文章翻译

Cool roofs: Many of the roofs across London are dark in colour and probably reach temperatures in excess of 50-60o C on hot sunny days. Consequently they will store and release a considerable amount of energy back into the atmosphere. High roof temperatures will accelerate the deterioration of roof materials and in buildings with poor roof insulation contribute to increased demand for cooling energy and a decrease in indoor thermal comfort on upper floors. In contrast cool roofs built from materials with high solar reflectance or albedo and high thermal emittance may reach temperatures considerably lower than their low reflectance counterparts. This is because they absorb and store less solar energy during the day and thus are not major emitters of heat into the urban atmosphere at night. Apart from their reduced contribution to the development of the nocturnal heat island, cool roofs have obvious benefits for the lifetime of roofs as excessive contraction and expansion is avoided through a damped daily temperature range and absorption of ultraviolet radiation is reduced. Also there will be gains in terms of indoor thermal comfort through the reduced transfer of heat through roofs to the upper floors of buildings and reduced demand for active cooling systems. To ensure the effectiveness of cool roofs as a climate management strategy their reflectivity must be maintained as this declines with roof age and roofs need to be kept clean, as dirt and pollution lower reflectivity.

冷屋顶：伦敦许多建筑的屋顶颜色很深，在温暖的天气里温度可能达到50-60摄氏度。因此这些屋顶会储存并释放相当大的能量到至大气中，并且较高的屋顶温度会加速屋顶材料的老化，建筑中老化的屋顶隔热材料会消耗更多的冷量并且降低楼上的室内热舒适性。相比之下，由较高太阳反射率或反照率和较高的热辐射材料建成的冷屋顶，可以达到一个相对于低反射率屋顶较低的温度。原因是它们在白天吸收并储存较少的太阳能，因此夜间不是大气的主要热辐射源。冷屋顶除了控制夜间的热岛效应外，它的寿命也更长，这是由于它对气温日较差的阻尼作用和对紫外线辐射吸收的减少，从而避免了过度的收缩和膨胀而造成的。同时冷屋顶减少了建筑物屋顶向上层房间传递的热量和空调系统的运行，因而会增加室内热舒适感。为了保证冷屋顶作为建筑气候控制策略的有效性，随着屋顶寿命的减少需要维持其反射特性，并且保持屋顶清洁，因为灰尘和污染物的反射率低。

Green Roofs: Like cool roofs, green roofs, which consist of a growing medium planted over a waterproof membrane, can have a marked impact on the climate of the upper floors of buildings and their immediate environs. On hot sunny days rooftop temperatures may be up to 20-40o C cooler than a conventional flat dark coloured roof. As well as the gains achieved in terms of climate through their cooling effect as a result of evapotranspiration, green roofs reduce rainwater runoff by absorbing and slowly releasing large amounts of water, act as insulators and reduce noise for upper floor occupants, increase urban biodiversity through providing habitat space for birds and small animals, increase urban aesthetics and contribute to quality of life. As the climate impacts of green roofs are likely to be greatest during prolonged periods of hot dry weather their efficacy as a microclimate management strategy will depend very much on the maintenance of a regular programme of watering and vegetation care. Once water becomes limited and vegetation health deteriorates their climate behaviour will approach that of a dry bare soil surface, which although not ideal will still maintain temperatures at a lower level than the more usual roofing mediums).

像冷屋顶一样，绿化屋顶由防水膜上培育的生长物质组成，可以影响上层房间及其周围气候。