House in Hieidaira

House in Hieidaira, Otsu City, Shiga Prefecture, Japan by Thomas Daniell Architects, 2009

The following text and images are courtesy Thomas Daniell.

This is a single-family house designed for a lush natural setting in a new subdivision in the mountains above Kyoto. The site slopes away to the north, facing onto a National Park, with a view across a forest toward Mount Hiei (the most sacred mountain in Japanese Buddhism).

In compliance with new building regulations that mandate orthogonal walls and gabled roofs, the house takes the form of a nagaya (traditional row house): a linear sequence of rooms contained in a long, narrow volume aligned perpendicular to the street. The house expands in section to follow the slope: single-story at the street fa├žade, expanding to two stories at the rear of the site. This allows the gabled roof shape to define the interior spaces rather than simply sit on top of them. The bedrooms are half buried, whereas the living area is oriented toward the mountains.

The historical nagaya type is a response to the narrow, deep sites in congested inner-city Kyoto, with little or no space between buildings, but in this semi-rural location the lot has been divided in half longitudinally, with building and garden set parallel and having approximately the same width and footprint. The rooms are arranged as a band running along the western edge of the site, enabling natural light penetration into each room. The location of the building gives maximum separation from the neighbor to the east, and hence maximum sunlight in the garden area that remains.

The overall nagaya form remains as abstract as possible, made entirely from bare concrete. The roof has no cladding or surface membrane (an invisible waterproofing compound has been applied to the exposed slab) and there are no projecting eaves, making the house volume akin to something sliced from a block of tofu. There are no drains, downspouts, or gutters -- or more precisely, the entire roof plane has been subtly shaped to become an enormous rainwater channel. The roof perimeter slopes gently upwards, creating subtle parapets that prevent water from falling down the long walls, channeling it all to the building’s north and south ends where it may fall freely to the ground.

This area can receive heavy snow in winter, and so long-term durability and insulation was a primary concern for the clients. All the windows are double-glazed. With the exception of the storeroom (adjacent to the parking) and the sunroom (adjacent to the entry hall), all the exterior walls are insulated. They have been lined with 30mm-thick polystyrene foam spray, then finished with painted plasterboard. The roof and floor slabs have been lined with 50mm-thick expanded polystyrene sheets. The sunroom has been left in exposed concrete because it is intended as a semi-outdoor space, used as a greenhouse. Oriented to the southeast, it receives a great deal of direct sunlight through the glass walls and roof, and the exposed concrete wall visible inside acts as a heat sink that helps to warm the house at night.