Winter 2014 Research Update
Welcome to our winter research update. The cold Minnesota weather is not keeping the research staff from getting out in the field. We have a lot going on in our department. This update covers a portion of our ongoing research, highlighting the recent findings from our CARD funded projects. Read on to learn more about those projects and be sure to visit the CEE Innovation Exchange website, where you will find project pages covering all our current research.
-Dave Bohac, Director of Research
Heating and air conditioning can account for over 25 percent of energy use in commercial, retail or industrial buildings. Rooftop units, or RTUs, serve 40 percent of the floor space within those buildings. Over the course of a year, CEE staff tested three different optimization packages (Premium Ventilation, Digi-RTU Optimizer, and Catalyst Optimizer) on 66 RTUs across six different sites. This project is one of the largest studies on RTUs in the country and is the only study completed in a Minnesota climate.
Official field testing ended in August 2013. Research staff have since completed all calculations, finalized the savings analysis and created cost-effectiveness models to understand and show the results of the field testing. The initial findings found that all the technologies achieved significant electric savings, while gas savings were negative or insignificant. More investigation is needed to determine the reason for the increase in gas consumption. Both CEE staff and the manufacturers were especially interested to see how the technologies worked in the cold climate. All three technologies had issues with the extreme cold, and as a result of the findings, some manufacturers changed their equipment to operate more reliability and efficiently in our climate.
More information on the results will be available in the full report, available in early 2015. In addition, Project Lead Mark Hancock presented study results at a CEE Innovation Exchange webinar last month.
The 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. This project is setting the stage for realizing this potential energy savings. Project staff have selected 30 different pool facilities to survey and are on track to complete all 30 by the end of the year. All of the sites are located in the metro area and can be divided in to two different groups based on pool size. The first group is made up of larger pools over 2,000 square feet, and includes mostly fitness centers and schools. The second group is small pools, which are mostly found in hotels, motels and multifamily buildings. Each survey assesses three main aspects of the facility – the basic size of the pool and pool area, the physical characteristics of the pool and space conditioning equipment, and the operations practices. Survey results have shown significant variations in everything from the type of equipment, to the operating schedules and practices, to the temperature and humidity controls.
Staff are now beginning to assess the survey information for any trends, and from there will select six sites representative of the variety of typical Minnesota commercial indoor pool facilities to perform recommissioning and quantify savings achieved. Based on early assessments, there will likely be a lot of opportunity for optimization by simply adjusting the temperature and humidity settings. Over the next year project staff will begin to develop guides for energy efficient operation and recommissioning of indoor swimming pool facilities.
This report is characterizing heat pump water heaters’ capacity to reduce residential water heating energy use in Minnesota homes. Project lead Ben Schoenbauer worked with design and IT staff to develop calculator apps for homeowners and utilities. The homeowner app is currently available on the CEE Innovation Exchange website and is geared towards homeowners without natural gas service. It tells users their expected energy savings after switching to a heat pump water heater and quantifies how it would affect their energy consumption and peak load. The project team is finalizing an interactive calculator for utilities, specifically geared for utilities in areas where there is a prevalence of electric water heaters. The app uses Minnesota averages to demonstrate the potential impacts on peak usage if a certain number of customers switch to heat pump water heaters. The results are a good estimation of the ranges of expected savings, but more research is needed if utilities need fine details. Field research could help identify additional opportunities and could help classify the impacts in real world situations. Heat pump water heaters provide peak savings when operating under normal conditions, but provide further peak reduction if used by demand control programs through strategic time of use. A final white paper providing a range of expected savings and highlighting peak reduction will be published in early 2015.
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 indoor air quality. The project is wrapping up and will finish in early 2015. The final stage of the project retrofitted two multifamily buildings using two different techniques. The first retrofit used an aerosol sealant to seal exhaust shafts for both bath and kitchen vents throughout the building. The leaks were too large to be completely addressed using this method, but lack of access will make more traditional sealing methods difficult to implement. The second building followed CEE’s retrofit guidelines, with the help and guidance of project staff. There was success with sealing the kitchen exhaust system to code levels that will save energy, but the bath exhaust systems had issues achieving uniform flow in lower units. Project staff are following up to identify and seal the leaks.
The project team has been working to finalize a multifamily ventilation manual, which will include screening and diagnostic protocols for contractors. The team will then offer training sessions for Minnesota multifamily energy auditors to receive feedback and refine the guidelines. This is the first complete manual to be produced on multifamily ventilation guidelines.
Energy recovery ventilation systems, or ERVs, have the ability to reduce the heating and cooling energy associated with outside air conditioning by over 65 percent, and are becoming much more prevalent in Minnesota. This field research is identifying common issues affecting the performance of ERVs in Minnesota buildings and is developing protocols to optimize their performance. Since mid-July, project staff have been monitoring systems and collecting data at the five sites in the first phase of the project. Staff also performed more time-consuming and invasive measurements at each site in peak cooling season to augment the ongoing data collection. Staff are now synthesizing the information collected at all the sites, performing final analysis of the data, and issuing site specific recommendations. Recommendations will be implemented in early January followed by 6 more months of monitoring to observe the effect of the recommendations in both cold and warm weather. The next step will be to develop protocols for optimizing ERVs to achieve the expected savings.
Phase one showed that many buildings that can benefit most from ERV retrofits, such as schools and other public buildings, are often not designed and constructed with energy recovery in mind. Each site has a unique set of characteristics that impact ERV performance in unexpected ways. In addition, ERVs can have integration problems with other building controls, resulting in control related problems, poor performance, and frustration for facilities staff and building occupants. Phase two site selection is underway and will take into account the lessons learned in the first phase of the project.
Even when ducts are entirely within a building’s enclosure, air leakage from ducts waste energy by increasing fan power and discarding conditioned air. This research is characterizing the leakage of large commercial and institutional building duct systems and developing air sealing screening and diagnostic procedures. The project team has encountered many different types of duct systems including those with low and high rates of leakage and systems that can be sealed with varying efficacy. While there is a lot of variation in payback, there are similarities in the types of buildings and systems where cost-effective savings can be achieved. Project results will help determine guidelines for the types of buildings and systems that are good candidates for air leakage sealing, as well as expected energy savings from air leakage sealing in large commercial and institutional buildings. These guidelines may be incorporated into larger recommissioning projects and new construction, and could potentially lead to utility rebates.
The market share of condensing boilers has increased dramatically over the last several years, thanks in part to utility programs that provide rebates. Unfortunately, many of these newly installed condensing boilers only achieve a fraction of their expected energy savings. This field research is quantifying how operating conditions impact the installed energy efficiency of condensing boilers and is determining the potential for optimization through low-cost upgrades. Field monitoring at all 12 sites finished up this fall. The results confirm some of what the team expected to find, as well as a few surprises. One unexpected finding was the number of sites where addressing short cycling could increase the efficiency and the lifetime of the boilers. In most cases, this can be fixed by a simple change to the controls.
The team is now conducting an online survey to better understand condensing boiler installation issues and gain perspective on addressing these issues with CIP programs. The survey is geared towards trade professionals who deal with condensing boilers such as designers, contractors, manufacturers, utility staff, and facility owners and operators. A final report will be available in early 2015.
Tight exterior envelopes have become standard for single family homes, but these construction practices have not yet reached the multifamily sector. This research will determine whether the aerosol sealant method developed by the UC Davis Western Cooling Efficiency Center (WCEC) is a cost-effective way to reduce envelope air leakage in Minnesota multifamily buildings. The team began field testing in multifamily new construction this fall. A WCEC staff member traveled to Minnesota to work with CEE staff to seal six units, and then CEE sealed two more on their own. The sealing resulted in 71 to 94 percent reduction in leakage across all of the units, and some of the units were sealed as tight as possible for typical multifamily units. The initial results exceeded energy code, indicating that this may be an effective method for multifamily builders. The sealing also resulted in odor and sound transfer reduction, a major benefit for many multifamily owners. Given how tight the aerosol sealant method was able to seal the units, mechanical ventilation poses potential problems as units can no longer rely on air leaks for ventilation. This will also be an issue in existing buildings, and something the staff will continue to look for in their field work. The next step for the project is to recruit additional new construction buildings, and to begin recruitment of existing buildings. The project plans to seal 15 to 20 new construction units in two to three buildings before moving on to testing the sealing method in existing multifamily units.
In addition to this work assessing the aerosol sealant method, CEE continues to test and research air leakage of large building envelopes in both multifamily and commercial buildings. Watch this video of CEE’s recent work testing air leakage at a large commercial building.
*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.