Let there be light

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Natural lighting is a key component of “green” building. But many owners of metal buildings, burned in the past by skylights that yellowed and whose seals became brittle, have instead gone without.

Now, however, advances in technology and performance are bringing skylights back to metal buildings. As a result, say manufacturers, owners can enjoy the benefits of natural lighting — backed up with warranties.

A number of skylight manufacturers have moved beyond fiberglass to alternative materials including polycarbonate or polyvinyl chloride (PVC).

“Polycarbonate is the next generation after fiberglass. It’s virtually unbreakable and it stays clear,” says vice president Tami Churchill of AmeriLux International, DePere, Wis., a maker of polycarbonate sheeting and PVC products, aluminum extrusions and steel tubing and coil.

Bruce Nystrom, president of MWI Components in Spencer, Iowa, says, “The popularity of polycarbonate skylights has grown greatly. The material has a much greater life than fiberglass. And the warranties that can be offered are important to people.”

MWI makes a variety of products for the post-frame industry and is a distributor of Marlon CS Longlife rooflights and Marvec PVC Sheets.

“Skylights have always been popular in silos, but the emphasis on saving energy has made more people think about using natural light rather than a light fixture,” adds Jason Dunn, who directs sales and marketing for H&F Manufacturing Corporation, a producer of plastic siding, roofing and louver panels based in Ivyland, Pa.

Major Industries in Wausau, Wis., manufactures translucent, glass, polycarbonate and acrylic skylights and translucent curtainwall systems. Marketing manager Mark Mitchell hails the availability of fiberglass alternatives but cautions against the idea that any single material is the best solution for all applications.

“We stress to our customers that their focus should be on how the building will be used, so that they can choose the right product,” he advises.

Evaluating the options

Because metal builders are most familiar with fiberglass skylights, Nystrom says, “It’s taken awhile to get polycarbonate skylights introduced and for builders to use them. Part of the reason is that when polycarbonate first came out, it was two to three times more expensive. Now acceptance is greater and the price has come down.”

Over time, builders are literally seeing the benefit of new materials that resist yellowing from exposure to the sun’s ultraviolet (UV) rays.

“In the past, UV protection wasn’t state of the art,” admits Churchill. “But because of advanced processes and technology, it’s much improved today.” AmeriLux, for example, guarantees its polycarbonate skylights won’t lose more than 6 percent of their light transmission per decade.

Being green, though, can mean striking a balance between options. Polycarbonate panels offer an R-value of only 0.84, Churchill allows, but skylights made of the material can potentially provide the energy savings of natural lighting for the life of a metal building — and then be 100 percent recycled when the structure is retired.

“Polycarbonate can be made into everything from CDs to two-liter bottles,” Churchill says.

Deciding how much of a good thing is optimal also can involve trade-offs.

The right ratio of skylights to roof area, Churchill advises, “depends on how much light the customers want. I’ve seen builders construct entire roofs made with the polycarbonate skylights. But sometimes the number is dictated by building codes.”

Another determining factor is R-value. The value of every skylight product will be different, explains Dunn. It depends on the thickness of the panel. Builders can boost insulation by installing panels with larger thicknesses than structurally required.

Manufacturers also have stepped up with products designed to increase R-value, such as an insulating multiwall panel with flutes in the middle, a product that is offered by H&F Manufacturing.

“Application and R-value should be considered in order to choose what’s best for your local climate,” Dunn advises. “Skylights do save energy by cutting down on electrical lighting. But it’s important to keep cooling costs down, too. Sometimes a multiwall panel is a better option for energy efficiency.”

Before a metal builder orders any skylight product, Dunn adds, “Check the spanning capability, warranty, impact strength and UV protection for the corrugation and thickness you need.” Information and recommendations regarding specific applications should be available from the distributor who sold the product.

Looking to the future

Nystrom notes that because environment affects plastics, builders should ensure the skylights they choose are suited to the local climate and the building’s intended use. “You should install skylights that will last as long as the steel roofing, provided that no harsh chemicals are used on the panels,” he says.

For example, polycarbonate skylight panels are now popular for agricultural structures. “Because many of these metal buildings are remote, it’s not as easy to have electrical lighting. So the greatest advantage of the skylight is making use of natural lighting,” Nystrom points out. But owners of agricultural buildings should also be aware, he continues, that “the harsh environment created by livestock causes more of an impact on the skylights than does the climate.”

On the other hand, states Churchill, “PVC interior liner panels work well in applications like dairy parlors or hog barns because the material is highly chemically resistant. The surface won’t be affected when they’re washed off.”

Even if skylights are included as part of a pre-engineered metal building package, Churchill urges builders to know what they are getting. For one thing, knowledgeable builders can better sell the benefits of skylights — and of fiberglass alternatives — to their customers. For another, builders who do their homework can learn about custom options. “We have standard stock which matches the common corrugations of metal panels,” she explains. “But we can also accommodate special requests for unique corrugations.”

Along with such customization, builders now enjoy other choices. “It used to be that clear was the only option,” Nystrom reports, “but now manufacturers offer skylight panels that diffuse light. The choice is often used for equestrian buildings in order to avoid intense bright spots on the floor. And other additives have been developed that have a reflective value so that the panel reflects heat but allows light.”

When it comes to installing today’s polycarbonate panels, builders must learn to work with the properties of the material. “Polycarbonate expands and contracts at a much greater rate than steel when temperatures change,” Nystrom says.

Because a 10-foot sheet can expand as much as a quarter of an inch, says Nystrom, “We recommend that you oversize the fastening holes. Improper installation can lead to cracking and leaking. And though fiberglass doesn’t expand as much as polycarbonate, it’s generally more susceptible to cracking. In any case, because expansion and contraction issues multiply the longer the panel, we advise builders to stick with shorter lengths.”

Builders should always make sure, Nystrom continues, that “you understand how the manufacturer wants you to install the panel.”

That’s important, Dunn agrees, because product warranties can be voided if a panel is improperly installed. Still, he believes proper installation is well within the capacities of qualified metal builders. “It’s reasonably uncomplicated to those used to installing metal siding and roofing panels,” he says.

A range of materials

Though polycarbonate panels might be the best choice for some metal buildings, Mitchell of Major Industries says other materials — including glass and fiberglass — remain good options for many applications.

“For instance, a manufacturing facility will have different concerns than an office building where employees are staring at computer screens all day,” he observes. “Some translucent panel options do better at cutting down on glare and hot spots than others. Or if the skylight is for a more transient area, glass or acrylic can be a very attractive option.”

Creating an aesthetically pleasing building can put more money in the owner’s pocket. “There have been a lot of studies that have shown how daylight can assist in increasing retail sales,” Mitchell relates. “People feel more comfortable in those spaces, so skylights are becoming increasingly popular in schools, too.”

In addition, Mitchell says, “Places like wastewater treatment plants have employees who work primarily during the day. So daylight can be used instead of keeping lights turned on all day.” Savings can be substantial in sections of the country where utilities charge peak-time rates.

Then, too, “For areas where there’s a lot of sunlight coming in, and you’ve got to deal with solar heat gain, we stress the translucent side of our product line,” says Mitchell. “That’s because, when you have clear glass skylights, it is difficult to control how much light is coming in. And that can wreak havoc on HVAC systems.”

On the other hand, Mitchell continues, “Solar gain isn’t as much of a concern for northern climates — where the big concern is thermal performance.” And in some cases, he notes, “the owner’s needs might even require venting to the outside. So the best solution could be a combination of translucent and glass products.”

Manufacturers of custom daylighting systems work with architects and structural engineers to ensure that the system meets local code requirements and can be adequately supported by the roof.

“We have an in-house system that allows us to see daylight modeling. If it’s a larger metal building, we can do basic modeling to show the architects how much light a design could bring in,” Mitchell says.

While new materials such as polycarbonates and PVCs have been introduced, makers of fiberglass panels have not been standing still. Major Industries’ fiberglass skylight option, Guardian 275, has been improved significantly since it was first offered in the 1980s.

“The main performance advancements have been in the fiberglass reinforced polymer face sheets,” Mitchell relates. “The technology has increased durability and enables us to offer longer warranties.” Since 2006, he adds, “We’ve eliminated the worry of color shifting because it’s now covered until the complete system needs to be replaced.”

According to Mitchell, fiberglass skylights can last up to 30 years — twice the life expectancy for polycarbonate multiwall panels. “And glass skylights are the longest-lasting material,” he adds.
“In 20 to 25 years, the glazing and sealants will start to break down. But if repaired at that time, glass skylights could last up to 50 years.”

Whatever skylight material a metal builder may favor, Mitchell offers a final word of advice.

“Make sure,” he says, “that your supplier has the ability to offer a wide range of daylighting options.”

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