PHASE CHANGE MATERIALS

Commonly it is said that natural ventilation is the purest form of mechanism that should be used in buildings. But unfortunately natural ventilation is not sufficient to control the heating and cooling caused by the materials used in the construction of the buildings. That is why we use mechanical ventilation. We have been using mechanical ventilation in our buildings for quite some time. We are using HVAC system without understanding the effects caused by it on the environment. Mechanical heating and cooling should never be used as substitute for good design.  Hence the root cause is the use of materials in building construction industry. 

Phase change materials (PCM) are the answer to a certain extent to the problem mentioned earlier. PCM are products that store and release thermal energy. Phase change materials (PCMs) can store much larger amounts of thermal energy per unit mass than conventional building materials and can be used to add thermal stability to lightweight construction without adding physical mass. In lay man's language in the process of storing and releasing heat, the PCM retain a near constant temperature without the use of any external powered input. They maintain the near constant temperature dozen times more effectively than other thermal mass medium such as masonry. 

Three phases of water i.e. solid, liquid and gas are examples of different phases of material like water. Below is one such example of paraffin wax.

Another example is BioPCM. It is made out of waste product derived from the manufacturing process of soy, palm and coconut oil. The waste is then blended with  a nano scale thickening agent made of spherical bits of silica. The final resultant is a gel contained multilayer pockets of in flexible plastic film. 

PCM equips architects to reduce or to the extent of elimination of electrically used air conditioners. Following link is a classic case study of the use of PCM in Australian homes. 

http://www.architectureanddesign.com.au/news/solar-sellew-by-positive-footprints-uses-reverse-b