Moving back to the winter months and there are studies showing that thermal mass helps reduce the heating requirements of buildings too. I have previously
blogged about a report which shows that in spite of differing occupancy styles heavyweight buildings reduce heating requirements by up to 20% during the heating period. This is within buildings which have the same theoretical heat losses, same U-values, just different materials used in their construction. Some of this could be because the way the demand slowly builds on the heating system in a heavyweight house as it cools slowly. A lightweight building will cool more quickly, possibly putting higher demands on the heating system but in shorter bursts, making the system much less efficient. The speed at which heat travels through the walls (diffusivity) will also have some bearing on it too. Some natural fibre materials use water as a phase change material within their fibres to store and release heat prolonging the time taken for the heat to travel through the walls. Some of it will be to do with storing solar gains but, whatever the reason, a 20% reduction in your heating bill is not to be sniffed at.