The utilitarian concrete block has gained new respect in recent years. Now called "concrete masonry units," or "CMUs," blocks are used increasingly as substitutes for conventional wood-framed, above-grade exterior walls.

Concrete masonry construction may cost slightly more, but builders and homeowners like its durability, strength, and heat-retention qualities. Insulation can be foamed or inserted into the hollow cores or applied as a rigid board to the surface to increase resistance to heat flow.

Concrete block won't burn, rot, or be eaten by termites. And it produces a wall that is secure, sound-deadening, and effective at reducing thermal swings. "If you want permanence, security, resistance to fire, wind, and insects, you ought to consider concrete masonry," says a spokesperson for the National Concrete Masonry Association. In addition, "Concrete masonry has a life that extends into the hundreds of years. It is still one of the most environmentally friendly products on the marketplace."

The cost of concrete-block construction varies from one area to the next. A concrete-block house can run from 5% to 10% more than a wood-frame house where builders aren't familiar with the material. The blocks themselves cost from 60 to 90 cents each.