The Equitable, or Commonwealth Building, was the first office block in the International style to be erected in the United States, Built in 1948, it created considerable controversy in Portland for being at that time a radical design, but was immediately praised by national critics for its design innovations and straight-forward use of materials: natural-colored aluminum sheathing, cast and anodized aluminum spandrels, and heat-absorbing double plate green tinted windows. Novel, too, was the use of a heat pump, which extracts heat from or discharges it to well water in the earth below to heat and cool the building. A modular approach to lighting and electrical service allowed great flexibility in locating interior partitions. Elegant, flexible, and economical, it foreshadowed what was to become the standard vocabulary for office buildings of the following two decades.