夏季における樹木群の冷却効果 建物の微気象設計のための屋内外の放射エクセルギー分布の評価に関する研究

摘要

夏季の特に都市部の屋外広場、歩道では、ドライミストを噴霧し、その蒸発冷却効果により建物内外の温熱環境を改善し、暑さを和らげる試みが提案され、その効果が各所で検討されている。その一方、都市の屋内外空間の暑さには、空気温だけでなく、主に建築構造物や舗装床など、周囲を表面温度の高い地物に画まれたことに起因する放射も大きく寄与しており、街路樹で覆われることによる歩道の日射遮蔽効果について、MRT( Mean Radiant Temperature)、 SET~* (Standard Effective Temperature)やWBGT (Wet Bulb G1obe Temperature) により評価されている。幡谷らは、対策として樹木によって日射を遮蔽し、街路空間の地面の放射源自体の温度を下げて放射環境が改善される効果について、仙台市の二つの通りのSET~*を実測により求め比較している。%This paper describes the cooling effect of trees on outdoor and indoor environment in summer, making use of the concept of radiant exergy, which should be applied to the design of buildings and their surrounding open space. The measurement of air temperature, humidity, wind velocity, globe temperature and surface temperature for two days was carried out in order to estimate the radiant exergy of indoor space and outdoor space in the vicinity of buildings and where a lot of trees are planted. We compared the radiant exergy emitted from window surfaces towards the indoor space in north-facing rooms and that in south-facing rooms on the third and sixth floor. Hot indoor radiant environment especially in the perimeter zones, was found due to the warm exergy available from outside and the incident solar radiation reflected by brick pavement outdoors and the roof surface of residential buildings in the vicinity. We have confirmed, through this series of measurement and calculation, that the currents of "warm" and "cool" radiant exergy is useful in quantifying the radiant environmental conditions of indoors and outdoors.