Passive House in Somerset

This rural Passive House has been designed by architect Graham Bizley and his wife Emily and is one of those architectures where the relationships with the locus amoenus, in this case the valley of Somerset, has been carefully thought through. The house has won the RIBA South West Award 2015 for its sustainability feature and its architectural value.

The house is located on a slope therefore it is organised on two levels, although having just one floor on the higher part of the slope and two levels on the lowest one, so that no place in the house is underground.

The main construction material is timber, which has been used  for both the softwood timber framed structure, the external cladding in green oaks and the oak internal lyning. There is a loggia facing southwest which is very peculiar, built of oak posts and resembling the trees of the surrounding woods. It works as a shading system to the south exposed rooms avoiding overheating risks and providing an external contempling and usable space for the summer months.

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Passive House in Somerset, UK

 

The fabric of the building has been specially pushed over to reach very high standards of thermal efficiency. The ground floor features 40 mm woodfibre insulation on the reinforced concrete slab and on 250 mm EPC insulation achieving 0.12 W/m2K.

The pitched roof is composed by a metal roofing on the external side, than a ventilated cavity formed by softwood battens on a breather membrane, 356 mm Warmcell insulation blown within timber rafters, an airtight OSB board  and finally 50 mm hemp insulation between battens. The roof achieves an U-value equal to 0.11 W/m2.

Also for the walls Warm cell insulation (recycled loose cellulose), one of the greenest and cheapest materials on th market) has been used between studs and an OSB board as the airtightness layer.On the inner leaf there is a 50 mm service void with Hemp insulation, which ensures that the airtightness layer is protected.

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Warm cell insulation blown within the timber structure

In terms of services the building is  served by a 93% efficiency MVHR unit, which also supplies pre-heated air to the rooms. Due to the very performing fabric, the MVHR system together with a wood burner is the only source of heating in the house.

Here it is a  summary of the building performance:

  • Space heating demand (PHPP): 14KWh/m2/yr
  • Heat load (PHPP): 10 W/m2
  • Primary energy demand (PHPP):120 /k/wh/m2/yr
  • Airtightness at 50 Pascals 0.6 ACH

As a result the building meets the demanding Passive House standard successfully, even without being the conventional mono block house patio free and at the same time it is a charming and cozy home with high architectural value.

Sources:

Passive House+, issue 14, 2016

https://www.architecture.com/StirlingPrize/Awards2015/SouthWestWessex/DundonPassivhaus.aspx

http://www.prewettbizley.com/dundon-passivhaus.html

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