Mitsubishi Electric “Interview with an Engineer” features MKK’s Ken Urbanek
VRF Zoning Technology Obvious Choice for Historic, Residential Projects
Engineering design and consulting firmMKK Consulting Engineers, Inc. (MKK)has been designing and engineering mechanical, electrical and plumbing systems for new construction, renovations and expansions since 1959. MKK has completed engineering projects in the contiguous U.S., Alaska and Antarctica, as well as an assignment at the summit of 14,000-foot Pikes Peak in Colorado. Mitsubishi Electric US Cooling & Heating Division interviewed Ken Urbanek, associate director of engineering at MKK, about the Greenwood Village, Colo., firm’s experience with Mitsubishi Electric CITY MULTI VRF zoning systems.
Mitsubishi Electric US Cooling & Heating Division (ME): Why did you initially specify Mitsubishi Electric VRF [Variable Refrigerant Flow] zoning systems?
Ken Urbanek (KU): After Mitsubishi Electric representatives in the Denver metro area first presented the system to us, it was a couple of years before we found a project we felt it would be suited for. We knew it would have to be a project with a client who was both looking to improve energy efficiency and willing to look at new technology. One of the first was for some barracks at Fort Leonard Wood in Missouri. Not only did VRF supply what the U.S. Corps of Engineers was looking for in its energy-efficiency goals, but it also lent itself to that type of dormitory environment, which had very specific zoning and needed individual temperature controls in each room.
ME: Have you recommended VRF zoning systems for non-residential projects as well?
KU: For a project with theDenver Department of Human Services,we worked on a two-story, 50,000-square-foot office building that was a unique opportunity. The client, an architect, is well known for pushing the envelope when it comes to energy goals.
ME: On that project, you used VRF technology in conjunction with another heating and cooling system.
KU: We used VRF systems for air distribution in all of the building’s open office spaces. But for the high-cooling loads in the computer and utility rooms, we used an integrated building technology called Under Floor Air Distribution, or UFAD. We had planned to use this UFAD for the whole project, because it lends itself well to the office environment — with a bunch of cubicles everywhere and a diffuser on the floor under each work station so each person can increase or decrease the airflow. The problem with UFAD, though, is that it’s relatively neutral air — not super cool or warm — so it’s not adaptable to extreme weather conditions. So the guy sitting in a cubicle can make himself comfortable, but someone with an office where sun beats on the windows, even in the winter, will be hot. We placed the VRF system along the building’s perimeter, so the heating and cooling in those spaces works independently of the under-floor system.
ME: Can you give us an example of a time when you chose a VRF zoning system instead of an alternative?
KU: We have selected the VRF system instead of geothermal at times. One example: We used VRF at a large maintenance facility for some of the new commuter trains that will be coming to Denver. It’s a big, four-story building with a lot of offices on the top floor. We wanted to go for LEED certification, so we looked at geothermal, but there was no space for a loop field, and we could get comparable energy efficiency with the VRF system.
ME: In what specific applications is a VRF zoning system the obvious choice?
KU: For a retrofit of an existing historical building, the VRF system lends itself well to squeezing equipment into small systems. Same goes for hotel rooms and residential apartments, and for administrative buildings with a lot of offices. We’ll start working on a 130-year-old historical building soon, and we’re recommending VRF because the system doesn’t need a boiler room, and it doesn’t need a chiller that needs a lot of maintenance.
ME: What advice would you give to an engineer who is thinking about using VRF zoning technology for the first time?
KU: Two things. First, do your due diligence. Several companies make VRF systems, but not all of their reps have the experience to really educate you about them and help you use them. Mitsubishi Electric has a very thick engineering manual. Find a rep to deal with who knows what that book says. Make sure he knows his stuff. And get to know these systems yourself. ASHRAE’s 2012 handbook also devotes a lot of space to VRF systems. It’s a great write-up. Second, let that rep help you. At MKK, we take a performance-based specification approach. We lay out where we want the terminals, how many, what the capacity of each one will be and how the refrigerant lines are put together. Then, we do a performance-based assessment with Mitsubishi Electric to make sure we’re leading the client in the right direction. That works out well.