The Peterborough EnviroCluster Retrofit Project was a Technology Strategy Board funded initiative to find new innovations and techniques to make social housing more energy efficient. Led by the EnviroCluster (UK CEED) and Peterborough City Council, a consortium of partners was formed which successfully raised £170k in funding to design and retrofit an end-terrace property in Peterborough.

The original proposal was to create a new envelope around the existing building by externally insulating to achieve higher U values for both the external walls and roof. Some 200mm of rigid insulation board was to be added to the whole of the front and side elevations, while the rear was to have 100mm of external insulation. The rear, which is south facing, was originally proposed to have a solar capture wall in addition to the 100mm. The idea for the external insulation was to minimise the impact to the internal faces of the wall and thus minimising the impact to the occupant.

The overall air tightness of the property was to be improved and the aim was to achieve passivhaus new build standard in the core fabric elements. Air management is through a heat exchange unit situated in the roof void and was planned to utilise the solar capture wall to pre heat air in the winter before circulating around the property. This was later designed out at the pre construction stage due to the budget cost and difficulties in quantifying the energy savings through SAP modelling. In the removal of this the external insulation was increased to 200mm to match the other elevations. Air ducts are incorporated into the wall insulation to pre-heat air entering the heat exchange unit in the loft; retaining some of the initial solar passive principles.

The roof was planned to be stripped of tiling, the trussed rafters strengthened, the roof externally insulated then retiled however the fasteners needed for this proposal proved elusive and the final solution included a cut timber roof over the top of the trussed rafters. The insulation was changed from a high decrement vapour open insulation to a low k value insulation vapour closed, so vapour open roof was replaced with vapour closed construction. Heat recovered from below the roof tiles is mixed with tempered fresh air in the loft space to feed the heat exchange unit and reduce the need to heat fresh air to the dwelling.

The property was retrofitted with low-mid performance double glazed PVCu windows with trickle vents, PVCu fascias and gable barge boards, and has retrofit guttering and down pipes. There is an internal bathroom, with artificial lighting and mechanical extraction. Mechanical extraction is also present to the kitchen. Windows illuminate the internal stairs on the west side along with the kitchen and one bedroom, and the lounge/dining room and 2 bedrooms on the east side. There is a high flush WC, bath and high flow taps, but no shower. The property is served by a retrofitted gas fired balanced flue boiler, with a redundant flue closed off but not insulated, and small radiators with TRVs located on internal walls. There is a large ground floor walk-in store, and 3 other cupboards provide potential for services.

Finally, renewable energy was proposed to provide water heating, with solar photovoltaic panels installed to reduce the amount used from the national grid.

With the exception of the solar capture wall the overall design principles remained the same through the build, however there were certain details that were altered in order to achieve the design.