© Valentin Jeck
What Materials Keep Buildings Cool?
由专筑网小R，王雪纯编译
空调的使用不仅是高成本，同时还会影响环境。在2016年，空间制冷就排放了1045吨的二氧化碳，占全球能源消耗总量的10%，这个数字仍然会逐步增加，国际能源机构预计，到了2050年，空间制冷所占用的能源消耗，会达到全球总量的37%。
Air-conditioning isn’t just expensive; it’s also terrible for the environment. Accounting for 10% of global energy consumption today, space cooling in 2016 alone was responsible for 1045 metric tons of CO2 emissions. This number is only expected to increase, with the International Energy Agency estimating that cooling will reach 37% of the world’s total energy demand by 2050.
Image Courtesy of the International Energy Agency
Image Courtesy of the International Energy Agency
而真正使空调排放有害的是一种名为氟烷（HFC）的制冷剂，空调需要它才能进行制冷降温。虽然在排放的二氧化碳之中，氟烷只占总量的1%，但是其影响却是二氧化碳的数千倍。
Air-conditioning units are in particular harmful because they rely on a refrigerant called Hydrofluorocarbon (HFC). While HFC only accounts for 1% of all greenhouse gas emissions, it is also thousands of times more potent than carbon dioxide.
Image Courtesy of the Climate and Clean Air Coalition
因此，在建筑设计中，使用一些能够自然冷却的材料可以减少使用者对于空调的依赖，从而减少对于环境的负面影响。下文中，我们列出了一些材料与结构形式，它们能够有效地调节建筑温度，提升能源效率。
热质量与隔热
诸如石头、混凝土、生土等高密度材料都能够有效地起到隔热的作用。这些特性包含有较好的导热性质、缓慢的传热速度、较低的反射率、较高的热量存储能力。如果在建筑中大量使用这些材料，建筑的隔热特征就会增加，相关的案例有Kapsimalis Architects事务所设计的圣托里尼夏日洞穴住宅，而诸如A-cero的混凝土二号住宅等其他项目也同样是应用混凝土墙体来达到类似的效果。
Designing with materials that are naturally cooling can help mitigate these environmental effects by reducing the need for air conditioning. Below, we compile some material and structural solutions to passive cooling that may help designers regulate building temperatures energy-efficiently.
Thermal Mass and Insulation
Dense materials such as stone, concrete, and earth each have a number of properties that allow them to act as good insulation from heat. These alternately include good thermal conductivity (ability to rerelease passive cooling), thermal lag (slow heat transmission), low reflectivity (lower redistribution of heat), and high volumetric heat capacity (elevated ability to store heat). When such materials are used in bulk, their insular qualities become especially potent, exemplified by unique ‘cave homes’ such as Kapsimalis Architects’ Summer Cave House in Santorini. Other projects, like A-cero’s Concrete House II, rely on thick concrete walls to achieve similar effects.
Image © Vangelis Paterakis
传统住宅中很少应用到这些厚重的材料，它们一般依赖于高效的隔热系统。一般来说，隔热能力通过“R值”来进行评估，R值越高，那么材料的隔热能力就越强，诸如聚苯乙烯、聚氨酯泡沫和酚醛泡沫等材料的R值就较高，因此隔热效益也较好。
More traditional homes may not use such bulky materials but rely on effective thermal insulation instead. Typically, the thermal resistance of insulation is measured by what is called the ‘R-factor’ or ‘R-value.’ The higher this value, the more thermally resistant the material, and the more effective of an insulator it is. Materials such as polystyrene, polyurethane foam, and phenolic foam are examples of thermal insulators that have phenomenally high R-values.
Image © Luis H. Segovia
自然材料
在A-cero的混凝土二号住宅项目中，除了厚重的混凝土墙体，还应用了许多自然元素，其中包括绿色屋面和绿植墙体。绿色屋面不仅看起来美观，还具有遮阳的作用，隔绝一定的热量，降低屋面的温度。另外的著名案例则有由伦佐·皮亚诺设计的加州科学院、CPG的南洋艺术学院，以及Enric Ruiz-Geli设计的Bio别墅。
Natural Materials
Besides its thick concrete walls, A-cero’s Concrete House II and a multitude of similarly heat-conscious designs utilize natural elements such as green roofs or ivy walls. Green roofs are not only aesthetically pleasing, but they also provide shade, remove heat from the air, and reduce the temperature of the roofs. Some notable examples include Renzo Piano’s California Academy of Sciences, CPG’s Nanyang School of Art, and Enric Ruiz-Geli’s Villa Bio.
Image © Tim Griffith
根据当地的气候，建筑师还可以在建筑中结合水系统，通过水的蒸发和空气的流通让建筑降温。这种方法在早期就为罗马人所应用，他们常常在建筑中设计中央水池。
Incorporating water into a building can likewise cool a home through evaporation and air flow, depending on the climate. This methodology was recognized as early as the Romans, who often designed their homes around a central courtyard pool.
Image © Luis Gordoa
窗户的材料与位置
但是对于普通人来说，在家里设计水池或是绿色屋面有些不切实际，更简单的选择是使用被动式冷却技术，玻璃的太阳热增益系数（SHGC）越低，其传递的热量也越低，建筑就会更凉爽。这可以通过外部的百叶窗而得以实现，百叶能够有效地遮挡照射到窗户上的阳光，从而减少进入室内的光线与热量。而对于窗户的位置来说，建筑师可以尽量地满足交叉通风，促进室内的空气流通，从而达到降温的目的。此类案例有Louisiana猎枪住宅，这座建筑就将室内空间中不必要的墙体减少，尽量满足自然通风的需求。
Window Material and Placement
Green roofs and water features may seem excessive to the average homeowner or designer, but passive cooling can also be as easy as choosing the right glass for a building’s windows. The lower the solar heat gain coefficient (SHGC) of the glass, the less heat it transmits and the cooler the building. These benefits can be increased with external blinds, which prevent sunlight from hitting the windows at all and thus reduce the amount of heat or glare that reaches the interior. Even the positioning of these windows can have passive cooling effects through cross-ventilation, or the aligning of windows to facilitate air circulation. Notable examples of cross-ventilation include Louisiana shotgun houses, which minimize interior walls that may obstruct horizontal drafts.
Image Courtesy of the Efficient Windows Collaborative
屋面
最后，浅色的反射屋面也能够通过改变阳光的方向来减少室内空间对于热量的吸收。举例来说，有覆盖物的屋面、反射瓷砖、反射涂料都能够起到类似的效果。一般的标准屋面或是深色屋面在阳光直射下的温度能够达到150华氏度，而这种浅色的屋面在同等的照射条件下可以减少到50华氏度。
Roofing
Lastly, light-colored reflective roofs, another alternative to green roofs, can effectively cool interiors by redirecting sun rays and decreasing heat absorption. Examples include roofs with sheet coverings, reflective tiles or shingles, or reflective paint. While standard or dark roofs can reach 150 degrees Fahrenheit in intense heat, ‘cool roofs’ may only reach 50 under the same conditions.
Image © John Wilson
另外，较高的屋面和穹顶也能够让温度升高，而灰空间门廊和雨棚则可以为室内空间遮挡太阳。总的来说，材料和结构结合考虑能够减少使用者对于空调的依赖，同时减少有害气体的排放。
High roofs and cupolas may also allow existing heat to rise and escape areas in use. Similarly, covered porches and awnings can protect interiors from sunlight and glare. Altogether, material considerations and structural design go hand in hand to create effective alternatives to air-conditioning and mechanical cooling, decreasing HFC use and detrimental greenhouse gas emissions.
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