Tono Mirai
Tono Mirai architects, Karuizawa/Nagano, Japan

Shell house – The language of the forest
In the centre of Japan, a small villa has alighted inThe house minimises its environmental impact

the forests of Nagano Prefecture – a self-contained

through the use of local FSC-certified wood, earth,house made of local wood and earth, constructed us-

human craftsmanship, and no petrochemical materi-ing traditional techniques and designed to meet con-als – materials such as plywood, laminated timber or

temporary environmental performance requirements.

gypsum plasterboard were not used.

The building is a product of the client’s request for awork of “architecture that is unusual, beautiful, andThe interiors are finished with locally sourced earth

does not make you feel old in time” as well as twoand wood. The earth plaster of the internal fac-primary conditions: the strict need to observe the re-es gently stretches in a continuous flow across thetreat line of the landscape regulations and to occupy

curved interior. By retracting the sliding sections of

no more than 20% of the 290 m² site.

the southeast window frontage, the interior extends
out onto the deck and into the forest beyond. TheTaking this as its starting point, the house presents

first floor takes the form of an open platform reacheda closed facade to the streets and waterway to thevia a curved stair with a bathroom at the rear con-north and west sides and an open south-facing front-

cealed behind a continuous wooden door.

age to the forest to receive light and heat from thesun. Its organic shape and open frontage help it “to-The house is designed according to passive designtally blend into the surrounding forest” to the southstandards. The external walls and roof have an av-and east.

erage heat transfer coefficient of UA = 0.49 W/m²K

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Shell house – The language of the forest

and the building has achieved a five-star S-rating

The building structure is designed around sevenfor the Japanese CASBEE Comprehensive Assess-curved beams born from the organic earth wall thatment System for Built Environment Efficiency. It un-

express the cycle of human life and of the cosmos.

dercuts the primary energy consumption standards

The two inscribed circles represent the correspond-in Japan by 11%. The earth wall is insulated withence of the two. The shell house is a work of archi-

180 mm of wool insulation with a thermal coefficient

tecture that resonates with human life and is born ofof U = 0.207 W/m²K.

and will return to the earth.

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Tono Mirai

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Shell house – The language of the forest

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Shell house – The language of the forest

Key dataArchitect:

Finishing materials
Tono Mirai architects / Tono Mirai

External roof & walls:

Asphalt shingles

www.tonomirai.com

Internal wall & ceiling: Locally sourced earth

nest@tonomirai.com

Floor:

Wood flooring and locallyContractor:

Terashima Construction Company

Structure:

TimberFireplace:	Rammed earth

Footprint:

37.80 m²

Window and doors:

Floor area:

58.04 m²

Site:

290.94 m²

Design:	October 2011 – April 2016
Construction:

April 2016 – July 2018

Photo and drawing credits
Photos of the completed building: © takeshi noguchi
Drawings, model and site photos: Tono Mirai architects

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sourced earth
Timber sliding door and window
panels made of aluminium andresin composite with double andtriple glazing.