Village of Freshwater, Isle of Wight. A scheme for 28 affordable homes has been designed and built to meet Passivhaus standard.
Initially the target was not to achieve such a demanding standard. Andrea Hulmes, manager of the Southern Housing Group comments: “We did not set out initially with the intention of developing Passivhaus, but like others across the industry, the Group was considering how to respond to the zero carbon Agenda, and so we looked at the fabric first approach..”.
The design of the scheme was assigned to the Architecture practice ‘PCKO Architects‘ and it included a courtyard layout, which produced high external wall surfaces, therefore more heat losses. Since this was limiting the feasibility for a PH building, the architects in conjunction with the passive house consultants decided to review the drawings and making them more suitable to achieve the standards without compromising the vision for the site.
The houses were also originally intended to be terraced houses, but eventually they turned into semi-detached houses. All the houses are 1 bed self contained units with the living space being a flexible room due to a folding partition for the creation of an optional guest bed. Flexibility is one of the key concept of this development, designed to create a sustainable and strong community.
The homes are built with masonry walls using H+H thin joint system and combining aircrete blocks with Celfix thin-joint mortar. This system allowed to build the houses faster. Additionally, instead of having a gap between the blocks of 10 mm, this was reduced to 2 mm in order to reduce air leakages throughout the fabric. David Harris, director of Stoneham Construction says that the bricklayers were instructed to cut the blockworks with millimetrical precision. This allowed also the homes to successfully achieve the 0.6 ach of airtightness required by the Passivhaus standard.The external solid walls are insulated externally with phenolic insulation boards and white render as finishing. Internally, the external walls have a parge coat followed by a service void and a plasterboard. This provides a robust solution as it allows for a service space without compromising the thermal performance of the walls.
Overall the success of this development is mainly due to the great communication between its PH consultants, architects and contractor. This allowed the different teams to work together and discuss and review design options from the initial stages, with the common objective to get the best and more efficient solution without compromising architectural aspects of the design.
fc&a Future Constructor and Architect, issue 73, March 16