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Learn How to Avoid Energy Loss in Your Buildings

由专筑网小R，吴静雅编译

热舒适性在许多情况下会变得异常显著。在某个环境中，热条件充足时，人们的身体和环境保持恒定状态，那么人们就能够正常地进行活动，但是如果环境太冷或者太热，人们就能够立刻感受到情绪与身体的改变，当热平衡不稳定时，身体的热量与环境热量存在差异，那么个体就会出现不舒适的状态。

“温度与性能的关系的24项研究分析表明，相较于21℃与23℃，在30℃与15℃会让人体机能下降10%，这说明热舒适性对于办公室人员产生影响。近期的研究表明，在一个可控的环境中，在较冷的温度下，人体机能会下降4%，而在较热的温度中，人体机能则下降6%。[1]”

Thermal comfort becomes very evident when it is not attended to. When thermal conditions are adequate in one location, our body is in balance with the environment allowing us to perform activities normally. On the other hand, when a space is too hot or too cold, we soon see changes in our mood and body. Dissatisfaction with the thermal environment occurs when the heat balance is unstable, that is when there are differences between the heat produced by the body and the heat that the body loses to the environment.  
"An analysis of 24 studies on the relationship between temperature and performance indicated a 10% reduction in performance at both 30°C and 15°C, compared with a baseline between 21°C and 23°C – demonstrating the impact thermal comfort can have on office occupants. A more recent study, in a controlled setting, indicated a reduction in performance of 4% at cooler temperatures, and a reduction of 6% at warmer ones. [1]"

Image Courtesy of Saint-Gobain

让使用者不受天气的影响是建筑的重要功能之一，其中分为积极与被动两种方式，前者则是使用暖气与空调设备，后者是使用太阳能、自然通风，亦或是相应的建筑材料。冷却与加热技术能够有效地改善室内环境，但是这也会造成与外部环境相悖的建筑空间，这使得使用者需要在冷却与加热设备中花费高昂的成本。有着玻璃幕墙的办公大楼会在内部空间应用复杂的空调系统，来保持室内的恒温。

建筑的立面是重要组成部分，它能够起到隔离内外空间的作用，但是在设计时也应当充分考虑当地气候状况。在温暖地区，建筑尽量保持通风，那么建筑外部就可以保留大开口，而在寒冷地区，则应该让阳光尽量进入室内，保持室内的温度。热量一般从热区域流向冷区域，因此内外表面如果出现温度差异，就会出现热传递现象。

Protecting ourselves from the weather is one of the primary functions of architecture. This can be done in an active way (using heating or air conditioning equipment, for example), or passively, using solar radiation, ventilation, and materials in favor of the architecture. Although the advent of cooling and heating technologies has improved indoor conditions, they have also contributed to the creation of buildings that are poorly adapted to the environments in which they were installed, making them costly to cool, heat and enable comfort in their interiors. Office buildings with glazed facades, which are not specified with respect to local climate, relegate complex air conditioning systems to the task of maintaining a constant internal temperature.
The envelope of the building is an important part as it acts as a filter between the exterior and interior climate, and should take local climatic conditions into account when designing. In warm places, it is generally sought to ventilate the building as much as possible, with generous openings and shaded spaces. In a cold region, on the contrary, the envelope tends to allow the sun to enter the space, maintaining the heat in the building. The direction of heat flow always goes from the hottest to the coldest surface and the transmission occurs when there is a difference between the temperature of the external and internal surface.

Image © ArchDaily

Image © ArchDaily

一些研究探讨了建筑中热量损失的几个重要形式，一般来讲，墙体的热损耗率为35%，而门窗则为25%，屋面为25%，楼板为15%。这些热损耗来源于对流、热传递、辐射等等。这些现象的发生不可避免，但是建筑师有责任管理这些现象的速度，比如可以使用恰当的建筑材料与相应的技术，设计建造维持热舒适度的建筑立面。

Several pieces of research address the main forms of energy loss in a building. In general, the numbers are close to 35% for the walls, 25% for windows and doors, 25% for the roof and 15% for the floor. These heat losses occur by convection, conduction, and radiation. They will inevitably occur, but it is the architect's duty to manage how quickly heat is lost - this can be controlled through the use of appropriate building materials and techniques to establish and maintain a watertight building enclosure incorporating high levels of insulation.

Image © ArchDaily

首先要从概念上了解保温隔热与热惯性。保温隔热能够在冬天减少热损耗，在夏天减少热增益。诸如矿物棉、陶瓷纤维、塑料泡沫、聚氨酯等隔热材料都包含有许多空隙，空气或是其他其他填充于这些空气之中，就能够起到保温或是隔热的作用，它们能够有效地减少热损耗与热增益。热传递率用“U”来表示，这个数值能够表示穿过建筑立面的隔热程度，如果U值很低，那么保温隔热效果就比较好，如果U值很高，那么热量的损耗就比较大。另外一个概念则是热惯性，这表达了材料对于热量的保持程度，以及这些热量通过材料一点一点地与环境相融合的程度。热惯性高的材料对于温度差异大的环境中能够让人体的感受延迟一些，热惯性与早晚温差大的地区息息相关。在早晚温差小的地区，则可以采用热惯性较低的材质，来防止高温进入室内。

At this point, it is important to address the concepts of thermal insulation and thermal inertia. Thermal insulation reduces heat loss during cold seasons and heat gain during hot seasons. Insulation materials like mineral wool, ceramic fibers, Styrofoam and polyurethane generally consist of many voids. Air or other gases captured in these voids act as an insulator. They will help reduce heat losses and gains. We have already discussed how to calculate the thermal transmittance, also called the U-value, in this article. This value allows us to know the level of thermal insulation in relation to the percentage of energy that crosses the envelope; if the resulting number is low, we will have a well-insulated surface. A high number will alert us to a thermally deficient surface. Another important concept is thermal inertia, which is the characteristic of a material to retain the heat and return it to the environment little by little. Materials with high inertia will have a delayed reaction on changes in atmospheric temperature. The thermal inertia is relevant in regions with climates with large thermal amplitudes between day and night. In coastal regions and sites where there is little temperature difference in days, the adoption of materials with low thermal inertia is adequate to prevent high temperatures from entering the spaces.


墙体

Image © ArchDaily

为了减少内外空间的热量传递，因此需要使用一些诸如矿物棉等隔热材料，石膏同样能够改善热舒适性，而智能薄膜则能够增强密封性与湿度管理，涂料能起到有效的隔热作用，也可以减少恶劣天气的影响。

Walls
To reduce heat exchanges between the interior and exterior, it is important to invest in insulation materials, such as mineral wool, and their integration into façade systems. Plaster also acts to improve thermal comfort. Intelligent membranes assist in tightness and moisture management, while coatings can contribute by insulating and protecting against bad weather.


屋面

Image © ArchDaily

可以在屋面中应用一定的隔热材料，从而提升内部空间的舒适性能。在使用热惯性高的材质的地区，还可以将隔热材料与大型面板结合使用。而在使用低热惯性材质的地区，则可以使用轻质材料，同时结合隔热材料。使用白色瓷砖或是浅色瓷砖的成本较低，但是成果较好，因为这些材料能够反射阳光。

Roofs
It is always recommended to combine some type of thermal insulation to the roof for greater comfort inside the structure. In regions where it is advisable to work with high thermal inertia, it is recommended to build a massive slab with the final application of an insulator. In regions where it is possible to work with low thermal inertia, light linings can be used, but always with the application of thermal insulation. A technique that is widely used, and has proven positive results and low cost, is to paint the tiles white or use tiles of light colors, as they reflect the sun rays.


地面

Image © ArchDaily

地板的隔热作用常常受到忽视，但是它对于建筑楼层之间的热传递也同样重要。另外，墙面或是地面的覆层选择也会影响到使用者对于内部温度的感知。


门窗

窗户玻璃与建筑立面会让阳光进入建筑内部，但是也能够保留建筑内部的供暖体系所产生的热量，亦或是根据需求将热量排除。总的来说，阳光的控制可以概括为以下几个方面[2]：

• 吸收或阻挡自然光；
• 吸收或阻挡热辐射；
• 内部的热损耗；
• 内外空间的视觉连接。

在透明封闭空间的研究中，必须要考虑长短波。短波为可见光与红外线，长波为被加热体所发出的红外线，其中的关键在于，在减少窗户热损耗（U值）和增加或减少阳光热增益之间找到平衡。同时，表达太阳能因素的G值也同样重要，这是通过玻璃直接或间接传递给环境的热辐射比例。1.0的G值代表着所有阳光辐射的总体传递，而0.0的G值则表示没有阳光传递的窗户。在寒冷气候中，高G值能够带来更多的热增益，同时减少供暖的需求。而在炎热地区，低G值能够控制不必要的热增益，则减少冷却需求。下图便很好地表达了某些类型玻璃的热传递方式。

Floors
Although often overlooked, the insulation of the floor is important to reduce heat exchange between the ground and the building. In addition, it is important to mention that the choice of wall or floor covering will influence the perception of temperature by the occupants.

Windows and Doors
Glass in the windows and facades can allow solar radiation to enter the environment, but can also conserve the heat produced by the occupants, the heating systems inside the building, or allow the heat to be evacuated, depending on the type of building. In short, the control of solar radiation can be summarized in [2]:

•Admit or block natural light;
•Admit or block solar heat;
•Allow or block heat losses from the interior;
•Allow visual contact between interior and exterior.

For the study of the behavior of transparent closures, it is important to consider short waves and long waves. Short waves are visible and infrared. Long waves are infrared radiation emitted by heated bodies. The key is to find a good balance between the window's ability to reduce heat loss (u-value) versus its ability to increase or reduce solar heat gain. At this moment, the G-value (Solar Factor) is important, which is nothing more than the percentage of solar radiation that hits the glass and is transmitted directly and indirectly to the environment. A G-value of 1.0 represents the total transmittance of all solar radiation, while 0.0 represents a window without solar energy transmission. That is, in cold climates, a higher "g-value" helps to provide more useful solar gains and limit heating needs. In hot climate countries, a lower "g-value" helps control unnecessary solar gain to limit heating needs. In the figure below we show the operation of some types of glass.

Image © ArchDaily

成功的设计策略能够影响到使用者的感受，每种材料在设计过程中都发挥着自身的作用。最终的成果应该优化功能，同时给使用者带来舒适的感受，因此建筑师也需要了解环境背后的原理，同时也要了解特定材料对于建筑功能与性能的整体影响。

Successful decisions influence the living conditions of the occupants, and each material can play a role within a general design strategy. The final specification should not only optimize power consumption, but also provide comfort to the user, that is why it is so important that architects know a little about the theory behind the phenomena and how the characteristics of the specified materials will influence the performance of the building in all its complexity.


参考文献

[1] Wargorcki P (ed), Seppänen O (ed), Andersson J, Boerstra A, Clements-Croome D, Fitzner K, Hanssen SO (2006) REHVA指导: 办公空间的室内气候与生产力. Lan L. Wargocki P. Wyon DP. Lian Z. (2011) 办公空间的热舒适性对于空气质量感知、SBS症状、生理反应、人类行为的影响.
[2] Lamberts, Dutra, Pereira (2014). Eficiência Energética na Arquitetura.

References
[1] Wargorcki P (ed), Seppänen O (ed), Andersson J, Boerstra A, Clements-Croome D, Fitzner K, Hanssen SO (2006) REHVA Guidebook: Indoor Climate and Productivity In Offices. Lan L. Wargocki P. Wyon DP. Lian Z. (2011) Effects of thermal discomfort in an office on perceived air quality, SBS symptoms, physiological responses, and human performance.
[2] Lamberts, Dutra, Pereira (2014). Eficiência Energética na Arquitetura.