In the recent heat wave conditions of early 2014 where temperatures reached the mid-40s, our houses did not need air conditioning to maintain a constant temperature of around 25 degrees effectively making them ‘climate proof’ The use of thermal mass significantly reduces energy usage in residential buildings and provides the ability to maintain a comfortable internal temperature in a house with no mechanical cooling and minimal mechanical heating. This is important as the cost of electricity rose approximately 94% between December 2007 and March 2013. Thermal Mass is a measure of the heat storage (thermal) capacity of a material. High thermal mass materials take a long time to heat up and a long time to cool down ( Thermal Lag). When exposed to external (solar) heat, materials with high thermal mass (heavier and denser materials like concrete, stone, solid brick) can store more heat than their light weight low thermal mass (straw bale, timber, brick veneer) counterparts. This means that it is possible for high mass buildings to suppress or ‘dampen’ maximum indoor temperatures. Time delay and Damping (Decrement factor) Time delay or thermal lag plays a large part in thermal efficiency. Thermal capacity means that a material takes a long time to heat up and a long time to let this heat through and to release the heat; this delay is known as thermal lag. For instance, Concrete 100mm thick has a 4 hour lag and concrete 300mm thick…
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