For my case study of an international, certified Passive House, I have chosen the the Denby Dale Passive House in West Yorkshire in England. This Passive House was constructed by Green Building Store's construction division; Green Building Company for clients Geoff and Kate Tunstall. The Denby Dale Passive House is the first certified Passive House in the UK to be built using traditional cavity wall construction. The house has pioneered the combination of traditional construction methods with the German low energy Passive House design methodology.
The Denby Dale house is a 118m2 three-bed detached house with basic build costs of approximately €165,000. Not included in this initial cost were: garage, any external works, service connections, decorating, and any sun shading work.
The Tunstalls had initially wanted a rectangular shaped home but this design did not perform to the Passive House standards after modelling with Passivhaus Planning Package (PHPP) software. Instead a rectangular shape was chosen with the longest side facing south so as to achieve optimum solar gains. This new design met the desired 15 kWh/m2/annum level required for space heating. The clients also expressed there desire to have a conservatory in there new house. This is often a problem for passive houses as it is very hard to retain heat within conservatories, however this conservatory was incorporated into the building envelope as an integral solar space, with exterior brise soleil put in place to minimise overheating.
As heat retention was one of the primary aims of this development, the type of insulation used would be vital. In the end 100mm mineral wool batts were installed in the cavity three deep. This results in 300mm of insulation with each layer having a lambda value of 0.037. The outside of the cavity wall comprises of 100mm natural stone, with the inside comprising of 100mm block work. The Denby Dale house also uses a 500mm fibreglass quilt in the roof void and 225mm of high-performing poly foam insulation in the floor.
Cavity wall construction. www.building.co.uk
This house requires at least 90% less heating than the average UK house. The peak heating load for this house is calculated in PHPP as being 10W/m2 when the outside temperature is -10ºC. To allow for this space heating is provided by a conventional condensing gas combination boiler. Water heating is provided by solar panels, which were accquired under a local grant.
Points of interest:
- Walls in the Denby Dale House have a U value of 0.1 W/m²K.
- The Ecopassiv timber windows that were used in the build are triple glazed with low-emissivity coatings and argon fill and have a whole-window U-value of just under 0.8W/m2K (and glazing U-value of 0.6W/m2K)
The Denby Dale house overshot the airtightness requirement (0.6 air changes /hour @50Pa) by about 33% and also came in well under the space heating requirement of 15 kWh/m²/annum.