Facilities planning to overcome the "hurdles of wooden construction" for a new era

What we will introduce today is a design project for Japan's first high-rise hybrid wooden hotel, which aims for the ultimate in local production and consumption, focusing on the use of building materials and ingredients from Hokkaido in everything from the building to the hotel operations. The building has a "hybrid elevation structure," with the first basement floor to the eighth floor being made of reinforced concrete (RC, with part of the eighth floor being CLT), and the top three floors, from the 9th to 11th floors, being made of pure wood.
The entire building uses over 1,200 m3 of wood, more than 80% of which is from Hokkaido. The amount of wood used in the structure is the largest in Japan, and compared to a building constructed entirely of reinforced concrete, it has reduced CO2 emissions by approximately 1,380 tons, making it an effort to reduce embodied carbon.

木造部には過剰に荷重をかけられないため、一般的に見られる設備機器の屋上設置を避けることが求められました。このため、空調方式は機器重量と設置面積が小さい電気式の個別分散型方式を軸に計画。寒冷地仕様の空冷ヒートポンプパッケージエアコンを採用し、木造躯体とはエキスパンション・ジョイントで構造的に分離した屋外鉄骨階段の各階に設備機器を設置しました。
また、外調機、ボイラー、貯湯槽といった主要な機器はすべて地上1階と地下1階に納めました。スペースの少ない機械室ではおさまりの検討に苦労しましたが、こうした取り組みにより、札幌都心部を見渡せる、心地よいウッドデッキのテラスを屋上に実現することができました。

Because the building has a "hybrid structure" in which two different structures, wood and reinforced concrete, are combined vertically, we had a hard time considering construction methods for the facilities that would suit the different vibration characteristics. In particular, the drainage pipes on the guest room floors run vertically through floors of different structures, and there is a large difference in horizontal displacement during an earthquake between wooden and reinforced concrete floors. It was difficult to solidify construction guidelines (a summary of materials, procedures, safety measures, etc. for accurate construction) for the support method for the piping that would suit the characteristics of this building, but we were able to come up with a solution after patiently considering and discussing support methods with the contractors on site.

In order to create a space where wood can be felt even in the reinforced concrete guest rooms on the 3rd to 6th floors, "MI Deck" was used, which uses domestic wood as "formwork material" and "finishing material", and by eliminating the need for suspended ceilings, high ceiling height was ensured while reducing costs and construction time. Since the guest rooms are located at a height of 31m or less, they are not subject to interior restrictions and the "MI Deck" is not flameproofed. However, since there is no space to install equipment inside the ceiling in the part of the folded ceiling that uses "MI Deck", the piping of the fire sprinkler is exposed on the ceiling surface. Therefore, by using a side wall-mounted sprinkler head instead of the general ceiling-mounted type, the wood on the ceiling surface can be beautifully displayed.

As carbon neutrality in the construction industry becomes a growing social demand, it is expected that the demand for wooden construction as a building material will continue to grow in Japan, where two-thirds of the country's land area is covered by forests. However, using wood for high-rise buildings poses a number of challenges, such as making them fireproof and strong. This is because ministerial certification of related construction methods is required to ensure the technical performance required for fire-resistant buildings.
We also need to continue to solve the issues we have introduced here regarding the compatibility with facilities. In addition, wood construction and wood-renovation work, which is expected to increase in the future, will require harmony with the existing structure. In order to respond to these challenges and demands, we would like to utilize the knowledge we have gained from this project, which is a high-rise hybrid building made of wood and reinforced concrete.