


さて公共建築にあんまり馴染みのない仕事人生人間の目に飛び込んできた古平町の庁舎建築その2です。
わたしたちのように一般木造住宅を基本にした分野で加速度的に取り組まれてきた「省エネ化」手法としての高断熱高気密化や、自然エネルギー活用などはRC建築の分野ではあまり取り組まれてこなかった。
ZEH基準などの一般化は一般木造住宅での住宅性能革命が運動的なコアを形成してきた。その運動は寒冷地・北海道で「あたたかい暮らし」を希求する庶民が求め、先端的な研究者や建築実務者、その需要に正対した地域公共団体という官・学・民が「協働」してきて普遍化してきたもの。その成果がやがて全国に拡散してきた。
一方のRC建築では北海道ですらコスト面から、マンション建築でもいわゆる「外断熱」手法などへの取り組みが遅れてきた流れがある。戸建て住宅での実践がはるかに先行してきた。そういう性能進化の動きの中から生み出された手法、窓の性能強化=複層化などがリフォームで部分的に広がってきた程度。それがようやく新築段階でもこの古平町新庁舎のように、RC外断熱を初めとする手法が実践されるようになってきた。北国の公共建築として必然的な性能向上といえるけれど、まだまだ都市部のマンション建築などでは導入されていない。その要因はコストアップが大きい。ZEB化(Net Zero Energy Building〜ネット・ゼロ・エネルギー・ビル〜の略称で、建物のエネルギー消費量を正味でゼロにすることを目指した建築物)の最大の障害となっている。
その障害を地方公共団体の建築工事において克服したいと考えたとき、設計と建設の「分離発注」が常識とされてきた「専兼(せんけん)の壁」を取り払うことを、この古平町の新庁舎では採択した。ここでは建設会社の設計部門と建設部門が1社でワンストップ的に機能して、性能向上とデザイン性のレベルアップを実現した。戸建て住宅では一般化している手法が公共建築で実現したということ。
木立ちのようなRC壁柱に組み込んだ輻射暖冷房。これは外断熱で室内側は北海道産カラマツを型枠として使用したコンクリート打ち放し。暖冷房機能も兼ねる。地中熱ヒートポンプによる温冷水を壁柱内に流し室内側の壁を温めたり冷やしたりする「輻射暖冷房」。さらに南東と南西面の開口部には、太陽光発電ガラスを採用し外が見える状態で発電する。住宅レベルの性能技術革新がこうして実現されている。
久しぶりに公共建築で「面白い」と感じさせられていた次第。
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English version⬇
Cost Reduction by “Lump-sum Ordering” of Design and Construction Furuhei-cho New Town Hall Part-2]
The “performance improvement” that detached houses have led by far is now beginning to be realized in RC construction as a result of cost reductions. ...
This is the second building in the town of Kodaira, which caught the eye of a person whose work life is not very familiar with public buildings.
The “energy saving” methods of high thermal insulation, high airtightness, and the use of natural energy, which have been pursued at an accelerated pace in the field of general wooden houses, such as ours, have not been pursued so much in the field of RC buildings.
The generalization of the ZEH standard and other standards has formed the core of a movement to revolutionize housing performance in general wooden houses. This movement has been universalized through the “collaboration” of the public, academic, and private sectors, including advanced researchers, construction practitioners, and local public organizations that have responded to the demand of the general public for “warm living” in the cold region of Hokkaido. The results of these efforts eventually spread throughout Japan.
On the other hand, even in Hokkaido, there has been a trend of delayed efforts in RC construction, even in condominium construction, due to cost considerations, such as so-called “exterior insulation” methods. The practice in detached houses has been far ahead. The methods developed in this trend of performance evolution, such as window performance enhancement (i.e., multi-layered windows), have only partially spread to remodeling. Finally, methods such as RC exterior insulation are now being used in new construction, as in the case of the new town hall in Kodaira. Although this is an inevitable performance improvement for public buildings in northern Japan, it has not yet been introduced in condominiums in urban areas. The main reason for this is the cost increase, which is the biggest obstacle to ZEB (Net Zero Energy Building, a building that aims to reduce the net energy consumption of a building to zero).
In an attempt to overcome this obstacle in building construction by local governments, the Furuhira Town Hall was designed to break down the “Senken Wall,” which had been the common practice of separating the design and construction of a building. Here, the design and construction divisions of the construction company functioned as a one-stop shop to improve performance and design. This means that a method that has become common in detached houses has been realized in public buildings.
Radiant heating and cooling incorporated into RC wall columns like a grove of trees. The interior is insulated externally with fair-faced concrete using Hokkaido larch as the formwork. It also serves as a heating and cooling system. Geothermal heat pumps are used to heat and cool the walls on the interior side of the building by pouring hot and cold water into the wall columns. In addition, the openings on the southeast and southwest sides of the house are fitted with photovoltaic glass to generate electricity while allowing the outside to be seen. This is how the performance innovation at the residential level is realized.
For the first time in a long time, I was impressed by a public building that I found interesting.
Notice
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