Cx Monitor: BECx and Energy Efficency
Modern building enclosures are designed and constructed using numerous complex systems and materials. Combined with demands for quality, durability, schedule, and energy performance, it’s not surprising that the building enclosure represents the majority of building failures and construction defect claims. Simply defined as a quality-based process implemented to evaluate and verify the owner’s project requirements (OPR), Building Enclosure/Envelope Commissioning (BECx) provides a reliable process for facilitating the necessary quality assurance to achieve project success.
Many early BECx programs focused almost exclusively on minimizing or eliminating water leakage through the building enclosure. While this continues to be a critical aspect of enclosure quality assurance, energy-related goals also play a considerable role in the comprehensive BECx process. Like all project performance goals, early documentation within the OPR is the first step.
The Enclosure OPR and Energy Performance
Quantitative performance goals related to effective thermal performance values, air leakage, etc. must be included within the OPR document. Many building codes, states, and other institutions have recently implemented requirements related to continuous insulation and quantitative air barrier performance. While these requirements can often form a baseline for performance, energy modeling can be utilized to further define quantitative goals. Through communication between the commissioning team and modelers, appropriate and cost effective performance metrics can be more accurately identified and included within the OPR. The mechanical engineers can utilize the information provided by the energy model to assist with HVAC design and equipment sizing.
After documentation of the OPR, it is the responsibility of the commissioning agent to verify the objectives outlined are being achieved throughout design and construction. The following summarizes tasks commonly performed within a BECx program to assist in this verification process:
- Design reviews
- Test plan development
- Coordination meetings
- Submittal and shop drawing reviews
- Mock-up construction and testing
- Construction observations
- Field testing
While it has long been recognized that insulation within building enclosures can improve overall energy performance, several recent studies have indicated that air leakage across the enclosure can also significantly impact energy performance. Experienced consultants and contractors may be able to reasonably predict total building air leakage based on the enclosure design and observations made during construction. However, a quantitative whole building air leakage test performed at the end of the project is the only way to determine the whole building air leakage rate.
In our experience, buildings that have utilized a BECx program reportedly have improved performance. The recently published ASHRAE 1478 Research Project substantiates these findings. The research project measured the enclosure air leakage of 16 existing buildings. Buildings that utilized a quality program administered by a building enclosure consultant were about half as leaky as projects that did not implement a quality program.
A more energy efficient building enclosure results when quantifiable performance metrics are identified, coordinated, and achieved, providing greater value to building owners. An experienced commissioning agent can help navigate and implement this complex process on new construction projects.
For additional information, please contact Rick Ziegler at RZiegler@ssr-inc.com.