Duct Sealing

Duct Sealing Benefits

Properly sealing ductwork results in several benefits. It improves comfort by increasing the rate at which air is delivered to a space; it can prevent safety problems caused by carbon monoxide gas leaking from water and space heating equipment; and it improves indoor air quality by reducing the infiltration of dust, humidity, and outdoor fumes and odors. It also saves energy. The most cost-effective time to have duct sealing performed is when an HVAC system is first installed in new construction, because the ducts are easily accessed. However, ductwork can also be sealed in existing buildings.

Duct sealing may be justified on the basis of its non-energy benefits; however its cost-effectiveness based on energy savings alone is unclear. Research from Lawrence Berkeley National Laboratory shows that 10 to 20 percent of the air from an HVAC supply fan is wasted through leaks in commercial buildings. Stopping this leakage could create significant dollar savings in certain climates. However, the cost of sealing ducts in commercial buildings, particularly in existing ones, is not well established and depends on many factors.

Tapes and mastic.
Metal-reinforced tapes and mastic approved by Underwriters Laboratories are the preferred, conventional choice for duct sealing. Mastic is rubbery, fiber-reinforced substance that is applied with a brush. Large holes are generally patched with sheet metal and then sealed with mastic. Duct sealing is still often performed with standard duct tape; despite its name, duct tape is a poor material for that purpose.

Aerosol sealants.
A technology sold under the trade name Aeroseal by the Carrier Corporation has the potential to dramatically mitigate leaks and the problems they cause. It works by blowing sticky particles into ducts. The particles attach themselves to the edges of leaks and effectively seal them. Sold as part of a franchised service that includes diagnostics, repair, safety testing, sealing, and reporting, Aeroseal is the only technology on the market that can seal leaks in ducts made inaccessible by walls and insulation.

Consider the overall duct sealing package.
Aeroseal franchises compete with other duct sealing and diagnosing contractors, whose services vary widely in sophistication and effectiveness. These competitors offer less-expensive (but also less-effective) sealing treatments. Anyone considering the use of Aeroseal should weigh its additional benefits over conventional sealing techniques. These benefits include the ability to seal leaks that can’t otherwise be reached, safety testing, and the production of detailed performance reports.

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