The apartment building at the end of Cosmonauts Street in the small Lithuanian town of Marijampolė is flashy for the neighborhood. Built in 1993, the narrow nine-story building is newer than a lot of the Soviet-era apartment blocks to be found across the city. After a renovation in 2018, the 54-unit building looks fresh, with alternating columns of peach- and cream-colored siding to distinguish it from towers of drab concrete.
Yet changes at the Cosmonauts Street building go beyond the cosmetic. Before the work-up, its energy use was typical for a building of its age, which is to say, not great. But after the retrofits — including new windows and insulation, solar and geothermal heating systems and all-weather glazed balconies — costs for heating the building fell from 140 kilowatt hours per square meter to 28, a decline of 80%.