David Seighthinks big. For his first-ever radiant job, the owner of mechanical contractor Mervac Plumbing & Heating, Windber, Pa., chose to lay out 8 linear miles of 3/4-inch PEX throughout a century-old 43,500 sq. ft. space powered by a commercial water tube boiler.
"We really jumped in feet first," Seigh notes.
While his company had plenty of experience over the past 15 years installing hydronic systems in light commercial and industrial spaces, his 31-member staff had yet to do a radiant job.
"In this part of the state, most of the radiant jobs are found in residential construction," Seigh explains. "We don't do residential work so we've just been out of the loop for most radiant work."
But they know a thing or two about piping a boiler and providing the comfort that only wet heat can provide. So Seigh knew he could tackle radiant when Mervac put in a bid for a radiant heating job for GapVax, a Johnstown, Pa., manufacturer of trucks used by industrial cleaning contractors around the world.
"Piping the boiler was no big deal," he adds. "And as far as the radiant system goes, it was just a lot of little jobs done altogether."
Less Visible ...Regardless of the sheer scale of even the most average commercial radiant installation, jobs like Mervac's represent what some term "the ugly kid sister" of the radiant market. While there's no shortage of coverage for residential radiant systems, commercial jobs rarely get much press.
"Most think of radiant as home heating," one manufacturer told us.
While there's no doubt radiant tubing shipments have grown at a steady clip during this decade, how much of this tally can be attributed to commercial radiant jobs is hard to come by. Tubing shipments aren't broken out by diameter sizes - and even if they did, size alone is no sure indicator of the type of application as it is for Btus and boilers.
However, the manufacturers we spoke to estimated that 15 percent of the tubing they sell winds up in commercial jobs. That figure certainly jibes with a new survey of Radiant Panel Association members.
"How big the commercial side of the market is has always been a question on my mind," says Larry Drake, executive director of the Radiant Panel Association. According to his new survey, 14 percent of the tubing responding RPA members installed last year was for commercial applications. Meanwhile, three-quarters of their work is for residential heating. (For the record, these figures are subject to change since as we prepared this story, RPA staff still needed to finish more number crunching before making the poll results official. "I think the numbers will probably hold pretty true as the rest of the results come in," Drake adds. Our numbers represent about a 15 percent return to the survey.)
... But GrowingThanks to the momentum gained by the residential radiant market, many manufacturers are more than optimistic about the potential for the commercial side of the business. "I wish the commercial market were bigger," another manufacturer says. "I think it's a large opportunity. Five years ago, we weren't putting in the residential systems you see today. Life was tough in comparison!"
According to one boiler manufacturer, approximately 25 million sq. ft. of conditioned space was heated by means of hot water radiant heat in 1992. By 1997, the figure shot up to close to 100 million sq. ft.
"The commercial market will be propelled by the growth in residential," one manufacturer says. "As more contractors get into the residential radiant installation, it naturally creates a sales force ready to take on the commercial market."
In order for the momentum to spread to the commercial side, manufacturers say the industry will need to educate engineers who specify systems, and placate skeptical property owners who may steer clear of a higher first-time installation cost without considering the higher life cycle costs of traditional hot air systems.
"Once you get past the first-cost hurdles and get a chance to address life cycle costs, the relatively simple controls and very low water temperature requirements make commercial radiant systems very cost effective to operate," one manufacturer adds. "There are plenty of applications - and I think better applications - for radiant heat in commercial property."
Traditionally, the heat output for a commercial space was simply geared to match the heat loss. And the distribution of forced air heat was so erratic that electric heaters were as common a sight on one side of the building as open windows were on the other.
For many commercial facilities with high ceilings and large doors that are constantly opened throughout the day, radiant is an excellent way to provide comfort. A slab installation in such a space provides the building with a tremendous heat sink to help control the comfort level.
"You only need to heat the bottom half," one manufacturer adds. "A forced air system would require air temperatures of, say, 70-72 degrees F. The same spaces can be heated very comfortably with a radiant slab at air temperatures up to 10 percent less due to the way occupants would be warmed."
To A TeeAll of which fits Seigh's job to a tee. "We seriously considered no other form of heat," saysMark Bucciwho supervised the project for GapVax. "A lot of the work we do requires our employees to get down on the floor. We were always in favor of radiant since this would provide the best comfort for our workers."
In addition, to rehab the space GapVax needed to re-do the floors anyway. (For more on the history of the building, see sidebar.) A freshly poured floor had the added benefit of providing a perfectly level surface for the fabrication process. GapVax produces about six trucks a month on average. The heavy-duty trucks are equipped with industrial vacuum equipment used primarily to clean up waste at power plants around the world. The Volvo cab and chassis roll out weighing 44,000 lbs. when everything's said and done as it makes it way down an assembly line of sorts.
To even out the large, pockmarked surface, a bed of gravel was laid down; next came a vapor barrier and the wire mesh for the tubing on top of that.
"Pulling the tubing is nothing compared to tying down the tubing," says project foreman Pat Hamonko. "Your body really takes a pounding when you have to bend down every 3 feet to tie it down." It took Hamonko's crew of six 2 1/2 days to layout the tubing. At 3 a.m. before the Fourth of July weekend, the crew awaited the arrival of the concrete subcontractors.
Due to the sheer weight of the trucks, GapVax needed to pour 6 inches of concrete on top of the tubing. Normally, contractors want the top of the tubing to be at least 2 inches below the surface. But that's not a problem with this design.
Seigh called on Burnham Radiant Heating Co. to help out with design. Approximate rules of thumb may suffice for a residential job, but commercial jobs need to be engineered, according to the company's manager of engineering Gary Hayden.
"I don't mean to say that anyone can do this," Hayden says. "But with proper design assistance, I think it's important to point out that there are plenty of heating contractors who have stuck with traditional hydronics who could also be installing radiant systems - no matter how big."
Designing such a behemoth heating system is like driving a semi: The worst thing the driver could do is come to a dead stop at a red light. He's much better off if he can coast through the lights and never stop.
Since low temperature water will run constantly through the slab, it will sit in 'idle' to maintain temperature," Hayden says.
The slab surface is designed to run at 73-80 degrees F, for a resulting room temperature of 60-65 degrees F - cold for a home, but right in line with ASHRAE guidelines for commercial facilities that require a lot of manual labor.
In addition, considering that the age of the building precludes any kind of accurate heat loss, the tubing layout includes tighter spacing around the perimeter of the space so the same water temperature kicks out more Btus. (Mervac did spray an insulation material on the old brick walls from floor to ceiling to offer some R-value.)
Concrete CowboysThe most harrowing experience came early that morning with the arrival of the concrete subcontractors. Over the advice of Mervac, the subs delivered all that concrete with six motorized "wheel barrows" that would have to be driven directly on the tubing. The first day's pour took 12 hours and accounted for about two-thirds of the space.
"You better finish up what's your responsibility, because the concrete guys just come in and cover it up," Hamonko says. "They don't want to wait around; their job is to pour concrete, and they're not concerned with what they pour it on top of. If you persuade them to use their rakes with the tines pointed up, you're in good shape!"
For the final pour several days later, the concrete contractors used what Mervac advised in the first place: A two-man crew operating from a pumper system that could spray the concrete as much as 10 feet.
To ensure a level surface, the concrete subcontractor also used a laser-guided screed for both pours. A consul-mounted computer maintains the grade with laser precision, and monitors the screed elevation at a rate of five times per second. The 8-foot-wide screed head is mounted on a 12-foot telescopic boom and can accurately level 100 sq. ft. of concrete in just one minute.
By the time this article is printed, GapVax will be about ready to fire up the project for the winter ahead. Meanwhile, Seigh plans on more radiant work. "I want to do more commercial radiant jobs," he says. "When word gets out about this job, I'm sure we'll get more of this type of business."