Field Notes Summer 2020
This month we report on:
This post complements our Field Notes newsletter, which features quarterly updates on CEE's research projects. Sign up for Field Notes to get this information in your inbox.
Power Plant Host Communities
On May 21, CEE’s Audrey Partridge and Brady Steigauf hosted a webinar discussing the findings of the recent study report “Minnesota Power Plant Communities: An uncertain future.” Representatives from each of the six communities that were part of the report took part in a Q&A panel as part of the webinar.
Watch the webinar or download the slide deck.
This study was funded by the Just Transition Fund; the Coalition of Utility Cities; the Initiative Foundation, a regional foundation; the Southern Minnesota Initiative Foundation; the West Central Initiative Fund; Xcel Energy; and Center for Energy and Environment.
Field Study of Standalone Dehumidification Efficiency Opportunities
Background: Despite the prevalence of dehumidifiers in Minnesota homes, there is surprisingly little public data available about their use, performance, or energy efficiency in our climate. CEE led a project to understand the single-family market for dehumidifiers in Minnesota and monitor their energy performance. Researchers analyzed the relationship between the amount of moisture and efficient operation of standalone dehumidifier units, while maintaining desired indoor humidity levels.
Update: The project is in its final stages preparing for dissemination. Researchers shared the following overall findings:
Possibly the most notable finding was that portable dehumidifiers in Minnesota basements use 2–3 times the amount of energy than expected based on their rated specifications. This happens because basements are cool and people like to keep them relatively dry — it takes much more energy to remove water from the air in that context than it would in the hot and humid conditions in which the dehumidifiers are rated. Of that increased energy use, 70%–90% is due to those environmental conditions, while the remaining 10%–30% is due to other factors such as short cycling.
Another important finding is that new ENERGY STAR® units use a lot less energy than the current spread of existing units in Minnesota homes. While the existing units each cost about $115/year to operate on average, the new ENERGY STAR units cost about $62/year under the same conditions. Approximately one-third of those existing units have a clear path to increased energy efficiency through replacement with these new units — a low-hanging fruit that will see significant impact on energy use with a quick payback.
The project also found that the amount of energy used by a dehumidifier depended on how dry residents wanted the conditions to be — for every 5% decrease in relative humidity, residents spent 12% more on operating costs.
A final report is forthcoming, likely before the end of the summer.
Learn more on the project page.
This project is supported by a grant from the Minnesota Department of Commerce, Division of Energy Resources through the Conservation Applied Research and Development (CARD) program, which is funded by Minnesota ratepayers.
Low-Rise Multifamily Energy Code Study
Background: Interpretation and enforcement of energy codes often differs across jurisdictions, and because of those differences, complying with energy code is generally more difficult than it needs to be. This study sought to increase understanding of current practices and opportunities for improving energy efficiency in multifamily buildings — a crucial first step in standardizing the implementation of key code measures to benefit building owners, designers, contractors, and occupants.
In addition to air tightness research reported on previously, CEE recruited and studied 25 low-rise multifamily buildings in Minnesota as part of this project.
Update: After CEE finished data collection at the end of summer 2019 and sent it to Ecotope for energy analysis, the findings revealed that most buildings in Minnesota met code requirements for all the measures explored in the study. The biggest opportunities for improvement in Minnesota low-rise multifamily buildings that did not meet code requirements included additional wall insulation; increased window U-factor values (which indicate how well a window insulates); and efficient lighting measures for exterior spaces (e.g., parking lots).
The final report is nearly complete and will likely be published in later summer 2020.
Learn more on the project page.
This research is funded in part by a grant from the U.S. Department of Energy.
Aerosol Sealing of Existing Residences
Background: Existing houses are notoriously leaky with unintended airflow from outdoors that results in additional space heating and cooling equipment loads. Manual methods for sealing air leaks within a building, even when diligently applied, can fall short of the ultimate tightness goal due to unrecognized leakage pathways. Although voluntary standards for envelope tightness have existed for decades, they have only become codified recently, and they only apply to new construction, not existing residences. CEE undertook a project funded by the U.S. Department of Energy to identify the best methods for aerosol envelope sealing of unoccupied, existing residences to improve tightness by 75%. The findings of this project will be used to drive market transformation and develop a best practice guide.
Update: One house participating in the project has already been sealed. It was an older house — built in 1915 — with significant leakage, and aerosol sealing managed to bring that leakage below the current code requirement for new homes. The following is a snapshot of some of the results of that work:
- Before any sealing work, the house had a leakage of 11.7 ACH50 (a measurement used to report air leakage — air changes per hour at 50 Pascals pressure differential).
- The builder removed the attic insulation to apply a coat of spray foam and replaced a few windows before CEE’s team got involved, bringing the leakage down 51% to 5.7 ACH50.
- After the project team performed approximately two hours of aerosol sealing, there was a 73% reduction from the original leakage, leaving it at 1.4 ACH50.
- Some of the leakage returned after the temporary sealing was removed, and by the final measurement aerosol sealing was seen to have reduced leakage by about 2.93 ACH50, or 57%.
The space and water heating systems in the house will be replaced with direct vent equipment that can operate safely in a tight house. A heat recovery mechanical ventilation system will also be installed.
Recruitment for the remainder of the project was put on hold due to the COVID-19 pandemic and subsequent lockdown, but the project team is now starting to recruit again. While the technology can be applied to any existing housing, low-income eligible housing is a particularly good opportunity and much of the recruiting has focus on organizations that work with this housing.
Learn more on the project page.
This project is funded in part by the U.S. Department of Energy, Building America program.