Duct insulation codes are primarily focused on energy efficiency, but the thermal, acoustic and weight properties of insulation can also influence insulation selection.
David Burd, air distribution products technical manager for North America at Owens Corning, said there’s a whole host of options to consider when determining what insulation to use in a project. However, the most available and common insulation products for HVAC duct insulation are elastomeric foam and fiberglass-based.
Both products are instrumental for improving energy efficiency across the world, but they differ from each other in cost, weight, acoustic and thermal properties, which building codes generally leave to manufacturers and industry associations to delineate for the market.
“Codes don't take into account what is needed in a specific region for condensation control, noise control, and those types of things. Now, don't get me wrong, it is written in code language for certain building types, where they need to meet certain acoustic parameters for example,” Burd said.
He cautions that building codes set a minimum standard, and in the case of acoustics, this standard relies on sound adsorption and the noise reduction coefficient. But there are other more granular measures for acoustics as well.
“Owens Corning feels that it's important to be able to provide the industry and our customers with the best possible information to make an educated decision on what product – thickness and so forth – is going to best serve the needs and the goals that you're trying to meet in this building,” Burd added.
With that goal in mind, he said the sound absorption ratings of elastomeric and fiberglass insulations are essentially the same, but a metric called insertion loss, otherwise known as ASTME 477, shows the differences between the two on frequency by frequency basis.
“Instead of giving you this average number, that's representative of the whole, what insertion loss does is give you the individual data per frequency band, and it'll tell you what the decibel loss is per foot of material,” Burd said.
For locales like health care facilities, this can be important.
“When you're looking at specific frequency ranges, say for example, 50 to 250 hertz, for system noise, like fan noise, startup air handling unit noise, that type of thing. There within insertion loss, you begin to see some differentiating performance factors, where fiberglass is outperforming elastomeric duct liner, simply by the nature of the product,” Burd said. “And that's true as well when you're looking at 250 to 1000 hertz, when you start getting into the speech range.”
He notes fiberglass insulation also weighs less, resulting in lower cost.
“You’re essentially getting better performance acoustically, same or better performance thermally, with a lighter product,” Burd concluded.
To learn more from Burd, listen to his full podcast interview with SNIPS NEWS below.