One important reason owners choose AAC for home construction is to save money on energy. Professionals refer to it as “structural insulation,” and claims that an 8-inch-thick AAC wall is more energy efficient than a 6-inch stud wall with R-19 insulation. The energy efficiency of a building product is determined by its R-value, thermal efficiency, and the effect of thermal mass. The R-value of a material is a measure of its resistance to conductive heat transfer, which is the energy that moves from molecule to molecule. The R-value of a typical 8-inch-thick AAC wall is R-10; a 10-inch wall is R-12.5, and a 12-inch wall is R-15.
But the R-value of AAC is only one of the ways it saves energy. As with a concrete wall, the mass of an AAC wall stores thermal energy when the ambient temperature is higher than the wall temperature. That energy is released when the ambient temperature drops below the wall temperature. This moderating effect can result in significant savings, especially in climates where temperatures vary widely during a 24-hour period. And, in a typical wood frame house, exterior air moving through the wall can account for up to 30% of the heating or cooling costs.Professionals says that they had the air-leakage rate of an AAC wall assembly tested, resulting in a leakage rate of 0.002 ft 3/min/ft2 at an air pressure of 1.57 lbs/ft2, which is significantly lower than for gypsum wallboard. Air infiltration around windows and doors can also be a significant factor in the thermal efficiency of a home.