Spring 2014 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.
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 is a cost-effective way to reduce envelope air leakage in Minnesota multifamily buildings. This technology has been used to improve residential duct sealing for over fifteen years. A redesigned injection system has been developed for envelope applications. The process has the potential to be more effective and convenient than conventional methods for sealing ducts, because it requires less time and effort, and seals a larger portion of a leakage area more quickly. It can seal numerous, diffuse leaks; be used in existing buildings with finished surfaces; and provides real-time feedback during sealing, so technicians can determine when it’s no longer cost-effective to continue. It also offers the non-energy benefit of reducing air flow and contaminant transfer between units.
UC Davis is developing a protocol for the sealing process itself and methods to determine the impact of sealing. This includes using sound measurements to indicate the impact of unit to unit sealing. They’re also working on a method that puts fluorescing dye in the sealant so after completing work, a special camera can identify where the sealant ended up. CEE is developing complimentary field test procedures to measure exterior air leakage and that within the building. The two groups will collaborate to review the initial experimental plan and finalize site selection criteria. CEE will develop a recruitment plan and find sites in early stages of construction. Later this spring, a representative from UC Davis will train CEE staff on the sealing process and CEE staff will conduct the sealing in multifamily new construction buildings this summer.
Energy recovery ventilation systems transfer the energy from outgoing exhaust air to incoming outdoor air to reduce heating and cooling energy while meeting ventilation requirements. They 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. But according to a 2010 Minnesota Market Assessment Report, only 48 percent of systems operate properly immediately after installation, with an overall average efficiency of 42 percent. And very little field data is available on commissioning and recommissioning best practices for ERVs. This field research will identify common issues affecting the effectiveness of Energy Recovery Ventilation in Minnesota buildings and develop protocols to optimize their performance.
Project lead Josh Quinnell is working to identify test sites, and is prepared to screen candidates and interview building owners and operators. Site selection is based on a representative sampling of ERV systems throughout the state. The research team consolidated prior ERV research, including a market characterization study and observations from the PBEEEP program, to determine the characteristics of ERV systems in Minnesota buildings and what types of operational issues reduce their effectiveness. Control related problems appear to generate the majority of problems, because they’re sophisticated and don’t always integrate with other building controls, resulting in poor performance and frustration for facilities staff.
The energy use intensity for indoor pool areas is three times higher than most other areas within a building, and recommissioning programs rarely reach hotels and motels, which have about 40 percent of the indoor public pools in Minnesota. These indoor pool facilities present a number of challenges for energy efficiency programs due to their specialized equipment and inconsistent tie-ins with building automation systems, and because they’re often only a fraction of a larger building. The HVAC systems in pool facilities are complex and can easily use excess energy, but pool operator certification trainings focus almost exclusively on water treatment and pumping. All of these factors make indoor public pool facilities ripe for energy savings through improved recommissioning and operator training—as we’ve already seen in a number of individual facilities with improperly operating fresh air ventilation and energy recovery equipment.
This project will set the stage for realizing significant energy savings by developing guides for energy efficient operation and recommissioning of indoor swimming pool facilities and quantifying the savings achieved through their use. Project staff will survey 30 pool facilities, using site observations supplemented with interviews and measurements to determine they type of systems, temperatures of pool and air humidity level, and how each site runs its heating and ventilation. The first on-site visits will be in April with an early focus on school facilities. Discussions and summary data from fitness center and hotel chains with several facilities will provide a good indication of trends and expand information beyond what the team can collect during the inspections. Based on the survey's trend information, they’ll begin detailed studies of six sites representative of the variety of typical Minnesota commercial indoor pool facilities within the next few months.
This white paper will characterize 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 tells users their expected energy savings after switching to a heat pump water heater, quantifies its effect their space conditioning load by reducing cooling and increasing heating, and plots how it would affect their energy consumption and peak load. The team is also developing a calculator for utilities that will demonstrate the effects on peak usage if X% of their customers switch to heat pump water heaters, using Minnesota average values and usage. The results are a good calculation of the ranges of expected savings, but if utilities need fine details, more research is needed.
Besides demonstrating the Innovation Exchange’s capacity to develop tools, the app helped hone in on the variables that impact final energy savings and peak reduction. For example, a homeowner inputs the number of people in a household, the type of heating and cooling system, and where in Minnesota they live. While it’s helpful to define these fields before developing the app, building the app helped define necessary variables. While coordinating the app’s design was a challenge the first time around, its graphics will help with presentations and webinars. Look for the calculators and final white paper on our website this spring, and stay tuned for a webinar of the results.
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 will quantify how operating conditions impact the installed energy efficiency of condensing boilers and determine the potential for optimization through low-cost upgrades.
Project staff have completed set-up and are collecting data at 12 sites that represent the common variety of commercial buildings with boiler systems. The preliminary results show that for many of the sites the return water temperature is brought down to 130F or lower (the optimal for condensation/efficiency by the time the outside temperature rises to 35°F, which suggests these boilers are achieving higher efficiencies for more than half the heating season. Short-term monitoring of stack gases has also been carried out for seven of the sites. So far, this monitoring suggests that the potential drop in efficiency at low firing rates is much less prominent than was feared from preliminary information from boiler manufacturers and their representatives. The stack gas monitoring results also suggest that there may be greater potential for energy savings from boiler tune-ups than initially expected. The project team will also begin systematic surveys of trade professionals to evaluate the potential structure and benefits of CIP program strategies that might better optimize the installed operating efficiency of commercial condensing boilers in Minnesota.
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. Project staff completed system assessments, analyzed measurements, and created recommendations for 18 multifamily buildings. This included recommendations for apartment central exhaust systems, hallway supply ventilation, and garbage chutes. Seven of the buildings with central exhaust ventilation in the units were over-ventilated and those have potential for retrofits to reduce energy. Four of the buildings should increase ventilation will see an increase in indoor air quality, but no energy savings. There were no recommendations for one building and six did not have central ventilation systems. The research team is compiling a table to summarize the key characteristics of each type of system, which they’ll use to identify the best opportunities for energy savings, and select buildings or systems that would be good pilot projects (representatives of other situations that the study found and would provide good energy savings). They’ll retrofit those buildings, document the effect on system, and confirm energy savings estimates.
It’s difficult to collect accurate airflow measurements, so the team had to use a variety of techniques. This is time-consuming, so project lead Dave Bohac concluded that an initial screening for potential energy savings should come before the more thorough (and expensive) assessment. If adapted into an energy program, assessment for buildings without savings potential could be a paid service for owners concerned with ventilation and air quality. And from a training standpoint, it’s relatively easy to train for screening, but auditors need additional experience and capabilities to conduct a full assessment.
Duct leakage can waste energy 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.After refining a tracer gas system to measures air flow rate, the team has established and verified a process to obtain duct leakage measurements. They tested a duct branch in a large commercial building that had 23 percent leakage when the system was operating in max cooling flow rate. The team’s pressure leakage tests came out slightly above that value. They’re partnering with a local contractor (Trinity-Vac) to measure the impact of using conventional duct sealing methods for that branch. Trinity-Vac also has purchased robotic equipment that is placed inside the ducts to seal leaks. That equipment will be used for future tests. The team will also monitor the work by another Minnesota contractor trained in aerosol sealing for potential test sites. Over the next few months, the project team will recruit test site buildings, complete air leakage measurements of existing systems before and after air sealing, and develop schemes for energy savings estimates.
According to contractor interviews, some customers are interested in duct sealing but hesitant to commit without documented performance and reliable estimates of energy savings. These measurements are currently unavailable, but project results will provide unbiased documentation. In addition to reducing energy use, duct sealing can help address situations of insufficient air flow capacity. For example, fume hoods/bathrooms may have insufficient flow that could cause an air quality or hazardous situation. Low supply flows can also result in an inability to heat or cool a space. Duct sealing can improve the system’s capacity and performance, improving comfort and potentially indoor air quality. While the focus for this project is to document the impact of duct sealing, UC Davis is developing a system to measure duct flows that contractors will be able to use for their own measurements of duct flow and leakage. CEE will share project findings and participate in their informational meeting later this spring.
*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.
Image credit: facilitiesnet