The EDR has three components: 1. efficiency EDR, 2. PV/flexibility EDR, and 3. total EDR (also called final EDR). The efficiency EDR is based on the energy efficiency features of the building, including the envelope, HVAC, and hot water-heating features. The PV/flexibility EDR score captures the PV system, battery storage system, precooling strategy, and other demand responsive measures. The total EDR combines the efficiency EDR and PV/Flexibility EDR into a final score. The approved programs do not allow installing more PVs in exchange for less efficiency. However, if PVs are coupled with a battery storage system, a modest credit known as the self-utilization credit is available for tradeoff against the efficiency features. Approved compliance programs allow installing more energy efficiency in exchange for a smaller PV system.
Compliance requires meeting two different criteria:
•Proposed efficiency EDR must be equal or less than standard efficiency EDR, and
•Total EDR (efficiency, PV, battery storage) must be equal or less than total standard EDR.
The efficiency EDR is the building’s efficiency without any solar generation. The total EDR includes solar generation and any battery storage. This means the building must be energy efficient and it must generate enough energy to offset the electricity used to operate the building.
The standard design efficiency is based on prescriptive requirements. Two major changes to the standards are quality insulation installation (QII) and solar generation. Although not mandatory, performance compliance will be much more difficult to achieve without QII.
More information about the prescriptive solar electric generation Chapter 7 of this manual or the ACM Reference Manual.
Heat pumps will require verification of their capacity. Because the capacity affects the use of electric resistance back-up heating, a HERS Rater will verify the installed capacity meets or exceeds the capacities modeled for compliance. Software users can either enter the heat pump capacities (at both 47 and 17 degrees) or use an automatic sizing function. (Reference Appendix RA3.4.4.2.)
Whole house fans provide a significant compliance benefit in some climate zones. Software users will have three options, two of which require HERS Rater verification of airflow and watt draw: (1) specify a fan airflow, (2) select the default fan airflow required for prescriptive compliance with HERS verification, or (3) select the default fan airflow without HERS verification (the effectiveness of the whole house fan is derated by 7 percent). When verification is required, a HERS Rater will verify the watt draw and airflow rate. (Reference Appendix RA3.9.)