Often retrofits of measures like wall insulation are cost prohibitive for existing buildings but inexpensive for new construction. The opportunity to design a building energy efficiently to begin with enables more and better efficiency measures to be incorporated. For these reasons, new construction is treated differently in energy efficiency analyses than existing buildings.
The more new technologies and practices that are adopted in new construction, the more costs will come down and the measures can become standard practice.
In addition to efficient design, important aspects of new construction with respect to energy efficiency are commissioning, post-occupancy performance feedback, and benchmarking.