House Z, designed by Benoit Rotteleur Architecte, transforms a 1980s house in Yerres, France, whose original layout reflected the domestic conventions of the period. Its semi-subterranean ground floor accommodated the garage and boiler room, living spaces occupied a raised level, and bedrooms were located within the attic. An extension added in the early 2000s had deteriorated significantly, prompting the owners to consider replacing the entire house. Instead, the architect proposed retaining the original structure and demolishing only the defective addition.
The renovation preserved the building's structural framework while substantially reworking its envelope, circulation, and internal organisation. The damaged extension was replaced with a timber-framed structure, while the roof was reconstructed to accommodate an additional floor with more space and natural light. By retaining the existing structure, the project avoided the material consumption and demolition waste associated with complete replacement.
Reorganising space and circulation
The renovation transforms the formerly compartmentalised house into a connected three-level dwelling. The entrance was relocated to the former garage, where the floor was lowered to increase ceiling height. A new concrete staircase connects the entrance directly to the principal living areas. The main living space extends from north to south, establishing views towards both the valley and the garden. Changes in level and spatial volume distinguish the living room, library, piano area, dining room, and kitchen without requiring extensive partitions.
A bow-window-style kitchen opens towards the garden, while full-height windows in the upper-floor bedrooms bring daylight into spaces previously constrained by the attic geometry. Functions that do not require thermal conditioning, including the garage, were moved outside the main insulated volume. This allows the thermal envelope to enclose primarily occupied spaces, improving the efficiency of heating and ventilation.
A continuous thermal envelope
Energy performance was central to the renovation. The existing walls were upgraded with external insulation, creating a thicker building envelope designed to minimise thermal bridges. The reconstructed roof and lower floor were also insulated, establishing continuity across the principal building surfaces. The replacement extension incorporates high-performance triple-glazed windows, limiting heat transfer while maintaining visual connections with the garden. Together, these measures reduce heat loss through the building fabric and lower the energy required to maintain comfortable indoor temperatures.
Passive solar control and ventilation
The house combines improved insulation with strategies that respond to seasonal conditions. On the south-facing façade, adjustable shutters regulate solar exposure, limiting unwanted heat gains during summer while allowing beneficial sunlight to enter during winter. The redesigned layout also provides views and openings on opposing sides of the house. A skylight positioned above the staircase supports stack-effect ventilation, allowing accumulated warm air to escape during summer. These passive measures help moderate indoor temperatures and reduce reliance on mechanical conditioning.
Efficient systems and renewable energy
A dual-flow mechanical ventilation system provides controlled air exchange while limiting ventilation-related heat losses. It operates alongside a central wood-burning stove, which contributes to space heating. Photovoltaic panels installed on the relocated garage roof generate renewable electricity. According to the project description, their output offsets the house's electricity consumption, although generation figures and annual demand are not provided.
