Behind the scenes at Slip House
Footprint tours Carl Turner Architects’ Brixton house, designed to CSH Level 5
Footprint visited Slip House as part of Open-City’s recent Green Sky Thinking programme. The house occupies one of four empty plots in a Victorian terrace in Brixton, south London. Designed by Carl Turner Architects as the architect’s own home and studio, the 192m2 house is proposed as an adaptable prototype for contemporary terraced housing. Planks of translucent glass by Linit clad the exterior transmitting light to the interior without compromising privacy. Slip House is also a vehicle for the practice’s in-house research into sustainable design and incorporates an innovative PV-T array (joint PV and solar thermal) connected with a ground source heat pump.
A tour of the house with a group of 15+ other attendees was followed by a presentation of detailed technical and environmental data.
The building is comprised of three slipped orthogonal boxes which break up the bulk of the building and give it a sculptural quality. A steel frame structure allows an open plan and means that the organisation of the space can be easily transformed at a later date if required. The cantilevered form of the building enables maximum levels of solar radiation to be harnessed during the winter, whilst avoiding excess solar heat in summer. On the day we visited, the outdoor temperature was 14°C, while indoors it was 22°C with no heating.
Organised on four levels, the ground floor houses the office and kitchen, with the bedrooms above and living space on top. Outside the living area, a 20 m2 green roof houses a rooflight. The roof terrace offers an amazing 360° of London view whilst also acting as a platform for renewable technologies. A PV-T array system by Volther generates electricity for the ground source heat pump and for domestic water heating. The energy generated from solar radiation powers the ground source heat pump which is integrated in the pile foundations.
- PV-T for generating both electricity and hot water
- PV system electricity output of 1,147 kWh/year
- Solar thermal water heating output of 2,253 kWh/year
- Ground Source Heat pump (GSHP) integrated into pile foundations and connected to an underfloor heating system
Other sustainable features are:
- A 2,700L capacity tank for rainwater collection helping to reach the target of 80L/person/day water consumption
- 92% efficient MVHR
During the presentation, Carl stated that ‘without an airtight building, renewables would have little effect, highlighting the importance of the envelope’s airtightness within the design. He explains the house uses an Intello Plus airtightness membrane (available from the Green Building Store in the UK) fitted continuously to all internal wall surfaces and taped very carefully to all ceilings, walls and floors. The floors and roofs are inherently airtight as they have an in-situ concrete topping, sealing any gaps. The building is then lined throughout with a metal stud system spanning floor to ceiling, within which all the services are run. There are NO services penetrations through the airtightness membrane. Insulation is also fitted in three discrete layers to minimise any gaps occurring through workmanship issues. All doors are also lift and slide, fully air sealed. Sheep’s wool insulation was initially considered, however, phenolic insulation, highly resistant to water vapour, was used in the external walls to reduce the risk of condensation.
Materials and U-Values
- Green Steps triple-glazed windows, with timber frames sourced from Latvian forests
- Precast concrete floor slabs (manufactured in Cornwall) for thermal mass
- Externally insulated walls using phenolic insulation
- Walls U = 0.11 W/m2K
- Floors U = 0.11 W/m2K
- Roofs U = 0.09 W/m2K
- Windows U = 0.8 W/m2K
- Air permeability target of 1.5 m3/h/m2@50Pa
The architect has gained a planning permission in the plot to the right of the house for another three storey low energy house.
Carl concluded the visit with a demonstration of Slip House’s smart meter. When he turned on the kettle, the smart meter instantly indicated increased energy consumption, a practical tool for controlling how much energy occupants use in a building.
Designed to meet CSH Level 5 (but not certified), Slip House shows what can be achieved when both passive design and active renewable technologies are thoughtfully incorporated into a design from the outset. A two year monitoring process is currently underway via an OWL device which sends electricty data to the architect’s laptop wirelessly. Internal and external max/min thermometers with data storage will be installed shortly.