Field Notes Research Update: Winter 2017
This blog post is taken from our Field Notes newsletter which features updates on CEE's research projects. Sign up for Field Notes to get this information in your inbox!
Packaged rooftop units (RTUs) serve the heating, ventilation, and air conditioning needs of a large proportion of commercial building space in the U.S. This project characterized the Minnesota market for RTUs and monitored energy use to better understand indicators of high and low performance issues. The project team completed analyzing data from 52 RTUs at 9 sites and developed consumption profiles for each RTU and each site. The load profiles show large variability across RTUs in terms of sizing, application, and site use. Given the relatively small sample size, these load profiles may not be representative of Minnesota’s entire RTU population but they may provide insights into possibilities for future research or analysis.
The team also conducted a sizing evaluation of RTUs at each site to determine their ability to meet the required load for both heating and cooling. This led to an interesting revelation: RTUs are typically sized to meet the cooling needs of a site and this often leads to oversizing when it comes to heating, creating serious comfort issues for occupants. When a unit is oversized for heating, the space it serves can experience dramatic swings between hot and cold air; more efficient sizing could solve these types of problems.
On March 22 project lead Seventhwave is holding a webinar (register here) to discuss results and will release the final report in the coming months. Read the interim report here.
Building envelopes are notoriously leaky with unintended flows between conditioned and unconditioned spaces that result in additional space heating and cooling. Current envelope air sealing methods can produce variable results and require expensive remedial sealing at later stages in construction. This project will evaluate the integration of a new aerosol envelope sealing technology into the home building process, working with builders to characterize the cost, performance, and seamless integration into construction.
The project team will work with two Minnesota and two California builders to conduct aerosol sealing of at least 26 houses. At a Minnesota kickoff meeting in December, the team met with builders to get initial feedback on the use of aerosol sealing in single-family new construction and recruit project participants. All of the builders expressed interest in the project and offered valuable insight on current sealing methods that could be eliminated such as interior poly, rim joist spray foam, and duct sealing. In the next couple months the team will work with their first Minnesota builder to complete on-site assessments of their houses currently under construction and develop a specific plan for eliminating current sealing and cutting costs. The team will then complete a demonstration of the sealing process on one of the houses.
Builder recruitment is currently under way. Check out the Builder Information and Aerosol Sealing FAQs handouts for more information.
Energy use intensity for indoor pool areas is three times higher than most other areas within a building. Indoor pool facilities are prime candidates for energy savings through improved recommissioning and operator training, and this project sets the stage to realize this potential. The project team completed initial monitoring at five sites and identified opportunities for energy savings from operational changes that they then worked with facilities to put in place. The team then completed post-change monitoring and is currently finalizing analysis of the actual savings achieved at these sites. Two of the sites show significant savings from changes to dehumidification controls, and the team has also seen savings from the use of a physical pool cover. However, liquid pool cover — a promising chemical retrofit option that spreads out on the top of the water and decreases the pool evaporation rate — did not lead to the expected savings at the one site where it was implemented, which was a surprise to the team. Overall, the biggest savings opportunities are not necessarily standard measures or specific improvements; most often the greatest savings can be achieved by identifying control issues and implementing simple, cost-effective changes.
The team has begun work on pool operator guides for technicians (such as contractors or on-site engineers) and engineers that include 17 relatively simple control checks to ensure that the system is operating efficiently. The guide will also provide clear directions on how to address any issues identified through the checks. Once complete, the next step will be to test the guide in the field and get feedback from pool operators and engineers. A similar guide is also being developed for recommissioning engineers and both guides, as well as the final report, will be available later this year.
This project was also included in Cold-Climate Research Roundup webinar.
Energy recovery ventilation (ERV) systems have the ability to reduce the heating and cooling energy associated with outside air conditioning by over 65%. This field research investigated nine Minnesota ERV units to see how they perform in the real world and identify common issues affecting performance. The project team completed field monitoring and consolidated data for the final analysis. Considering all nine systems as a portfolio of ERVs presented a convenient framework for discussing problems. The team identified three groups of ERVs:
High-performing units were meeting expectations and working according to design. These systems typically had robust documentation from design through current operation and were subject to rigorous commissioning procedures.
Basic-functioning units were saving energy but were also plagued by minor issues impacting performance, control, and operation. The consequences of these minor problems were indirect and the units still performed well over. However, the issues caused confusion and frustration among staff and promoted faulty assumptions and skepticism about ERVs.
Low-functioning units were effectively disabled due to control changes and negligent installations. These units did not deliver any energy recovery and longstanding problems went undetected as there was no strong indication of their dysfunction.
Identifying and addressing the issues of the low-functioning units is most important as the minor issues don’t always need to be addressed given that the opportunity for cost-effective modifications is minimal. Increased training and improved communication are key to successful energy recovery. To help with this the project team is developing two items that they plan to disseminate in 2017: the first is a basic guide to help the individuals responsible for ERV operation identify and assess potential issues; and the second is a longer paper that will condense project findings to explain how ERVs work and how various roles can work together to ensure efficient operation. A final report will also be available later this year.
Even when ducts are entirely within a building’s enclosure, air leakage from ducts wastes energy by increasing fan power and discarding conditioned air. This research characterized leakage in large commercial and institutional building duct systems and validated the efficacy of retrofit duct sealing to improve air sealing screening and diagnostic procedures. After completing the field work portion of the project, the team conducted a pilot to determine if it was possible to identify cost-effective retrofit duct sealing opportunities. The team identified four successful criteria for choosing cost-effective projects: system type, operating pressure, design flow, and apparent tightness. Using these criteria as the basis of system selection, average payback was reduced from 31 years to 7 years. The pilot results suggest that about 10% to 15% of Minnesota commercial and institutional buildings have appropriate operational characteristics and leakage rates that are high enough to justify retrofit duct sealing work with a moderate to good payback of less than 7 years. A final report with pilot results will be available later this year.
Some the above projects are supported in part by the Minnesota Department of Commerce, Division of Energy Resources, through its Conservation Applied Research and Development (CARD) program, with co-funding by CEE in support of its nonprofit mission to advance research, program design, and knowledge dissemination in the field of energy efficiency.