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December 7, 2011 / mandyhyj

Moe -Interactive Surfaces

Moe explains that human skin is a thermally active surface. 47.5% of heat transfer is through radiant transfer. Skin “regulates deep and surface body temperature through hydronic exchanges with the integumentary and circulatory systems that use the skin as a thermal sink and source”. “Thermally active surfaces are based upon radiant heat exchange between a body’s skin and the mean radiant temperature (MRT) of a thermally active space.” The following diagram explained the heat transfer between the human body and different building parts through different means.

Moe pointed out in the reading that an important aspect of thermally active surfaces is that they are low-tech yet high performance and are thus equally applicable in the developed and developing worlds. I think this is one of the most important qualities of thermally active surfaces that distinguishes it from other sustainable design strategies. A design could only be sustainable when it’s affordable to most of people if not all. An economically demanding strategy is not sustainable by itself since the high capital input just discourages people from adopting it despite the great potential benefits the design could bring. Moe said in the reading that “unlike many approaches to integrated design such as BIM or digital fabrication, thermally active surface systems are not capital intensive economic proposals.” “Thermally active surface systems stand to make large changes in energy, material, and design practices with only small changes to contemporary practices.”

This reminds me of some vernacular thermally active surfaces that’s adopted by people in the rural part of northern China. Explained by Moe in his another writing, this design is called Chinese Kang, a thermally active bed. “In this system, the living space of the house was a few feet bove the level of the kitchen and fireplace in an adjacent room.” Hot air is channelled horizontally from the fire. There are slots built under the finished floor from the fireplace to and exterior chimney. The floor slab is made of concrete coated with clay. And on top of this are layers of oiled paper and floor mats. When heat warms up the concrete, the space above is heated up as well mainly due to radiant effect. the bed surface is then heated up as well and transfer heat to human body, mainly through conduction. Here, radiation is the main starting process of heat transfer, followed by more direct conduction. The following diagram explains this system.

This “Kang”, thermally active bed was very popular in northern China in the past when modern heating systems were not available. And the low cost of implementation made it prevalent in rural lower income parts as well. I think this example further demonstrates Moe’s point of the low economic cost and the equal availability to both developing and developed worlds, of thermally active surfaces systems. Though more new heating devices came out with modern inventions, this Chinese Kang is still in practice in northern part of China. This in turn demonstrated the sustainability and durability of the system.

 

 

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