When it comes to specifying ductwork, sheet metal contractors are more concerned with meeting code requirements, preventing leakage and overall performance than whether a product is considered “green.”

And when they’re installing ductwork, it’s most likely to be rectangular or spiral than other types - and it’s probably going to be metal.

Those are among the findings of a study on ductwork systems recently completed by Clear Seas Research, a division of BNP Media, parent company of Snips.

Clear Seas Research sent e-mails to 4,313 Snips subscribers to gauge their familiarity and purchasing with various ductwork products, including liners and accessories, and the state of business in their communities. A statistically significant 288 responded.

Of those who completed the entire survey, most have a long history in the industry. They have been involved in the selection, specification and purchasing of ductwork for an average of 22 years.

Important factors during selection/specification

Contractors consider system performance to be the most important factor when selecting or specifying ductwork systems, followed by code requirements and system leakage.


When it comes time to select or specify duct systems, respondents said system performance, code requirements, system leakage and indoor air quality are the most important factors considered.

Price is less important to many contractors; only 38 percent rated it very important, far below other criteria such as performance or meeting code requirements.

The growing movement to design environmentally friendly HVAC systems, commonly referred to as part of green building, is slowly being embraced by Snips readers. Only 13 percent of contractors surveyed said a product’s suitability for green building was very important; 35 percent said it was not important at all.

Items necessary when selecting/specifying ductwork systems

Metal ductwork is considered to be the most important item when selecting or specifying ductwork systems. Also important are grilles, registers and diffusers, duct connectors, air controls/dampers, and duct insulation.

A number of studies have made predictions on how much of the U.S. rectangular duct market would be gobbled up by spiral duct by now. In 1998, a study commissioned by the Sheet Metal and Air Conditioning Contractors’ National Association predicted spiral would have 31 percent of the U.S. duct market by 2003 (See “Survey says,” June 2003 Snips). However, a 2002 update revealed it fell short of that goal, topping out at 29 percent. The study also said spiral might eventually hit a plateau where additional market share would be tough to find.

The numbers from Clear Seas Research were similar: round or spiral ductwork accounted for 29 percent of the work among those surveyed, with the vast majority - 61 percent - of projects using traditional rectangular ducts. Flat or oval ductwork was used only 4 percent of the time.

Ductwork specified

Nearly two-thirds of survey respondents use rectangular ductwork and over one-fourth use round/spiral ductwork systems.

Types of Ductwork Specified

Metal ductwork is the most commonly specified of all ductwork systems. Non-metal ductwork systems are specified in only one-in-10 projects.

Type of ductwork specified

Rectangular ductwork is most often used in hospitals, hotels, and government/municipality/military buildings. Rectangular ductwork is least commonly used in manufacturing facilities/industrial plants and warehouses.

Round/spiral ductwork

Just over 50 percent of contractors specify round/spiral ductwork for manufacturing facility/industrial plants and warehouses, while slightly under 50 percent specify round/spiral ductwork for supermarkets/convenience stores, restaurants, and retail stores.

Employment levels

Respondents believe employment levels are currently slightly worse than they were 12 months ago. Respondents also believe there will be little change in employment levels over the next 12 months.

Business conditions

Survey respondents believe that in the next 12 months, business conditions will be slightly better.

Location, location

Contractors are most likely to use rectangular ductwork in hospitals and hotels (82 percent), government or military structures (79 percent), and offices and commercial buildings (69-70 percent). They seldom put it in warehouses or manufacturing facilities. That’s where you’ll most often find spiral duct, where 66 percent of those who answered said they installed it.

The contractors who answered the survey aren’t currently doing a lot of work with non-metal or fabric duct. Only 11 percent of their work involves specifying non-metal ducts, and just 2 percent of work involves fabric, demonstrating it is a small niche.

Contractors who received the survey were also asked about business conditions and employment levels. The largest number, 37 percent, said employment levels were slightly lower than a year ago. And 41 percent said they expected them to stay at current levels.

For reprints of this article, contact Jill DeVries at (248) 244-1726 or e-mail devriesj@bnpmedia.com. The full Clear Seas Research study, including contractors’ brand preferences for ductwork products, is available for purchase. Contact research analyst Farah Shammami at (248) 786-1630 or e-mail shammamif@clearseasresearch.com for information.