Despite persistent low energy prices, building energy efficiency continues to improve, at least partly due to regulations, such as the European Buildings Directive, which will require “Nearly Zero-Energy” buildings starting in 2021.

The Passive House approach to building superinsulated, high-efficiency buildings is also making inroads, and makes building a net-zero building or nearly-zero building easier. According to the Passive House Database, nearly 3,500 buildings have been certified worldwide. That is a small number, certainly, but it is growing as builders become more…