housing stock. The project was won through a government competition entered in collaboration with Octavia Housing, Eight Associates and Ryder Strategy. 

An 80 per cent carbon emission reduction was achieved through effective and innovative teamwork. The house has very low energy demand and the omission of the conventional gas energy source. The property is a typical mid-19th century Victorian terraced house, located in a conservation area. Built in 1840, the house was found to be in a very poor state of repair and in need of a significant upgrade.

The retrofit meant that heating energy demand requirements were reduced significantly with the implementation of PassivHaus principles. These involved the installation of a number of key features as well as the complete elimination of cold bridges within the structure and envelope. To satisfy both planning and PassivHaus the windows were a key design component which ultimately were designed and manufactured as an R&D project. Such windows didn’t exist at the time of the project so the decision was taken with the client to design and manufacture them as a ‘look-alike’ sash window, very close in external appearance to the original Victorian one but formed of a fixed top light and a bottom casement opening inwards with three perimeter seals.

Hot water is produced by means of three solar panels on the south facing roofscape. No central heating system or radiators were fitted and the house is not connected to the gas network. Additionally the project features an internal insulation strategy; a unit combining MVHR, an exhaust air heat pump and hot water storage and an underground labyrinth that tempers incoming ventilation air beneath the footprint of the house.

The project was part of a comparative monitoring programme looking at three Victorian terraced houses of similar layout and all located within metres of each other. It included this PassivHaus, a ‘Decent Home Plus’ house (50 mm internal wall insulation and double glazing) and a typical UK house (no insulation and single glazing). The post-occupancy evaluation report found that the demand in final energy for the PassivHaus was 63 kWh/m2/yr and 366 kWh/m2 /yr for the typical UK house. In other words, the PassivHaus consumed 83 per cent less final energy than the ‘typical house’. In addition, the final energy demand for the PassivHaus remained low and very consistent throughout the year while it increased sharply in the heating season for both the Decent Home Plus and the typical UK house.