Designing with a nautical theme can be a tricky business. But in the case of the Apelle house in Karis, in southern Finland, the reference is acceptable. By using locally sourced spruce in a small, 140 sq m home with no internal walls, Helsinki-based architect Marco Casagrande created a continuous, vessel-like home that he describes as 'sailing through the woods'. But the nautical comparison isn't limited to the design. In fact, the carpenters who were hired to build Apelle normally build boats, not buildings.

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The new construction, which was completed last year, was the result of careful studies Casagrande made in winter when the area was covered in snow. He aimed to create a home that would stay warm and comfortable in the bitter Finnish winter, but also open to nature in the idyllic summers. The home's four large doors can remain open to let air inside, and multiple shaded patios give the residents spaces to dine and relax outdoors.

The site previously housed a utilitarian shack, and Casagrande believes the former owners of the land were discouraged from building any normal-sized structure, as that would require removing the existing bedrock. Instead, the designer - who has experience building sustainable, humanist architecture and won the European Prize for architecture last September - wanted to create a harmonious connection with nature that would disrupt the landscape as little as possible. The resulting structure, perched on a ridge, is the architect's contemporary take on the traditional tupa, a multifunctional home allowing for a variety of activities.

But keeping the space warm and efficient in the winter dictated most of design. Geothermal pipes provide the home's primary heat, and are augmented by two wood-burning fireplaces: a black-brick one in the front that extends to become a bench that draws warmth from its hearth; and a second-akin to a Swedish stove-near the main sleeping area in the rear. Portholes that face a desk allow direct light into the living area, as do skylights and a glass wall at the entrance that faces west to soak in the setting sun. 'When the sun is circulating, it comes through that skylight and illuminates different parts of the house at different times of the day,' says Casagrande 'and that changing of light inside the house creates such a good feeling.'