A quiet revolution may be taking ductwork where it’s never gone before.

Several of the major duct producers are changing the face of the industry, taking assembly time out of the jobsite and introducing products in an area that has never been known for high-tech changes.

Is this just marketing hype, or is the important business of moving air in our buildings really changing?

Lindab Inc., a multinational company with more than 2,000 employees based in Sweden (its U.S. operations are headquartered in Stamford, CT), says it is intentionally shaking things up. It claims its “SPIROsafe” rubber-gasketed, round spiral ductwork goes together much quicker in the field, justifying its 15% or so higher initial cost.

At an open house held for contractor customers and distributors at a new plant in Portsmouth, VA, the company invited two teams of assemblers to compare its system with a competitor’s. The results showed far less time to assemble the Lindab products.


The company’s director of product development, Larry Sunshine, said that approximately 70% of the cost of ductwork is in labor.

If you can save half of that by skipping such steps as using tape and mastic to seal a duct, the higher initial cost for materials is a wash, he said.

Ductwork comes in three varieties: round, oval, and rectangular. The latter accounts for some 65% of the market.

It is still the industry standard — relatively cheap and easy to produce in the field. Most architects and building designers like it because it takes up less room; to move as much air, a round duct must be slightly larger.

A conversion chart, rectangular to equivalent round, for example, shows that a 20- by 20-in. rectangular duct would translate to a 22-in. round duct and a 40- by 40-in. rectangular duct would require a round duct of almost 44 in.

Part of the decor

But round and oval are being used more often in exposed applications, which are catching on.

Starting with sports arenas, then on into restaurants, and shopping malls, many decided to simply leave the ductwork exposed rather than trying to cover it up with a false or drop ceiling. Paint the stuff and it can actually look quite attractive, part of the building’s interior color scheme.

However, using exposed duct often means an uninsulated ceiling, which is prone to increased heat loss and higher energy costs.

Competitors concede that Lindab is stirring things up and may deliver a good product. But they are stirring things up a bit themselves.

More new systems

Several new products are out that are changing the way ductwork is being specified and assembled.

Eastern Sheet Metal, Cincinnati, introduced a spiral pipe in 1989 and is working on a quicker-connect duct-sealing system of its own. Ductmate and The Duct Connection, among others, also have quicker connecting systems out.

AccuDuct is another company which has stirred things up, this time with its popular AccuFlange connectors, marketed by AccuDuct in the West and by SEMCO in the East.

The system has been out for three or four years, according to AccuDuct’s Jeff Hermanson.

The AccuFlange is also a labor saver, he said, because it has a “non-slip-joint” and “gets rid of the guy in the back pushing it into place.”

Hermanson said these are indeed exciting times in the duct industry. Typically, 64% of ductwork is rectangular, with about 30% round and 5% oval. But it’s the 5% oval sector that is growing, he said, and “creates a huge niche for us.”

Oval ductwork is quicker to insulate, he added, and requires less insulation material.

Wayne Custer, United McGill, Groveport, said Lindab has a good idea, and provides a good product — but with limitations.

U.S. manufacturers like United McGill and subsidiary McGill Airflow have also been helping to take the labor cost out of jobs for many years now, beginning with “manifolding” for the past 20 to 25 years. This is a trend that has to do with including the various fittings and shipping the ductwork as a system ready to connect in the field, almost like an erector set, according to Custer.

Plumbers have been pursuing this tactic with water connections, and it has saved time for them as well.

But overall, building designers in the United States tend to still rely on many non-standard duct sizes — assuming the contractor will be able to come up with the necessary sizes and fittings, rather than relying on standard sizes.

United McGill’s strength is being able to supply whatever the contractor needs, including round, oval, or rectangular duct. Custer said that United McGill will enter the spiral gasketed market by the end of this year.


Lindab says its SpiroSafe spiral ductwork goes together easily, one piece slipping inside the other — with little effort.

In the field, you can rotate the duct according to need, like connecting a child’s Lego® set.

When you have the duct where you want it, it’s a quick matter of installing four sheet metal screws to hold it in place. The rubber gaskets seal out air and help to control indoor comfort levels and indoor air quality, while reducing energy costs and noise.

No additional sealing is required, the company said; no mastics, no tapes, no more labor or waiting for the mastic to cure before it properly seals.

Ductwork can be manufactured by contractors at their shops or in the field. Manufacturing has generally been done on a regional basis, since it costs in both time and money to ship a product which is bulky and, after all, mostly air. Ductwork can also be easily damaged in shipping and handling.

Watch your toes

Duct manufacturers also have to be careful they don’t compete with their own customers. They want to supply ductwork, but have to be careful they don’t displace the many fabricators who use their products.

It will be interesting to see how many contractors begin to buy ductwork directly from manufacturers, several sources said.

Many small fabrication shops may feel threatened, if not immediately, then at some point down the road. Many installing contractors can move workers back and forth freely from the field to the shop to help balance their work load and maintain hours, something they wouldn’t be able to do if they eliminated their in-house fabrication shops.

Some contractors may prefer to bid a job with more labor and less material in order to keep their workers gainfully employed; however, if they lose the bid this strategy is immaterial.

Steve Sutton, business representative for Sheet Metal Workers Local 80 in Detroit, said loss of hours for his workers is a fact of life.

“We’re down to 1,500 or so workers where we used to have 2,000 to 3,000,” he said. “It’s unfortunate, but you can’t stop technology.”

The upside is that everyone is busy these days, thanks to the continuing economic boom — no one is sitting around on their hands waiting for work.

Mark Poole, project manager for MJ Mechanical Services, Buffalo, NY, said he is sold on the use of Lindab products. He laughs and says it was a simple idea with a million-dollar payoff, “like the pet rock.”

His company has been using these products for more than a year now. “It goes together smooth, just like they say, and it’s structurally sound. You can’t beat it.”

He said the product came in handy especially on a recent $1.2 million job installing ductwork for a dry iced tea mix plant where they couldn’t afford any duct leakage, either moisture or contamination. He said it also works great for exposed ductwork.