Knauf Duct Wrap with PSK facing was selected instead of a more conventional silver foil-faced product.
SOUTH BEND, Ind. - General Motors' new Hummer H2 sport utility vehicle is going to be noticed on the roads this spring. It's a vehicle that's hard to miss. It's described as a less expensive and more refined version of the tanklike Hummer H1 seen on so many movie screens and war zones near you.

The Hummer H2, inaccurately dubbed "baby Hummer" by the media (actually it's almost as big as the original) will come from a General Motors plant near South Bend.

At $50,000 or so, each H2 comes loaded with amenities and creature comforts. It's not like the spartan interior of the original AM General Hummer. Because of that, GM expects to sell 35,000 to 40,000 in its first year of production, versus 1,000 for the original Hummer, which is still being built by AM General.

Aside from the vehicle, even the plant is a bit unusual. "For the person who works here everyday, it's important for the plant to look nice," said Rick Bernard, mechanical/electrical coordinator for architect Albert Kahn Associates. "If the workers aren't happy with their environment, then the product that goes out the back door is going to reflect that."

That idea applied to duct insulation as well. Knauf Duct Wrap with PSK facing was selected instead of a more conventional silver foil-faced product. The insulation's white PSK facing is a tri-laminate material composed of a white metalized polypropylene film, a fiber glass reinforcing scrim and white kraft. PSK combines a bright finish with improved resistance to punctures, tears and moisture.

"It looks clean and bright," said Bernard. "We don't have to paint it to get a nice, shiny finished look. That saves our contractors time, and you can see the difference it makes in the atmosphere it projects throughout the plant."

Dual service supply ducts

Of course, performance is more important than aesthetics. About 120,000 sq. ft. of Knauf Duct Wrap was used on dual service supply ducts in the plant's hvac system, which includes in-line gas burners for heating and three screw-type chillers that supply 448F chilled water for cooling. Seventeen air handling units with an average capacity of 60,000 cfm each distribute conditioned air.

The insulation contractor, Gribbins Insulation, Evansville, finished the Hummer plant in four months, with just four crew members on-site.

One important challenge for the insulation was preventing condensation on ducts during cooling operation (558F supply air temperature), a daunting task given the use of 100% fresh air during those humid Indiana summers. One of the advantages that Knauf's PSK facing provided over traditional white vinyl was a significantly lower moisture vapor transmission rating (.02 perms - ASTM E 96, Procedure A) to help prevent water vapor from migrating toward the cold ducts.

The insulation also had to resist the normal abuse and wear of the job site. The PSK facing offers a puncture resistance rating of 25 (TAPPI Test T803, Beach Units).

Brian Willet, project manager for Gribbins Insulation, said "Our installers like it, and it solved a design challenge for the engineers. So it turned out to be a good solution all around."

The steel fabricator on the job was Art Iron (local subsidiary - St. Joe Valley); the steel erector was Cisco.