Thermal and Energy Performance of Autoclaved Aerated Concrete (aac)
Aerated Autoclaved Concrete (AAC) is a lightweight concrete that has been developed in 1930s in Europe and it is one of the most popular type of insulated concrete used worldwide. AAC is known for its superior thermal insulation compared to a normal weight concrete. However their superior thermal performance is not reflected by today’s energy standards in North America. Normal-weight concrete masonry units (CMUs), on the other hand, provide significantly higher thermal mass effect. Current energy codes give thermal mass credits to normal concrete, while discounting superior thermal resistance of AAC. This presentation documents investigation of the potential for superior energy performance of CMUs made of Autoclaved Aerated Concrete (AAC) over normal-weight concrete CMUs. First, thermal performance of a series of AAC-4 - 500 class samples was measured to establish a correlation between thermal conductivity and density. Based on this analysis, an appropriate density AAC sample was selected that provides high R-value. Next, a three dimensional modeling was performed to obtain equivalent wall values for CMU and AAC configurations considering representative thermal conductivities, densities, specific heat—that were time and temperature dependent—and thermal bridging. Finally, whole building simulations were conducted to evaluate heating and cooling loads for different configurations, showing the energy benefits of AAC CMU in North-East U.S compared to conventional two-core masonry units of the same R-value.
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