Residential ZNE Retrofit - Lessons Learned

Zero net energy (ZNE) homes are generally defined as homes that produce as much energy as they consume over the course of a year. Retrofitting a home to achieve ZNE or near-ZNE status, the primary focus of this report, requires intensive design work, including energy auditing, energy modeling, installation of energy efficiency measures (EEM), and coordination with the design team and installation contractors. ZNE goals can be easier to achieve in new construction, because the various materials are installed in sequence as the home gets built and the specialized trades, such as air sealing, can access the building at the correct time to achieve maximum results. Often a large gap emerges between what the design intends on paper and what is actually built in the field. This gap typically occurs when the contractors on the job sites are left alone to interpret drawings and specifications and then direct those under their supervision to build based on their interpretation. Adding ZNE dimensions to the communication breakdown that often occurs on construction projects increases the likelihood that some details will get overlooked, some items may be executed out of proper order, and some items will be built with incorrect or inferior materials. The goal of this project was to explore gaps and issues that emerged during a large ZNE retrofit project that would hinder the goal of smoothly reaching ZNE. The project also analyzed and documented solutions and lessons learned with the objective of providing a roadmap to help lower ZNE implementation barriers and provide industry stakeholders a more complete understanding on how to execute a ZNE project, from the original design to successful completion. This project focused on gaps, issues, and solutions that emerged during execution of the ZNE Retrofit Block project, which encompassed a retrofit of nine homes on one block to ZNE levels. Activities examined included energy audits; selection and installation of EEM measures; selection of, and coordination with, a general contractor (GC); and performance monitoring and inspections. The project analyzed and documented the gaps and solutions to provide guidance each step of the way, from the early design work through the completion of the construction phase to verifying ZNE performance after construction. The project found and analyzed multiple issues and gaps, and documented a number of mitigations and solutions. A principal finding was that by addressing gaps and issues, the ZNE Block Retrofit project achieved ZNE target goals. Other important findings follow: -Better communication, from design onward, is imperative to the success of the retrofit ZNE project. Details cannot be left up to interpretation. Clear communication of solid plans to those bringing the plans to fruition is instrumental in a successful ZNE Retrofit. -Ensuring a successfully built ZNE design requires a project manager (PM) and team with detailed knowledge of energy efficiency measures and energy efficiency (EE) construction experience, and especially construction scheduling knowledge overseeing the EEM implementation. However, many stakeholders with experience and skills in construction are not well versed in EEM or ZNE design and construction. Because ZNE is an emerging concept, and EEMs are still a relatively recent addition to the marketplace, an extensive training effort is needed to bring the industry up to speed on the latest techniques to achieve ZNE. Such training is now lacking, and many in the industry who are skilled in EEM/ZNE are self-taught, the cream of the crop, if you will.