In recent years, energy efficiency ranked highest among the concerns for commercial HVAC clients. Then came the coronavirus pandemic, and IAQ moved to forefront. Energy efficiency still remains a major issue for companies trying to control costs and meet sustainability goals. Unfortunately, better IAQ often means sacrificing some energy efficiency. The good news is that manufacturers offer solutions that can make both these goals compatible.
Lauren Brust Moss, NORESCO director of sustainability services, explained during a Carrier-sponsored webinar that building owners and operators are seeking ways to balance occupancy, energy, and health while building trust. They know this is what it will take to attract and retain tenants, as well as bring employees back into the buildings.
“COVID had caused an immediate shift to look at the health of the occupants,” Moss said.
BACK AND BETTER: Schools have been among those investing a lot in improved IAQ. Systems upgrades done for that purpose also help in other ways. (Courtesy of Modine)
But energy costs remain a concern, especially for building owners who may have lost rent revenue during the pandemic and are now seeking new lessees in a competitive market. Moss recommends that any IAQ assessment include an assessment of the associated energy costs.
One of the main requests from building owners these days is increased filtration. In the past, the goal of HVAC was usually to protect the equipment, not the people. Now, higher filtration is seen as a way to combat virus spread. That problem is that it also makes the rest of the system work harder.
“Think of how much more energy it takes to breathe through the masks we’re all wearing these days,” Moss said.
Higher MERV filters also need more changeouts. Of course, clogged filters are only part of the system build-up that makes it work harder and use more energy. Moss points out that people worry about changing out filters but ignore dirty coils and controls that are out of calibration. An overall maintenance strategy can help reduce energy use.
Outside Air Brings In Other Issues
Richard Boothman, North American sales director for Modine Manufacturing Co., said the main concern for his clients right now is a safe reopening. That said, he is hearing more questions about the energy tradeoffs. There are many ways to increase IAQ without too great of an energy cost, Boothman said. One of these is increasing the amount of outside air via dedicated outdoor air systems. This allows some rooftop units to provide more ventilation while others provide comfort.
“In an engineer’s view, decoupling is a strong trend,” Boothman said. “It’s been around for a long time.”
Another option is an outdoor air economizer, he said. This controls the heating and cooling needs of a building by adjusting the mix of outdoor and return air, rather than doing so mechanically. Boothman also said clients are looking at modulating compressors, which decrease energy use by reducing the cycling of HVAC units.
There are typically two primary strategies used to minimize the impact of ventilation on energy use for commercial rooftop units, said Kevin Stockton, senior product manager for Johnson Controls Inc. One is demand-controlled ventilation (DCV), where a system matches the introduction of fresh air to the actual occupancy of a space. However, Stockton conveyed that during the pandemic, this benefit took a back seat to the need for increased ventilation rates to fight the virus, along with CDC recommendations to that effect.
The other typical solution is energy recovery wheels (ERWs). ERWs, or counter-flow heat exchangers, do not limit the amount of fresh air brought into a building, Stockton said. Instead, ERWs simply transfer energy between an exhaust (indoor) airstream and an incoming fresh airstream to precondition the incoming air, making it closer to the desired indoor temperature and humidity conditions. This entirely passive process can provide significant energy savings and can be used in process-to-process, process-to-comfort, and comfort-to-comfort applications.
Investments In IAQ, Energy Use Reduction
Industry experts foresee a continued interest in IAQ even after the pandemic ends. Other events, such as last year’s Western wildfires, made people more aware about all they are breathing in, not just germs. Moss said there are even studies that show better IAQ improves cognitive ability. This makes a complete HVAC solution crucial, Stockton said.
“While the introduction of fresh air to an indoor space can provide immediate benefits, it is energy intensive,” he said. Therefore, increasing ventilation alone won’t solve every air quality challenge. In fact, the EPA estimates the concentrations of some pollutants are two to five times higher in outdoor air than indoor air.”
Dust, dirt, pollen, smog, and other irritants are just a few potential contaminants that can cause or otherwise exacerbate existing respiratory issues, allergies, asthma, headaches, and other illnesses, Stockton said. IAQ products can clean indoor air and maintain ideal humidity levels to help reduce irritations and improve occupant well-being through solutions like germicidal UV-C lights, pre-filters and final filters, bipolar ionization, and humidification/dehumidification.
The good news is that the HVAC industry can move toward technologies that deliver both improved IAQ and energy savings. For one thing, some of the IAQ upgrades taking place in buildings across the country involve replacing older units. This means they could use less energy and will definitely improve comfort, Boothman said. Moss said eventually the IoT will allow buildings to adapt their usage. This means setting levels for comfort and ventilation that match the number of occupants actually in them, rather than an estimated number.