Origin Housing took the bold step to redevelop a site that had long been a focus for antisocial activity. However, the development had to meet challenging criteria to provide flexible accommodation for the changing demands of the Harrow community. YOOP architects rose to this challenge and in the process designed a development that has become a model for Zero Carbon homes for Origin Housing.
Origin acquired the site with the intention of developing a mixed housing development, which would be flexible enough for extended families to live there, long-term.
However the land came with its own history and challenges. It was the site of the former Box Tree Public House, which had been empty since 2007, fallen into dereliction and become a beacon for anti-social activity, before being targeted by arsonists on a number of occasions. It was also in a highly visible corner position, in a residential area largely comprising detached and semi-detached owner-occupied properties.
Origin acquired the land in February 2011, and entered into the planning process, with YOOP managing community liaison in conjunction with Planning Consultant Richard Henley at Preston Bennett. A community engagement event was held, where the community expressed overwhelmingly positive support for a development on the site.
YOOP took the opportunity to introduce an idea that would address privacy and high density living. This was not just an aesthetic concern – although there are many social housing developments where the local community objects to the storage of bicycles, toys and other household items on balconies – and YOOP was keen to produce a design that dissipated any resentment from neighbours, as well as providing practical, usable amenity space for residents.
The YOOP design was a horseshoe shaped building, with a large continuous wrap-around screen wall to provide generous amenity space for residents. The screen wall is punctuated by large openings, which provide the private amenity space for the flats. The wraparound wall creates the distinct character of the building as well as providing spacious and private external leisure amenities that will not intrude on the relative quietness of the streets in the area.
The horseshoe circles around a secure communal garden, which was factored into the building design to take account of the likely demographic of Boxtree residents.
Origin Housing was extremely clear about the need for flexible accommodation which included meeting the needs of extended families. YOOP’s interpretation of this part of the brief was to focus on multi-generational living, which is not a common model for social housing in the UK.
YOOP’s design included a six bedroom flat, which is quite unique in London. Intended for an extended family, the flat has a layout that can easily be converted to two two-bedroom flats should the six-bedroom layout no longer be required. The six-bed flat includes private front terrace incorporated into the screen wall and private rear garden.
The outside space was also designed to be sympathetic for the older generation, who may not be mobile enough to socialise away from home, and the garden includes a lawn, a seating area and a vegetable patch to provide a focus for communal involvement for the development’s residents.
Privacy between dwellings was a concern for Origin, who wanted to alleviate the common complaint of noise between flats, which can cause tensions between neighbours and a high rate of resident dissatisfaction.
YOOP approached the design with this in mind and specified solid walls between dwellings, constructed from building materials with high thermal insulation properties to reduce sound transfer between flats.
YOOP was keen that the sense of space conferred by the balconies should continue inside the properties, and gave the rooms a ceiling height of 2.5m to ensure continuity between the inside and outside areas.
Origin’s priorities included reducing fuel poverty in the borough, and demonstrable energy efficiency for the development was a pre-requisite of the development going ahead.
YOOP recommended a heat retention strategy rather than investing in renewables, which require maintenance and upgrades that all add to residents’ fuel and service charge costs.
Toby Rollason, of the sustainability department at YOOP, was responsible for the Passivhaus approach taken in the Boxtree development. His primary interest lay in ensuring the building envelope would be as heat retentive as possible, and he used some innovative approaches to meet requirements in the Code for Sustainable Homes.
The choice of building material was his first concern, and he chose a single skin of recycled concrete block as the primary structure. This was then insulated externally and render finished with plaster finish inside for air tightness. This material, which has a high thermal mass, effectively absorbs, stores and reemits heat produced inside the building, so the walls act as storage heaters to equilibrate internal temperature.
YOOP chose electrical heating to reduce the lifetime costs of the building, and used the gains made by this choice of wall fabric to compensate for the penalty that electrical heating attracts. Electric heating is typically difficult to get through the Code for Sustainable Homes due to the electricity being regarded as producing more CO2 that natural gas.
Air-tightness was the final consideration in the heat-retentive design – given that most homes have the equivalent of a window open at all times, Toby worked closely with the contractors to ensure junctions between walls, ceilings and floors were as close to airtight as possible, and installed a mechanical ventilation and heat recovery system to extract heat from the exhaust air in this closed system, so recirculating the internal heat gains back into the system.
The net result of the design is a building that is so heat retentive that residents are only expected to turn on the heating in the coldest months of the year, if at all.
The cost of the Boxtree development was £1.8m. It contains 14 homes of mixed sizes, including four houses with private gardens and a six-bedroom flat and full wheelchair unit.
Architect Gordon Evans comments: “Reduced service costs for residents, who will benefit by low heating costs, and the relative stability of electricity prices compared to gas, produces a long-term social benefit, that will help ensure the social stability of the development and addresses fuel poverty head on.”
The scheme is now seen as a low cost model to achieving zero carbon, which is required by 2016. The model maximises all the simple things like fabric before moving to more complex ingredients like micro renewable technology.
The other over-arching aspect of the Boxtree model is that it addresses sustainability for the resident as well as the environment. The key issues of privacy, fuel poverty, noise and amenity space are all very important in making places sustainable and healthy to live. Gordon Evans adds: “This is the overall win at Boxtree, a healthy and sustainable place to live.”
YOOP architects worked in collaboration with Origin Housing on community liaison, and partnered with Sandwood Design & Build, which acted as the design and build contractor and specialist in delivering high quality sustainable construction techniques for the affordable housing market. Structural engineering was by Thomasons, building regulations by Butler & Young, landscape design by DCCLA and landscape delivery by Clews Landscape Architecture.
Origin Housing provides essential affordable housing, and care and support services to 5500 homes in north London and Hertfordshire, with the aim of improving communities and the lives of customers. Origin is a provider of mixed tenure and mixed-use development with a strong reputation for housing support and community development.
