The number of concrete homes is growing, and now there is software available to correctly size HVAC equipment in these homes. In 1993, the above-grade concrete wall market for single-family detached homes represented 3% of new-homes contruction. Thanks to industry research and promotion efforts, the above-grade concrete wall market through 2003 was at 16%. Insulated concrete walls include insulating concrete form (ICF) walls, removable-form concrete walls, precast concrete walls, autoclaved aerated concrete (AAC) walls, and concrete masonry (CMU) walls. Houses constructed with concrete wall systems, if built properly, are quiet, comfortable, disaster resistant, sustainable, insect resistant, and energy efficient. Concrete's inherent thermal mass, the high level of insulation in some applications, and the low air infiltration of concrete walls all serve to increase energy efficiency. A variety of studies have compared the energy performance of concrete homes to that of wood frame alternatives (see ICFs Under the Microscope, HE Nov/Dec '02,p.36 and ICFs in North Texas, HE Nov/Dec '02.p 39). One study sponsored by the Portland Cement Association (PCA) compared the energy use of identical contemporary houses wuth various exterior walls in 25 North American locations. Due to the thermal mass of ...