Scientists from RMIT University, Federal University and University of Melbourne in Australia studied how modern “smart” materials can increase the energy efficiency of modular houses (prefabricated homes) – one of the fastest growing segments of housing construction. Such houses are assembled at the production site and delivered in ready-to-use modules, thus reducing the time and costs. But they have one weakness – relatively low thermal insulation. This leads to high costs of air conditioning and heating, especially in the conditions of diverse Australian climate. The team of Australian researchers decided to check if certain state-of-the-art technologies (phase-change materials, aerogels and electrochromic glass) could make such homes more comfortable and more energy-efficient.
To do that, the scientists created a virtual prototype of a standard single floor modular house and applied specialized DesignBuilder software to perform hundreds of computer simulations. They “ran” this model through the climates of three major Australian cities: Melbourne with moderate climate, Pert with hot dry summers and Brisben with humid sub-tropical climate. In the model they successively replaced standard elements of the house shell (the walls, the roof, the windows) with “smart” analogues and observed the energy consumption dynamics.
The phase-change material was the first one to test – the substance, which (just like ice) absorbs big amounts of heat during melting and gives it away during solidifying. The scientists added a thin layer of such material inside the walls of the house. It worked differently in different cities. In Melbourne, this material was the most instrumental to decrease the load on air conditioning in summer, but in Pert and in Brisben – on heating in winter. The position of the material was the key factor: it demonstrated the best performance when the layer was closer to the inner side of the wall. A simple increase of the layer’s thickness did not provide for a proportionate performance improvement, but the correct smelting temperature selected for a specific climate was more important.
Aerogel was the next test-taker – an extremely light and porous material, one of the best thermal insulators in the world. Its thin layer (just 10 mm), added into the walls, proved to be an excellent winter heat retainer significantly decreasing the need for heating in all three cities. However, it almost did not affect the cooling of house in the summer. An important practical conclusion: aerogel just 1 cm thick demonstrated the same performance as 13 cm of standard mineral wool, which allowed to lighten the structure of module blocks significantly.
Electrochromic windows were the third element. These are “smart” glasses capable of becoming obscure upon command (automatically or manually), thus regulating the amount of solar heat penetrating into the house. The results of testing them were ambiguous. In Melbourne and in Pert, such windows provided for noticeable savings on heating decreasing the annual energy consumption by 8.9% and 3.8% respectively. But in hot and sunny Brisben, to everyone’s surprise, they were not instrumental in reducing the energy costs and even made them grow a little bit. This proved that the technology performance is strongly dependent on local climate and on control logic.
But the main success occurred when the scientists combined all three technologies in one model of the house. This was how they found the optimal combination: the walls with inner layer of phase-change material, the roof with aerogel insulation and electrochromic windows. This “smart cocktail” demonstrated impressive results decreasing the overall annual energy consumption by 15.6% in Melbourne, by 11.2% in Pert and by 6.1% in Brisben. The researchers also discovered that the house exposure in the cardinal directions impacted the performance of the materials. For example, the walls overlooking the north and the west, receive more solar heat, hence, the “smart” materials on these facades performed better.
Overall, the study of Australian scientists constitutes an important step towards creating affordable, quickly built and energy efficient housing. Of course, these technologies have their own deficiencies, and the key one is high starting price. However, reducing the weight of structures, savings on operation and the growing demand for “green” solutions with time can make such smart modular houses beneficial for everyone.
