A Passivhaus in a challenging setting
This project began when the clients originally approached RDA with a vision to build a contemporary, energy efficient two to three-bedroom home on a challenging site in Chiswick. Early in the design process, RDA introduced the client to Passivhaus and from there on achieving Passivhaus certification became one of the driving forces for the project.
Due to the sensitive location, a creative design was required to obtain planning permission. One of the major challenges was proving to the community and local council that the house would fit into its surroundings, a leafy Edwardian street.
See also: Down to Earth: Geothermal Heating
To overcome these issues RDA designed a sunken house, placing 60 percent of the building’s volume underground. This allowed RDA to satisfy the brief provided by the client whilst making the building appear smaller and therefore less prominent from street level. Sinking the house also created a private courtyard space for the two bedrooms on the lower level. London stock brick slips were used on the ground floor to match the local vernacular and a living wall was created on the first floor to soften the building’s appearance. The intention is that as the home ages the plants will grow and cause the first floor to disappear, further reducing the building’s prominence in its surrounding environment.
The house’s unashamedly modern interior is completed with exposed concrete walls, complementing the bespoke timber staircase and floors. The vast amounts of natural light brought into the house opens the space whilst the solar gain, achieved along with high levels of insulation, mean that minimal heating input is required. This house proves that Passivhaus certification can be achieved on a tight budget and without compromising high quality bespoke design.
A protected lime tree posed a problem for this sustainable build
Lime Tree Passivhaus is a small retirement bungalow on a garden plot for private clients and the design is a response to a number of key constraints, including the tight site and the presence of a protected lime tree.
The curved form of the dwelling, centred around the lime tree, allows the building to make the best use of the site and positions the tree as the central focus for both the building and the garden. The tree also serves to provide summer shading to the southwest elevation, ensuring an additional control against overheating. The curved monopitch roof contains an extra wide gutter and leaf protection to ensure that leaf fall doesn’t become a problem.
The tall ‘exterior’ of the curve is constructed in brick to match the context of the adjacent development, and to provide a strong shelter to the private side of the building, which in turn is clad in vertical larch timber boarding to reflect the arboreal nature of the garden. The curve finishes with a south-facing gable fully glazed to illuminate the sitting room, with large overhangs and flank walls to offer protection against overheating.
The building is constructed off a reinforced concrete raft supported on mini piles, carefully threaded past remaining archaeology, to support a traditional cavity wall construction and radial ‘I’ beam timber rafters. The insulation is provided by blown EPS platinum beads in both the walls and the roof, whilst the floor has 200mm of PIR insulation supporting a floating finish.
To see these and other case studies visit RDA Architects.
