Back to Projects

Green Factory successfully gained planning permission for a new dwelling in Oxford that was to become the cities first Passivhaus (we hope - currently awaiting confirmation of certification!).

The first design for the challenging site was rejected at pre-planning meetings. This design would have lent itself better to the use of solar thermal and PV technology and the more regular structure would have meant Passivhaus standards would have been more easily achieved. However a more conventional design was approved by the planners and whilst the available space for the solar technology was reduced we were able to improve the fabric u-values meaning we were still able to meet Passivhaus criteria.

The construction phase was undertaken by Frank McKenna who went beyond the call of duty turning the designs into reality. The difficulties of building to Passivhaus standard - meeting the air-tightness requirements and often using unfamiliar materials and building technologies - are not to be underestimated and a builder prepared to meet the challenges is extremely valuable.

The sub and superstructure walls were constructed with Durisol recycled timber blocks with Celotex insulation and concrete core - this was separated from the footings concrete with Foamglas structural insulating blocks to prevent thermal bridging.

The interior face of the Durisol blocks were wet rendered to achieve air-tightness. The external face was treated with the Kooltherm K5 insulation and a polymer render. The Internorm triple glazed windows were supplied by Milena of Witney. The first floor was constructed from Eco-joists which allow for service runs. Monodraught supplied a sunpipe running from the roof to ground floor - whilst we were sceptical of the performance over that distance - the light supplied is more than adequate. Total Home Environment designed and installed the Genvex 185 Combi - an air source heat pump for DHW combined with the MVHR with duct heating. Bathrooms are warmed by electric underfloor heating - the MVHR transfers this heat to the rest of the house via the heat exchanger unit. Rainwater Harvesting was designed and supplied by and installed by Frank McKenna.

The heat requirement achieved for the house is 15kWh/m2/a and the air-tightness 0.6ACH@50Pa.