The United States is seeing a promising upward trend in ultra-low energy (ULE) buildings. While much of this progress has occurred with new construction, it is beginning to spread to existing buildings. Over the past decade, a small but growing number of ULE building retrofit projects have been documented in more than 20 states.
This isÂ great news, because a highly efficient building stock is one of the cornerstones of a prosperous clean energy economy. Todayâ€™s buildings consume roughly 40% of all energy used in the United States, and retrofits of existing buildings can produce sizable energy savings.