豪雪地の中心街に建つ住宅。既存の店舗を残して住宅のみを建て直したが、構造遡及を避けるため2つを離し、雪除けの庇付き路地でつないだ。
住宅の出発点は、冬の暗い室内風景だった。冬が明けるまで、あらかじめ雪の多少は分からないから、建て替え前の家では最大3mの積雪に備え、12月から4月まで1階の窓を雪囲い板で覆い、自然光から閉ざされた生活を送っていた。
施主は、両親に配慮して1階主体の生活を希望したが、普通のつくりでは冬は光から閉ざされてしまう。解法として、落雪のために勾配を付けた屋根の小屋裏をロフトに利用し、積雪より高いロフトの高窓から入れた自然光が、ロフト床に設けた開口部経由で1階各室に届くようにした。光を入れる大きな窓は冬の厳しい地域には不釣り合いだが、4重の空気層を設けることで、断熱性能を高めている。そうやって実現されたロフトと開口部から、家族のつながり方や、サステナブルな家の運用が逆に喚起されることとなった。
暗くなると、ロフトの開口部から各室の灯りが洩れて来る。全艶の塗装で仕上げた空のような2階天井にその灯りがぼんやりと映り、家族の気配が間接的にロフトで混ざり合う。「共有スペース＋個室の住宅」とも、「ワンルーム型の住宅」とも異なる、ぼんやりとしたコミュニケーションが、家族の新しい距離感をつくることになる。
ロフトは、物を置く現実的なスペースでもあり、物が語る、時間のうえでの家族の気配も、今を生きる家族の気配に重なって行く。
サステナビリティへの配慮
（1）冬季の自然光
ロフト高窓からロフトの開口部経由で、1階に自然光が落ちる。
高窓は大面積だが、ペアガラス内側に4重の中空層＋空気層を確保し、熱損失を防ぎ、断熱性能を上げた。自然光は窓面で拡散され、耐力壁を兼ねた鏡の壁でさらに増幅。それらの効果で、日差しの弱い冬季の昼間でも、1階の各室は人工照明なしに十分な照度を確保した。
（2）20年間のエネルギーコストの総額
冷暖房、給湯、屋根融雪のシステムを選定するにあたり、さまざまな熱源と形式の機種の、20年間にわたるイニシャル、ランニング、点検、交換コストを算出。ランニングコスト以外を含めたのは、それらも生産、運搬のエネルギー消費を発生し、サステナビリティに関わるからである。
数十通りの中から、20年間の総額のもっとも安い組み合わせとして、電気式空調の床下設置による冷暖房、一般型ガス給湯器による給湯、ガス給湯による温水循環パネル式の屋根融雪を選定した。
（3）省エネに配慮した空調システム
1階床下に電気式空調を設置。床下を空調のエアチャンバーとして利用。
床ガラリから出た空気が、室内循環後、トイレおよびロフトの吸込口から吸込まれ、ロスナイ経由で空調機に戻る。その繰り返しで、1時間ほどで一棟全体の室内空気がほぼ同温で安定する。
省エネ循環に移行した際、温度低下が起こらぬように、家全体を断熱材で魔法瓶のように覆った。1階床下は、外断熱＋躯体内側に断熱材を施し、それは外周部以外の内部の基礎立上りにもおよぶ。
それらにより、コストを抑えながら家全体に温度差のない快適な状態をつくり出した。
（4）南面の外壁＋大きな世界とのつながり
家の一辺を斜めに切り取っている。東西の方位軸に合わせているため、正確に南面する。
建物に囲まれ、風景も開けず、冬は雪に囲まれる。そういう状況の中、方位軸を室内に持ち込み、外に広がる大きな世界を暗示させた。
晴れた日の南中時には日差しが壁面に垂直に落ち、時間の変化を意識する。冬の日中は明るさを最大限に取り入れられる方位ともなる。
（5）夏季の自然風
庭に面する南面と路地に面する北面に相対して窓を設け、かつ、路地空間の高さが煙突効果をもたらすことで、自然風の通りやすいつくりとした。
（6）耐震性能
中越地震で大きな被害のあった地域である。そういう経緯もあり、筋交いは必要壁量の2倍以上を確保し、さらに全壁面で構造材の上に構造用合板を直打ちしているため、耐力は2倍以上にアップしている。（石井大五）
A house living sustainably with a loft with large light windows in a heavy snowfall area
The house is located at the center of the city that belongs to one of the regions with the heaviest snow in Japan.
The old laundry factory was left on the site, and only the house was rebuilt. Due to the standard building act, it was prohibited to connect the old building with the newly-constructed building. So, both were separated and connected by a small alley with eaves to avoid snow.
The starting point of designing this house was the dark indoor scenery of winter. It is impossible to foresee the amount of snowfall until the winter ends. In the house before rebuilding, the windows on the ground floor were covered with the protection board against snow coverage of 3 meters at maximum from December until April, so the family had to pass the life closed from the natural light in the rooms on the ground floor.
The clients required that they spend their life mainly on the ground floor in consideration of the aged grandparents. But, in the ordinary form of a house, their life would be separated from the natural light. So, as a solution, we proposed a house with a loft. The attic space of the pitched roof for sliding the snow was utilized as a loft, and the natural light is introduced to the interior from the high side window higher than the accumulation of snow. The natural light reaches each room on the ground floor through the openings disposed on the floor of the loft. The large window for introducing the natural light is disproportionate in the region with a severe winter climate, but the high insulation efficiency was realized by installing a four-fold air layer.
The loft and the openings which were realized so evoked the new form of the family or the rise of sustainability.
“A new distance sense between the family”
The light of each room leaks from the openings on the loft floor as it becomes dark. It is vaguely reflected on the ceiling of the loft like the sky finished with high gloss paint, and the family’s sign is indirectly mixed in the loft. The house is different from “a house composed of common space and private room” and “a one-room type house” but creates a new distance sense between the family through indirect communication.
The loft is also a realistic space that places things, and the sign of the family on time overlaps with the sign of the actual family.
The loft is isolated from the space where the small children move around in consideration of the accident.
“Consideration of sustainability”
1. Natural light in the winter
The natural light falls to the ground floor from the high side window on the loft through the openings on the loft floor. The natural light diffuses through the translucent glass and the twin-polycarbonate plates and is amplified by the mirror walls that serve as the earthquake-resisting wall. Through those effects, each room on the ground floor has enabled to acquire enough illuminance without artificial lighting, even in the daytime of the winter when the natural light is weak.
2. Total sum of the energy cost for 20 years
We selected air conditioning, hot water supply, and the snow melting system on the roof based on the calculation of the initial cost, running cost, inspection cost, and exchange cost for 20 years for various systems of different sources of heat. The costs, except the running cost, were included since those generate the energy consumption of the production or the transportation and are related to sustainability. Among about 40 combinations, we selected the cheapest combination.
3. Air-conditioning System in consideration with energy-saving
The air-conditioning is installed underfloor, and the whole space under the floor is utilized as an air chamber. The air goes out from the floor grill and, after circulating the interior, then goes back to the air-conditioning machine. According to the repeat of the circulation, the air of the whole interior is stable at the same temperature in one hour.
The whole house and whole space under the floor are covered with high-performance insulation so that the temperature drop would not occur in the energy-saving circulation. Therefore, the comfortable state that the gap in temperature doesn’t exist in the whole house has been realized, refraining the cost.
4. Exterior wall facing to the South
One side of the house is cut obliquely and precisely faces the South. The house is surrounded by buildings and is closed by the snow in the winter. This side suggests the cardinal points and the big world that spreads out outside.
At the culmination of the day, when it is fine, sunlight makes a shadow that is perpendicular to the wall and is conscious of a change in time. In the daytime of the winter, it becomes the direction where brightness is brought to the maximum.
5. Natural wind in the summer
This region is one of the regions where the temperature in the summer is highest in Japan. By the effect of the window disposition on the South side, and the North side and the height difference of the alley bring the chimney effect, the natural wind passes easily.
6. Earthquake performance
This region suffered heavy earthquake damage. Therefore, the length of the wall where the braces were installed is more than twice the necessary quantity of wall. Furthermore, since, in all walls, the structural boards are nailed directly on the pillar, beams, studs, and braces, the proof stress rises more. In the loft, the earthquake-resisting walls are covered with mirrors to weaken the sense of oppression. (Daigo Ishii)
【長岡の住宅】
所在地：新潟県長岡市
用途：戸建住宅
クライアント：個人
竣工：2011年
設計：石井大五＋フューチャースケープ建築設計事務所
担当：石井大五
構造設計：南雲正一（匠設計）
設備設計：ZO設計室
協力：加藤弘行
施工：池田組
撮影：フューチャースケープ建築設計事務所、長谷川健太
工事種別：新築
構造：木造
規模：地上2階
延床面積：245.77m²
設計期間：2007.08-2009.06
施工期間：2009.08-2011.07
【House in Nagaoka】
Location: Nagaoka-shi, Niigata, Japan
Principal use: Residential
Client: Individual
Completion: 2011
Architects: Daigo Ishii + Future-scape Architects
Design team: Daigo Ishii
Structure engineer: Shoichi Nagumo / Takumi Design office
Equipment design: Zo Facility Design
Collaborator: Hiroyuki Kato
Contractor: Ikeda-gumi Construction Company
Photographs: Future-scape Architects, Kenta Hasegawa
Construction type: New building
Main structure: Wood
Building scale: 2 stories
Total floor area: 245.77m²
Design term: 2007.08-2009.06
Construction term: 2009.08-2011.07
