Fall 2013 Research Update
CEE’s research department is undergoing a number of projects funded by the Minnesota Department of Commerce, Division of Energy Resources CARD (Conservation Applied Research and Development) Grant program. Read on for the latest findings and new resources from our field research in energy efficiency.
Heat Pump Water Heaters: Savings Potential in Minnesota
This white paper will characterize heat pump water heaters’ capacity to reduce space heating energy use in Minnesota homes. Primary investigator Ben Schoenbauer completed a market assessment of utility rebate programs around Minnesota, finding that heat pump water heaters have not penetrated the market. Homeowners and utilities hesitate due to a lack of reliable field data on energy performance and comfort.
The project team also wrapped up an assessment of modeling capabilities that identified a number of challenges typical of cold climates modeling, including basement installations. As a result, they are developing a "savings grid" to replace the model, a matrix that will guide professionals through a range of scenarios. Users will select their installation location, venting options, and smart controls to find potential energy savings. This grid will develop into an electric water heating calculator for homeowners.
Capturing Energy Savings from Large Building Envelope Leakage Reduction
The National Institute of Standards and Technology estimates that air leaks account for up to one-third of commercial and industrial buildings’ energy use. Field testing at seven sites will develop diagnostic tools and methods to quantify potential energy savings from air sealing. Work is complete for six sites and the seventh, Anoka-Ramsey Community College Cambridge, has agreed to complete air sealing. The project has created the largest US data set of the actual change in building tightness after performing air sealing. While Minnesota's building stock has different attributes and tends to be tighter than other parts of the country, the findings have applications in all climate zones. Project lead Dave Bohac published the paper Leakage Reductions for Large Building Air Sealing and HVAC System Pressure Effects and presented at the Air Infiltration and Ventilation Centre TightVent Workshop on Building and Ductwork Airtightness. A related article will be published in the International Ventilation Journal, and a final report will be available later this year.
Advanced Rooftop HVAC Unit Controls Pilot
RTUs serve over 40 percent of commercial floorspace, but upgrading to newer models is expensive for small businesses. This pilot is field testing two of the first advanced control strategies. However, results so far suggest that these particular packages are not a one-size-fits-all solution, and aren't a cost-effective retrofit in Minnesota's climate.
To help disseminate research findings, the Innovation Exchange completed a series of animations illustrating how RTUs work. A final report will be available in early 2014.
Condensing Boiler Optimization for Commercial Buildings
Project lead Russ Landry reviewed the commercial condensing boiler market and found that the majority of commercial boilers installed over the past few years are high efficiency condensing boilers. This is true whether the installation is part of a new building or the replacement of an old boiler. The dominance of condensing boilers indicates the potential to save significant amounts of energy by optimizing these boilers. Project staff also uncovered more complex part-load efficiency issues that are not typically represented in product literature nor widely recognized by industry practitioners. Preliminary findings on the part-load efficiency issues suggest that a number of installations could have their operating efficiency improved through simple, low cost control setting changes. In response, CEE researchers will increase the focus on investigating part-load efficiency issues - in addition to the critical impact of boiler water temperature on efficiency. Over the next few months, CEE staff will finish selection and detailed monitoring setup for twelve condensing boiler sites representative of education, government, and apartment buildings. Sites are being chosen to represent a variety of common boiler system characteristics. Monitoring will be complete by the end of summer 2014. Stay tuned for an upcoming animation illustrating many pieces of this research.
Reducing the Energy Cost of Effective Ventilation in Multi-Unit Buildings
Nearly eighteen percent of Minnesota’s occupied housing units are in multifamily buildings. This field research is assessing multifamily ventilation systems with the potential to impact both building energy performance and occupant health. The project completed initial ventilation assessments for three buildings in CEE’s “Direct Install Plus” Multifamily Pilot Program (supported by CenterPoint Energy) and included findings & recommendations in owner reports. The pilot and research go hand in hand: program staff establish relationships with building owners, increasing the value of seeing every building unit by incorporating a ventilation assessments.
The research team is screening for potential sites and will choose four buildings for its next round of field assessments. A total of 15 to 25 buildings will be included in the project, the second round in a sample size of 15 to 25 buildings. Project staff are currently developing diagnostic procedures to accurately measure air flow rates from rooftop exhaust fans and procedures for computing energy savings. This has included the utilization of a previously developed multi-zone airflow model used for air sealing measurement. By simplifying procedures, staff are creating a process that an energy auditor could use to perform ventilation assessments at scale. Early findings show that in some buildings, improvements to correct under-ventilation do not result in energy savings.
Saving Energy by Reducing Duct Leakage in Large Commercial & Institutional Buildings
Duct leakage can cause significant energy penalties even though the ducts are entirely within the building enclosure. This research will characterize the leakage of existing large commercial and institutional building duct systems and develop air sealing screening and diagnostic procedures. Intuitively, sealing ducts for customers with leakier ductwork will save the most energy; to better understand this target market (types of buildings, types of duct systems, areas of the state), project staff interviewed sheet metal contractors, test and balance contractors, and code officials for feedback on types of designs, specifications for duct tightness, and implementation. While the survey responses were inconsistent, they provided useful and unique qualitative information from specialized audiences. CEE researchers are identifying candidate sites for field work and developing instrumentation to measure duct leakage. A tracer gas system, based on a patent from LBNL, will measure the airflow rate through the main branch of the duct system. Researchers are also working with The Energy Conservatory to develop a power flow hood to measure the airflow rate of diffusers. The difference between the total air flow rate at the main branch and the sum of the diffuser flows will be used to determine duct leakage under normal operating conditions.
Select Window Retrofit Technologies
While replacing energy inefficient windows can save energy, their cost is a major barrier to residential and commercial building owners. This project completed a literature review and product comparison of window films and panels, which could provide a cost-effective alternative to window replacement. Staff are also performing energy modeling of whole buildings with window films and panels added to them to find the energy impact of the products on six different types of buildings Minnesota’s climate. The building types include commercial buildings of various sizes, multifamily buildings and residences. They found that adding an interior panel makes single pane windows as efficient as double pane windows and also improved double pane to the level of triple windows at a much lower cost than a full window replacement.
Only about 25 percent of windows in the state are currently this efficient. If building owners replaced or installed panels in the other 75 percent, Minnesota could meet its 1 percent energy savings goal just using window retrofits. Over the next several months, staff will continue to refine the payback model by gathering real cost data for Minnesota installations. To determine additional non-energy benefits, they’ll also conduct interviews with people who live or work in buildings that have installed the panels. Register for the upcoming webinar The Impact of Window Energy Efficiency and How to Make Smart Choices to learn more.
*These projects supported in part by a grant from the Minnesota Department of Commerce, Division of Energy Resources through the Conservation Applied Research and Development (CARD) program. And with co-funding by CEE in support of its nonprofit mission to advance research, knowledge dissemination, and program design in the field of energy efficiency.