Synopsis: This article describes the construction of an energy-efficient home suitable for Montana’s extreme climate using Rastra blocks, which are insulating forms made of concrete mixed with recycled polystyrene that can be stacked into walls, foamed in placed, and then filled with concrete.

Stick-frame construction is all but dead in Europe, and for good reason. Wood is too scarce and too expensive to use as a hidden structural element as it is in U.S. residential construction.

Instead, European builders use wood primarily for decorative details. Masonry construction is standard, as I learned in years of job-related travel that took me to Europe. When I moved to Montana a few years ago and built a house, the technologies I had seen in Europe made more sense than standard wood-frame construction.

Weather conditions in the mountains of southwestern Montana are brutal: scouring winds, 90°F summers and –40°F winters. The climate seemed ideal for one of the best European products I had seen, an insulated concrete block called Rastra. Developed in Austria, the block is a type of insulated concrete form that is dry-stacked, reinforced with steel, and then filled with concrete. Eighty-five percent of the material’s volume is recycled polystyrene, which is shredded into beads and mixed in forms with cement to make the block. Once completed, walls resist fire, earthquakes, wind, water, and insects. Houses built this way are unbelievably comfortable summer and winter, and pleasing to the eye to boot.

I am not a builder by trade. But my budget was tight, so I joined the construction crew that consisted of architect-builder Matthew Beardsley of the Baukunst Company in Bozeman, and one other person. We used block from a now-defunct company called Ener-Grid to build my house. It seems identical to the block manufactured by Rastra. Another…