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special report: housing
Architects impression of the site scheme
Evolving design
Norfolk-based Parsons & Whittley architects employed Passivhaus principles in the design of what is set to be the UK’s first rural affordable housing scheme to gain Passivhaus certification in Wimbish, Essex.
A
14 dwelling Hastoe Housing Association development in the village of Wimbish, Essex, at first looks like many other small
schemes of its type – but take a closer look at the design and detailing and it becomes clear that this could be a blueprint for such developments in years to come. The green-field scheme is being built under the
exception site policy to address local housing needs with funding from the Homes and Communities Agency and investment from Hastoe. Besides providing much needed affordable homes for a rural community the scheme is aiming for high levels of sustainability in order to address fuel poverty and climate change concerns. The houses, a mixture of homes for rent and shared ownership, are designed to be super energy efficient, comply- ing with Passivhaus principles and Level 4 of the Code for Sustainable Homes.
Passivhaus standard buildings retain heat
created within the dwelling as well as from passive solar gain, eliminating the need for central heating and reducing fuel costs. The standard requires very high levels of insulation (in order to meet U-values of below 0.15 W/m2
K for walls,
roof and floor), a design that makes the most of solar energy, and superb sealing throughout. Promoted by the Passivhaus Institute in
Darmstadt, Germany, there are around 25,000 Passivhaus buildings worldwide, the majority of them in Germany and Austria. The approach is growing in popularity in the UK as developers strive to meet zero carbon targets. Passivhaus stan-
raising the bar on materials performance in order to meet required elemental values and air tight- ness demands. Parsons & Whittley’s design for the develop-
ment, which is being built by Bramall Construction and assessed against Passivhaus standards by Inbuilt, is simple without unnecessary steps and staggers that would add to the heat loss area and complicate design and construction. A number of construction options were evalu-
dards were originally developed against European norms where floor areas tend to be larger. Adapting the standards for affordable housing in the UK where floor areas are smaller due to cost and space pressures means careful considera- tion must be given to design. It can also mean
‘The design for the development is simple, without unnecessary steps and staggers that would add to the heat loss area’
ated before adopting 190mm solid aircrete exter- nal walls wrapped externally in 285mm of rendered insulation. With extruded polystyrene insulation running under the reinforced concrete ground floor slab, and conven- tional
standard
trussed rafter roofs supporting 500mm Crown Loft Roll, the
construction details have been kept simple and effective meaning they can easily be replicated. Key to effective insulation was the use of a new blue extruded polystyrene foam insulation, which
CGI of the passivhaus flats
Wimbish Passivhaus under construction
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