Facilities (Campus Spaces)

Cool It

HVAC

PHOTO COURTESY OF LEBANON VALLEY COLLEGE

No matter the weather outside, your students, faculty and staff expect their facility interiors to feel comfortable. But nothing makes you sweat like opening a huge energy bill. To help balance thermal delight with reasonable costs, College Planning & Management looks at two ways, one simple and one futuristic, to keep everyone cool.

The Future Is Now

Variable refrigerant flow (VRF) is a relatively new technology here in the U.S., but it’s old news in most of Asia and Europe. Developed in Japan in 1982, the technology is described by a report by the Pacific Northwest National Labs for the General Services Administration (GSA): “VRF HVAC systems include two major parts, a compressor unit and multiple indoor fan coil units. The compressor unit, typically located on the roof, cools and heats refrigerant connected through piping to condition the building.”

The technology has a lot going for it. The system components are modular, small and lightweight, which means they can be installed without a crane. As the compressors are often installed outdoors, they do not require their own machine room. VRF can be zoned and controlled to provide heating and cooling to different parts of a building at the same time. Maintenance is as simple as cleaning the coils and changing the filters.

VRF provides a great solution for old buildings. Miami University in Oxford, OH, chose the technology when updating the HVAC systems of two of its oldest buildings: Elliott Hall, built in 1825; and Stoddard Hall, built nine years later. The two residence buildings were updated to include VRF in 2011.

“Renovation of any historic building is a complex undertaking requiring a balance between the original architecture and modern building systems,” says Alec Carnes, PE, CEM, LEED-AP BC+C, senior principal, Heapy Engineering, in a case study provided by Mitsubishi Electric. Architectural integrity was maintained in this case by housing the indoor units in custom cabinetry.

The GSA is also interested in VRF technology for its stock of older and historic buildings. “VRF is well suited to retrofit applications in older buildings because it can be added on to or replace existing equipment in limited space, where there is currently limited or no ductwork. VRF may be the least expensive option in some of these cases, or may offer a reasonable payback relative to other options,” says the report.

New buildings get the same benefits from VRF as old ones, with some added perks. “Because VRF doesn’t require ductwork you get more ceiling space,” explains Kevin Miskewicz, senior manager, commercial marketing, Mitsubishi Electric US, Inc., Cooling and Heating. That added space could translate into taller, grander rooms or even an extra floor for a new structure.

Energy Savings

The biggest advantage of VRF is, of course, energy savings. Miskewicz estimates that the technology is 25 percent to 30 percent more efficient than traditional HVAC systems. That estimate is in line with the GSA report. Part of that savings comes from the system’s controllability.

That was the case in The Suites on Paseo, a student housing complex in San Diego.

Designed to serve students attending San Diego State University, The Suites is composed of three adjoining buildings totaling 98,000 square feet. The space houses 287 students and was awarded a LEED Silver certification.

Michael Bigelow, LEED certification specialist and owner of Bigelow Energy, LLC, Las Cruces, NM, worked on the project. Bigelow was wowed by the technology. “The technology is impressive for its energy-conserving design,” he said in a case study. “Instead of the fans running 24/7 like a conventional HVAC system, they run only when students call for cooling or heating.”

When simulating outcomes as part of the LEED certification process, Bigelow found significant energy savings. “Without the onsite generation from solar PV and fuel cells, our design was 32 percent more cost efficient than the baseline,” he reports. “When we look at just the cooling system, including the fans, the system provided a 40 percent annual kilowatt-hour savings.”

Of course there are downsides to the technology. The GSA states that there is still uncertainty in estimating savings. Finding multiple designers and contractors with VRF experience may be difficult in some parts of the country. Finally, initial costs for VRF may be higher than conventional HVAC. “Greater variation in costs caused by different building characteristics is found in the retrofit market and ranges from VRF systems being less expensive to prohibitively more expensive than other choices,” according to the report.

Simple Maintenance

So what if you’re not ready for VRF but you still crave savings? Rob Martin, associate category manager, Kimberly-Clark Professional, has an easy solution. “Change your air filters.”

Martin reports that filters should be changed every 60 to 90 days, but some facility managers push that to every six months. The result is a buildup of dust and indoor air pollutants that forces your HVAC to work harder. “It may be easy to cut filters as a line item, but if you make your HVAC work harder you’re going to see an increase in energy use,” he says. Because of the complexity of the system, Martin couldn’t put an exact number on how much of a gain to expect.

Airflow is measured using a scale called pressure drop. A dirty filter is the most common reason for an excessive pressure drop. Ironically, filters become more efficient at capturing particles as time passes; i.e., the buildup of particles on a filter enables it to capture a larger percentage of particles of all size ranges (a fact known by HVAC companies and facilities managers). However, as a filter becomes more efficient at capturing particles, it increasingly restricts air movement through the filter. This restriction is measured by the pressure drop from one side of the filter to the other; more restriction would be characterized by a larger pressure drop. In most HVAC systems, a dirty air filter will reduce the volume of air moving across the coils, reducing system efficiency and resulting in the compressor running longer, thus consuming more energy… and raising your energy bills. So changing your filters saves money.

But not all clean filters are alike. Filters are rated using a scale called the minimum efficiency reporting value, or MERV. MERV 8 is the most common filter for commercial interiors. These filters trap mold, dust, pet dander and more. Better filters can offer the protection of MERV 8 with a lower pressure drop. “The pressure drop of standard MERV 8 filters can generally range from 0.27–0.29 inches,” explains Martin. “But with higher-capacity filters that have higher media surface area that number can drop to a range of 0.215–0.225 inches.”

That can help you breathe easier and keep your cool.

This article originally appeared in the June 2015 issue of College Planning & Management.

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