Gap House

London, England

Pitman Tozer Architects
www. pitmantozer. com

Placed improbably between a pair of historical listed buildings, the contemporary facade of Gap House is a mere 2.3 metres wide. This newly built, four bedroom family home is the winner of the 2009 R. I.B. A. Manser Medal.

Situated in a conservation area in West London, the challenging site was used by the practice as a case study in energy generation and conservation. As the plot was constrained, it was originally an alleyway and a rear garden, the considered use of space was vital to the creation of a functional dwelling.

The innovative design stacks three individual bedrooms in the narrowest section of the plot. These sleeping quarters are located on the street elevation. The natural light and ventilation to these rooms is directed and controlled by opening windows and louvered shutters.

The stucco rendered finish allows Gap House to blend seamlessly into the terraced street. However, the property’s distinctive fenestration, shutters and front door provide the new building with a deserved individual architectural identity (Fig. 2).

Bedrooms and bathrooms are accessed by a central stairwell, which also acts as a light shaft (Fig. 1). There is a gap between the stairs and the walls to enhance light transmission.

To the rear of the plot, the property is arranged as a series of cascading, projecting cubes, descending to a ground floor reception area. This space, accommodating the kitchen, dining area, lounge and study, merges with a light-filled, outdoor courtyard, (Figs. 3 to 9).

178 Gap House | London | England | Fig. 1 above | Fig. 2 right

Throughout the design and construction of Gap House, a primary goal was to reduce the running costs of the finished accommodation. The aspirational target was to cut energy consumption by 70% compared to a similar sized unit built to current building regulations.

Multiply strategies were employed to achieve this goal. Three, 50 metre deep bore holes were drilled below the rear courtyard to serve a 12 kW ground coupled heat pump. This technology provides all the heating and hot water requirements for the property, including under floor heating.

This strategy was coupled with high levels of insulation to the walls and roof (U value 0.15 W/ m2K). This factor, along with the passive solar gain, minimise the overall supplementary heating requirement.

In the summer months the stack effect of the central stairwell provides passive ventilation via the opening skylight (Fig. 6).

Water conservation was also targeted, with rainwater falling on the site being channelled and
collected for re-use in flushing the toilets. Wherever possible, naturally occurring, sustainable materials are used, for example, the internal walls and floors are insulated with lamb’s wool. A composite larch board is used for the stair structure, and timber window frames are made from sustainable spruce.

Following completion, the property achieved an “Exemplary” grade 4 rating under the Code for Sustainable Homes. Energy bills are estimated to be £500 to £800 per annum cheaper than similar sized properties in the Greater London Area.

The reception area is constructed at double height (Fig. 5, Fig. 6, Fig. 7). This provides the opportunity to bring daylight in from above the courtyard via horizontal and vertical windows (Fig 8, Fig. 9).

A study placed at mezzanine level completes the clever use of the building’s volume, providing a secluded haven above the open plan reception space (Fig. 7, Fig. 8).