There are two components of it.
Once the retrofit or the new construction is complete, for example, there's testing you do in terms of how airtight the building would be, because airtightness and insulation reduce demand for energy. This would be part of the construction process, in addition to the skills the builder needs to make those changes.
After the fact, a number of metrics are then used to verify the energy performance of the building. Energy efficiency—the amount of energy, both electricity and natural gas—is measured vis-à-vis established standards. You can benchmark that the performances are actually what the level of performance is—