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By Barbara Knecht

Continuing Education Use the following learning objectives to focus your study while reading this month’s ARCHITECTURAL RECORD / AIA Continuing Education article. Learning Objective: After reading this article, you will be able to: 1. Describe the best time to deal with sound attenuation in air-handling systems. 2. Discuss appropriate uses for radiant heating and cooling systems. 3. Explain the benefits of underfloor air distribution.

An Australian television crew was recently filming an interview with the executive director of a New York–based not-for-profit housing developer in its flagship building in Times Square. Partway through the interview, which took place in a top-floor conference room, the cameraman yanked off his headphones to ask about the loud noise that suddenly started. It wasn’t sirens on the street outside. “It’s the AC unit coming on,” explained the director. “It’s on the roof just above us.”

Heating, ventilating, and air-conditioning (HVAC), as every architect and MEP engineer knows, are designed to work together to provide a comfortable environment, unobtrusively and cost-effectively. Of course, no one notices when the collaboration is successful, but no one can help but notice when it isn’t, especially if the thermal properties are inadequate or the system is noisy. Then cost-effective quickly turns into costly.

“If you have to retrofit after construction is completed, you are doing it in an occupied building on premium time. And if it’s a problem to the occupants, you can’t fix it fast enough. It is much more cost-effective to do it right from the start,” explains Paul Sampson, principal of Spaulding & Slye Colliers, a real estate services company in Boston and Washington, D.C. “We have made it a practice to incorporate acousticians as part of the design team in all our projects.”

Mechanical engineers and acousticians agree that, in most applications, it isn’t difficult to provide sufficient sound attenuation for building occupants. Still, one of the most common problems remains rooftop equipment placed over a sensitive space, which causes problems for the occupants and, quite often, for those in neighboring buildings. “The list of potential offenders is long,” says Anthony Pangaro, principal at Millennium Partners-Boston, which recently developed the Ritz Millennium Towers on the Boston Common. “Gurgling water in the distribution system, elevator noise, rooftop mechanicals, bypass piping, and heat pumps of all kinds are all on the list, but it’s relatively easy to deal with noise inside our own buildings. It’s much harder to deal with the noise from a rooftop unit, especially with the increased use of operable windows. We try to make sure that the most cost-effective solution for us doesn’t cause a problem for someone else.”

 

Three inverted domes mark Northeastern University’s Spiritual Life Center. Photography: © Dan Bib

“The most cost-effective noise control that you can buy is in the design phase,” says Carl Rosenberg, president of Acentech, a national acoustical consulting firm. “Noise control treatments are generally very inexpensive.” Acentech engineer Doug Sturz concurs: “We have learned that fixing a problem can cost five to ten times as much as attenuation during initial construction. We have also learned how to analyze solutions from the cost-benefit-risk standpoint. Not all solutions can be implemented within a project budget, and by prioritizing and analyzing the benefits of a solution against the first costs and the risk of a significant problem requiring mitigation, an owner can make an informed choice.”

According to Sturz and Rosenberg, problems often arise when a system that was acceptable in one application is carelessly specified again in the next. Replication seems cost-effective, but circumstances are rarely identical. In office-building construction—the most ubiquitous building type—volume purchasing can buy better sound attenuation. According to Tim Foulkes of Cavanaugh Tocci Associates, acoustical consultants in Sudbury, Massachusetts, “Rather than specifying a standard system, which is then shopped around for the lowest bid, some projects are committing to a product up front and then working with its manufacturer on a custom design to get exactly what is needed to integrate sound attenuation into the air-handling system.”