Passivhaus in Berkshire: not only a simple box!

Located in the village of Chieveley in West Berkshire, this timber-clad Passive House stands out in the empty green fields of the surrounding area. The architect Tom Gresford of Gresford Architects practice based in London together with Mike Jacob of Truck Low Energy Building worked on the design and build of this 4-bedroom house.

Old Water Tower, Chieveley, Berkshire, UK. Design by Gresford Architects, 2015.

It is a great example of vernacular architecture inspired by the traditional timber-framed barns of Berkshire area. Realized with an external  vertical pattern of timber cladding which confers plasticity as well as games of shades and lights to the exterior distinctive appearance.

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Night view of Old Water Tower, Chieveley

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Six months, a relatively short time to deliver this passive house, of which the timber structure was entirely  produced in Ireland by the Irish Stalwart MBC timber frame company. The structure was raised in only two weeks which helped in keeping the costs down to the budget of 350,000 £. ‘That takes a huge amount of money out of the equation in terms of build time‘ Gresford states.

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The layout is mainly open space with very few doors. The ground floor is organized around two living spaces with the staircase and the hallway to connect them. The South West orientation of the living spaces is not optimal  for a Passive House and indeed created some issues with the over-sized heat loss area. This was worsen by the high heat loss form factor of 3.29. Nevertheless, this choice was motivated by the panoramic countryside view  that opened in the West, whereas the East overlooks the adjacent houses, therefore featuring small windows. External blinds are automatically deployed on the east, south and west elevations when internal temperatures reach 21 degrees, thus reducing the risk of overheating.

Old Water Tower, Chieveley, Berkshire, UK. Design by Gresford Architects, 2015.

Old Water Tower, Chieveley, Berkshire, UK. Design by Gresford Architects, 2015.

Due to the high form factor (above 3.0 is quite challenging to achieve Passive House standard) the envelope had to be particularly efficient, so for the walls 400 mm of EPS insulation were specified, roof featured 500 mm of EPS Platinum Springvale insulation between studs and the slab is insulated underneath with 400 mm EPS insulation. Although Ecobead EPS insulation is a recyclable material with an average thermal conductivity of 0.040 W/mK , it is not breathable, as generally all the foam insulation is. Using a breathable insulation like hemp or woodfibre to be posed within the timber studs structure could have resulted in a better performing fabric as per vapor and moisture control.  Additionally,  natural materials are more sustainable since they come from renewable sources and they carry no toxic elements embedded.

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Entrance to the house, Old Water Tower, Chieveley

The house is heated by a  conventional LPG boiler supplying a radiator per room, whether the ventilation is supplied by a Paul Novus MHRV system with 88.9 % efficiency. The MVHR ensures the indoor air quality of the house will be kept within optimal levels of humidity and CO2 percentage, supplying always fresh and clean air from the outside.

Overall the simple design together with bold choices in regards to the materials used, as per the interesting timber clad design and windows orientation, which does not follow  in full the convenient ‘thermal’ rules of the Passive House standard, confers to this project  a high architectural value. This project shows that PassivHaus rules or ‘attentions’ are not bare limitations to the architectural design, but can be adapted from case to case and when necessary the architect can prioritize some according to the specific design requirements.

As a matter of fact the building has been nominated for the South and South East RIBA award under the residential category, and it has been shortlisted for the Passive House Trust Award.

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Sources

The Old Water Tower shortlisted for Passive House Trust Award 2016

http://www.rinnovabili.it/greenbuilding/passivehouse-forma-fienile-876/

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