The masonry industry should stop apologizing for masonry's relatively low R (heat resistance) values. Instead, the industry should tout the thermal storage capacity inherent in high-mass construction materials such as masonry.
Thermal Mass Concept
Many people don't understand the concept of thermal mass-that it moderates temperature change by absorbing heat and delaying its transfer. Energy transfer (heat flow) occurs because a temperature difference exists. Understanding this basic law of thermodynamics is a prerequisite to understanding how thermal mass works. Heat striking a building material thus will flow to the side of the material that is colder, whether on the building's interior or exterior. Heat flow in masonry is markedly different than in a low-mass material because masonry has a higher heat capacity (HC)- the capacity to store heat or remain cold. HC is defined as the amount of heat necessary to raise the temperature of a given mass 1º Fahrenheit. Specific heat is the quantity of heat energy (in Btu) needed to raise the temperature of 1 pound of material by 1º F. Thermal mass also can reduce total energy consumption by making a building less vulnerable to temperature fluctuations. The application with the most immediate significance is that thermal mass allows electric utility loads to be shifted to off-peak hours.
Peak Load Shifting
Because of masonry's capacity to manage energy usage through storage, it can be cooled and dehumidified with conventional energy-using appliances during off-peak hours, when electrical demand is lightest and inside/outside temperature differentials are less pronounced; the appliances then can be used minimally during the peak demand period, as the preconditioned masonry maintains comfortable temperature and humidity conditions. This is a win-win situation for utility companies, consumers, builders, and the masonry industry.