Fabric duct adds looks, comfort to converted bakery
Just ask officials from Dallas architecture firm Boka Powell, who were assigned the retrofit.
Hoover's wanted the currently vogue industrial style of interior design for their building. That allowed architects, interior designers, and engineers to retain many of the former Butter Krust Bread factory's authentic touches, such as exposed steel girders, 6-foot-square wall exhaust ventilator-propeller fans, the steel ceiling and other existing industrial features.
The result provides Hoover's and the one-story steel and masonry building's owner, Riverside Resources, an Austin-based commercial real estate developer, with a state-of-the-art, high-tech office building.
While the warehouse-style design strategy of exposing the 20-foot-high steel ceiling added to the space's aesthetics, it also presented an HVAC challenge for consulting engineer Thomas Alexander, a principal engineer with Talex Inc. of Austin, and Houston mechanical-electrical-plumbing contractor Encompass Inc.
Cooling hundreds of workers stationed at open cubicles in two large 30,000-square-foot rooms required strong and even airflow without drafts. Alexander chose fabric-duct air dispersion manufactured by DuctSox of Dubuque, Iowa. The system included 29 gas-fired Voyager Series rooftop units from Trane Co. in Tyler, Texas.
"There's absolutely no comparison between this HVAC system and the system in our old headquarters," said Sally Collier, Hoover's director of training and operations. "The airflow before was drafty and cold in certain areas, but now nobody even notices that the air conditioning is on, except for the fact they feel comfortable."
Adds Riverside Resources' project manager Carson Cross, "The HVAC design in our retrofitted building is really providing superior IAQ (indoor air quality) with no dead spots or air stratification in any areas."
Using over one mile of varying diameters of DuctSox's round TufTex high-throw fabric, the air conditioning is draft-free and evenly distributed. Thousands of 1-inch-diameter dispersion orifices were placed in a linear pattern at four and eight o'clock on the ducts, and spaced apart from 8 to 14 inches on center.
DuctSox's in-house engineering department designed the orifices' uniform diameter and varying patterns to meet Alexander's specifications for proper static pressure and airflow throughout different locations in the office areas.
"The high ceilings combined with a heavily occupied space created a problem of providing air flow that wouldn't be drafty or uneven as would probably be the situation with metal duct runs and registers placed every 5 or 8 feet," said Alexander.
Alexander's decision to use 29 rooftop units ranging from 3 tons to 17.5 tons helped space out the roof load according to structural engineering requirements, but it also presented an installation challenge to Encompass' Austin-based southwest division, which performed the mechanical, electrical and plumbing work.
The fabric duct arrived on-site via ground freight and was organized for installation by Encompass' three-man duct crew. The result was a myriad of duct organized by Alexander's designed HVAC zones consisting of 30 trunk lines ranging from 14 to 26 inches in diameter and dozens of branches ranging from 8 to 16 inches in diameter.