What does this mean?
Massachusetts has a base energy code that all new buildings in the state must follow. It is based on the most current version of the International Energy Conservation Code (IECC) which establishes a baseline for energy efficiency by setting performance standards for the building envelope. Provided the mandatory requirements are met, the rest of the code can be met by either following the prescriptive or performance path.
Performance Path Compliance:
The performance path requires energy modeling to demonstrate that the building as a whole uses equal or less energy than a home built to the prescriptive path. Even though the performance path is slightly more involved, it allows flexibility to trade off many of the high-cost assemblies required in the prescriptive path resulting in substantial savings.
To comply with the Performance Path, you will need either a simulated energy performance analysis or an Energy Rating Index (ERI) analysis. The ERI path, specifically a certified RESNET HERS Rating, is the performance path most often used to achieve energy code compliance in base energy code communities.
We highly recommend following the Performance Path utilizing a HERS Rating. A HERS Rating is the most realistic compliance option that offers documented energy savings while giving you more flexibility and “trade offs”.
Prescriptive Path Compliance:
The prescriptive path requires that each component is built to a specified R-value or U-value found in the prescriptive table. While the prescriptive path is a traditional approach and can be achieved without the aid of any software, it does not have much flexibility and therefore does not allow trade-offs to lower assembly cost.
To comply with the Prescriptive Path, you will need:
- A REScheck certificate
- Performance Testing – blower door test, duct testing, and ventilation testing
- To meet insulation specifications
- To meet window performance specifications
**This path is not eligible for Mass Save incentives**