On some magical occasions, everything goes just the way it's supposed to: an open-minded customer enters into a trusting relationship with a Design/Build contractor, and gives the contractor a free hand to create the best system for the application.
The results of such collaborations might justifiably be expected to be outstanding. In the hands of Kahn Mechanical Contractors, Dallas, TX, the results might even turn out to be spectacular.
Case in point: the JFO Group Office Building, Irving, TX. This 80,000 sq.ft., four-story building was constructed in the mid 1970s, when Tom Landry stalked the sidelines and Roger Staubach engineered improbable victories just down the road at the (then) state-of-the-art Texas Stadium. That era may have been a great time for pro football in Irving, but just as today’s players are bigger, stronger, and faster than their 1970s counterparts, today's commercial HAVC technology is smarter, more versatile, and far more efficient than that of the 1970s.
This facility served as the regional headquarters for General Motors until 2004, then sat empty for two years. In 2006, it was purchased by Jentera, LLC., for use as a privately owned office facility for family-owned business ventures. Jenterra performed extensive aesthetic remodeling of the space, but no significant mechanical improvements had been made to the chilled water cooling plant and air handling systems since the original construction.
"The mechanical systems were in serviceable condition, but the intended design and use of the building had changed dramatically since construction," says Josh Kahn, president of Kahn Mechanical Contractors. "Utility expenses and consumption were rising. The risk of equipment catastrophic failure all became extreme concerns for building ownership."
In addition, high humidity levels were causing comfort complaints from occupants and indoor air quality (IAQ) concerns. As a prior Design/Build Award winner and Contracting Business magazine's 2008 Commercial Contractor of the Year, Kahn Mechanical was the right company at the right time to update this building’s comfort systems.
How Trust Played a Part
Kahn had been performing maintenance on the 80,000 sq.ft, four-story building’s old HVAC system for a number of years. The trust built up over those years played a key role in the customer's decision to contract with Kahn Mechanical for the replacement of the system.
"Our prior experience as a Design/Build Award winner speaks to our experience and knowledge of facility life cycle analysis," Kahn says. "We have excellent credibility with this client from past experience, as well as a wealth of customer referrals from other Design/Build clients. In fact, each referral client shared stories of our Design/Build team exceeding expectations.
"Most importantly, we presented solutions to problems beyond the nuts and bolts. We avoided discussion of air handlers, chillers, and pumps, and focused on improving dependability, comfort, energy efficiency and lower cost of ownership."
Efficiency & Sustainability Up Front
Kahn’s project design included five key components:
- An extensive survey of customer requirements, mechanical design, and equipment selection.
- Life cycle analysis for modeling loads and energy use.
- Replacement of the central chilled water plant chillers, cooling towers, and pumps.
- Installation of new custom air handling systems designed to reduce indoor humidity levels and improve IAQ.
- Reconfiguration of the existing facility control system to properly sequence the central plant, the fresh air systems, and the new air handling units.
Equipment efficiency and maintenance sustainability were always in the forefront on this project. Kahn Mechanical delivered 250 tons of cooling to this facility for a total energy cost of about 190 kilowatts inclusive of the chillers, cooling towers, pumps, and air handling.
"We addressed the efficiency of this facility by using best- in-class equipment," Kahn says. "We selected McQuay frictionless, magnetic bearing, water cooled, chillers— which deliver an exceptional 0.363 kw/ton non-standard part load value (NPLV). The Evapco cooling towers reject 250 tons of waste heat with a paltry total fan horsepower of 12. We used ultra high-efficiency pump motors and blower motors served by ABB ACH550 variable speed drives."
There were some challenges with the instllation. The fourth-floor air handling units had to be moved in through a window of the exterior of the building, using a telescoping boom forklift. The third-floor units were moved in through an atrium window using the fourth floor sky bridge as a hoisting anchor.
Significant IAQ improvement came from replacing the improperly designed equipment. Kahn's team specified sloped stainless steel drain pans, antimicrobial coatings in the equipment, and properly designed cooling coils with sensible/latent ratios to properly treat the air. Lastly, large surface air filtration was designed to allow for higher levels of air filtration within the mechanical footprint. "Space humidity has fallen below 55%, and occupant complaints have all but disappeared," Kahn says.
The system's energy efficiency is monitored by a Tridium/Johnson Controls LX Energy Management System.
"This is without a doubt the most energy efficient plant we'’ve ever installed," Kahn says. "We designed a control system that captures the instantaneous energy consumption of every component in the plant. As we tune individual parameters we can see in 'real time' the impact to the entire facility in a snapshot. This is an amazing tool we're just beginning to understand, as a method for continuous improvement in control strategy."
"The reduction of our overall power bill is absolutely tremendous," says Tharin Robertson, facilities manager for the JFO Group Office Building. "In May of 2009 the power bill for our building was $35,000. For May of 2010 we’re down to $12,000."
Kahn Mechanical Contractors takes the approach that commissioning a project of this type is minimally a two-year commitment, in that it takes two complete cycles of the seasons to adequately adjust a mechanical plant.
Through the use of historical trending, areas are identified whereby the control algorithms and sequences can be tuned to obtain best efficiency at each operational point.
Next, the company discovers any improper assumptions that were made during each seasonal change, and adjusts the equipment and control systems accordingly to account for these changes. Any operational changes at the facility are discussed, and opportunities to further serve the client are investigated. Then, in the second year of seasonal changes, the changes are analyzed and additional adjustments are made as necessary.
The Price of Success: Constant Improvement
The opportunity to work on a Design/Build project with such an outstanding client proved to be wonderful but also a challenge to Kahn's team.
"This client placed extraordinary trust in Kahn Mechanical Contractors," Kahn says. "They allowed us carte blanche (within budget, of course) to do whatever we felt was in the best interest of the building owners. This was simultaneously an amazing gift of trust, and an awesome responsibility. In the end, the results exceeded the client’s expectations, and showed us that we continue to improve our delivery with each and every project.
"That’s the price of success," Kahn concludes. "As an award-winning Design/Build team, we want to not only be award-worthy, but to surpass our prior accomplishments."