Prescriptive and performance compliance paths are used to demonstrate the energy and water efficiency of a new home or remodeling project.
In general, prescriptive paths require that the home's components are built to a certain standard (e.g., maximum building envelope leakage rates — depending on climate zone) to earn points for that practice. Complying with a prescribed set of practices qualifies the project for certification, and additional practices can contribute toward higher certification levels, providing a straightforward path for compliance.
Performance paths require the home as a whole performs to a certain standard, usually a percentage savings better than a baseline. Performance paths allow the building professional to choose the practices best suited to their customer and market, and to maximize the benefits of analyzing the house as a system.
The ICC 700-2020 National Green Building Standard® (NGBS) allows builders to choose the best compliance path depending on their client, the project's geographic location, market conditions and permitting requirements.
In new construction, projects must satisfy a set of mandatory requirements for both energy and water efficiency, and then the builder may choose either path to complete the certification requirements.
- Prescriptive path – Points are earned for practices including building envelope, air infiltration, heating system efficiencies, cooling system efficiencies, duct sealing, water heating system efficiencies, lighting, appliances and on-site renewable energy.
- Performance path – Energy savings levels above the 2018 International Code Council (ICC) International Energy Conservation Code (IECC) are determined via modeling analysis. Points are awarded based on the percentage savings over code.
- Prescriptive path – Points are earned for efficient fixtures, appliances, structural plumbing, irrigation practices, and the use of innovative practices including water capture and reuse.
- Performance path (new for 2020) – A Water Rating Index alternative compliance path assigns a score of 0-100 for the project as compared to a standard home (the lower the score, the more efficient the home). The anticipated water savings from the project's design strategies and products for indoor and outdoor water use, as well as water capture strategies to offset potable water use, are calculated to determine the score. The score is then translated to a NGBS certification level.
For remodeling projects, the 2020 NGBS now offers prescriptive paths for both energy and water in addition to performance paths; remodelers can mix and match the paths they choose for a project (e.g., one prescriptive/one performance, both performance or both prescriptive).
- Prescriptive path (new for 2020) – A suite of practices is offered to improve energy and water efficiency. The number of points earned for selected practices determines the certification level achieved.
- Performance path – The NGBS Verifier determines the pre-renovation baseline performance for energy and/or water. The project installs strategies resulting in a reduction in energy consumption from 15-45% and/or water consumption from 20-50% to meet the certification thresholds from Bronze to Emerald.
The NGBS provides building professionals with an above-code optional third-party accredited building standard for green practices in the areas of energy, water and resource conservation, indoor air quality, lot and site development, and building operation and owner education. The rating system is designed for single-family, multifamily and mixed-use buildings, either for new construction or remodeling; it also includes green practices for land development projects. More than 230,000 projects have been NGBS Green Certified to date.
Download a free pdf or purchase a print copy of the 2020 NGBS to learn more.