Dormont Park Passivhaus Project

 

Dormont Park exterior

Project lead
Jamie Carruthers, Dormont Estate, Dormont, Lockerbie, Dumfriesshire, DG11 1DJ

Building type, sector and stage
Domestic, private housing for rent, in use performance, Scotland

Keywords
Passivhaus, biomass, solar thermal, MVHR, zero carbon, affordable rent, timber frame

Time
At the beginning of a 2-year monitoring programme

Context
The houses are the first multi-unit development to Certified Passive House standard in Scotland and the first to be built by a private landlord for long term affordable rent in the UK.  The development in rural Dumfriesshire comprises 8 two-storey semi-detached houses – 4 two-bedroom and 4 three-bedroom – constructed from closed panel timber frame manufactured off site.  Cladding is a combination of larch and coloured render and dormers, external porches and chimneys are integrated into the design to ensure that the houses complement the local rural vernacular.
The houses are all designed on an east-west axis to maximise solar gain from the south facing elevations and the semi-detached design also reduces heat loss through the party wall.  The inclusion of dormers and external porches is designed to cater for the additional insulation requirements to ensure the houses are cold bridge-free.

Dormont Park

Targets
Super insulating the building fabric has resulted in U-values of the constructed building fabric being:External wall U-value is 0.095W/m2K
Roof U-value is 0.118W/m2K
Ground floor U-value is 0.111W/m2K
Windows have a U-value of 0.74W/m2K

Air tightness test for every property achieved 0.6ac/h@50pa.  Paul MVHR units provide a heat recovery rate of 90%.  The systems are exceptionally quiet in operation and ensure a very healthy and comfortable internal environment.     The units are fitted with a post heater fed from the hot water tank to allow a heat boost if required.  As a result primary energy demand is less than 120kWh/m2/year
Domestic hot water for the houses is provided by solar thermal panels feeding a storage tank and supplemented by a log burning stove with back boiler.  A suitable wood burner had to be specified which provided minimal heat to the room and also did not draw any air through the unit. The selected unit takes 90% of heat to the hot water tank and has a direct combustion air feed from outside.   CO2 emissions from this unit are 4g/kWh.

Performance
Tenants took occupation in July 2011 and their reaction has been overwhelmingly positive.  The knowledge that the houses will be comfortable with permanently low energy costs is more than enough to make up for finding out about the new and unusual systems.  Tenants need little encouragement to monitor their energy use and share information so that they can change the way they use their systems and reduce energy use still further. 

Conclusion
The buildings are being evaluated by the Mackintosh Environmental Architecture Research Unit (MEARU, contact t.sharpe@gsa.ac.uk). The study will examine if the targets identified at the design and certification stage are being met and how close to ‘zero-carbon' this development has come.  It will look at the affects of occupancy on the building performance, and evaluate the environmental performance of the houses and the effects this has on occupants.