As mechanical and energy code requirements multiply, and as building owners demand more comfort and energy efficiency, the long-standing dominance of sheet metal air distribution technology is giving way to a superior solution.
Fiber glass duct insulation has become the choice of professionals for heating, ventilating, and air-conditioning systems in industrial, commercial, and institutional buildings. The reasons are a matter of economics and comfort, since fiber glass duct insulation reduces energy usage, increases the system’s effectiveness, and greatly improves a building’s acoustical environment.
When properly specified and correctly installed, fiber glass air handling insulations and ductboard products significantly contribute to complying with indoor environmental quality (IEQ) requirements, including energy performance. They deliver conditioned air closer to the design temperature, eliminating the need to extend heating or cooling cycles, and reducing fan requirements – thereby reducing energy costs.
New standards enacted this summer for state-owned buildings under the federal Energy Policy Act (EPAct) increase energy-efficiency requirements by about 6 percent over the previous standard, while applying the new standards in alterations and renovations increases total energy savings by as much as 50 percent. Fiber glass duct insulation has extremely low air leakage and is an excellent tool for complying with the new standards and reducing energy consumption.
A bare sheet metal duct carrying 55-degrees-F.-cooled air through an 80-degrees-F. plenum space can gain almost 10 degrees F. for every 100 feet it travels. In contrast, air carried the same distance through a duct lined or fabricated with just 1 inch of fiber glass insulation gains less than 2 degrees F.
Fiber glass duct insulation controls and reduces noise. Traditional sheet metal air ducts can transmit and even amplify sounds from the air handler or from occupants in other parts of the building. Fiber glass, however, dampens and absorbs sounds so that the indoor environment is easy on the ears. According to the Noise and Vibration Committee of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE): “Fiber glass duct systems insulation continues to be the most cost-effective solution to noise control in most HVAC air duct systems.”
Making the Right Choice
There are three broad categories of duct insulations available, providing a range of benefits. External insulations, including flexible duct wrap or rigid board insulation, are applied to the outside of the duct and serve as vapor retarders and thermal insulators. While they offer some improvement in efficiency, they have no impact on acoustical performance. Fiber glass duct liners are applied to the interior of duct surfaces during the duct fabrication process and provide excellent noise absorption characteristics and high thermal (R-value) performance.
Fiber glass duct board is made of rigid, high-density fiber glass with a tough aluminum exterior that combines thermal and acoustical insulation in a structural board package, completely eliminating the need for expensive sheet metal duct. Fiber glass duct board is taking over as the choice for builders who face the volatile cost of sheet metal. Installers prefer fiber glass duct board because it may be fabricated more quickly on-site. And, because duct board is readily available at stable prices, building owners can predict and control construction costs.
Eric G. Schakel is market manager, air handling insulations, for Johns Manville (www.jm.com), based in Denver.