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| > | Air Handling |
Air Handing Applications
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Insulation And Air Duct Systems
One of the most important systems in any building is the HVAC system. One component of the HVAC system is the air handling duct system. Fiber glass insulation products are used in the majority of duct systems installed in the United States, and serve as key components of a well-designed, operated and maintained HVAC system that will provide both thermal and acoustical benefits for the life of the building.
Types Of Fiber Glass Insulated Air Duct Products
There are four types of fiber glass insulated air duct products on the market today:
Fiber Glass Duct Liner
Fiber glass duct liners are blankets or boards of glass fiber insulation with either a coating or a fibrous mat on the surface facing the airstream. They are used as a thermal and acoustical insulation and are applied to the inside of sheet metal ductwork with metal fasteners and adhesives. They are available in a variety of densities and thicknesses.
Fiber Glass Duct Board
Fiber glass ducts are fabricated from 1", 1-
1/2" or 2" thick rigid boards of insulation manufactured from resin bonded inorganic glass fibers. This bonding keeps the fibers in place throughout the life of the installation. It is widely used in residential and light commercial HVAC systems operating at +2" wg static pressure, up to 2,400 fpm internal velocity. The outside surface of the board is a factory applied reinforced aluminum/kraft laminate that serves as the air barrier and water vapor retarder. Fiber glass duct board systems control heat loss or gain through the duct wall, help to control moisture condensation and are substantially air-tight when properly fabricated and sealed. These systems are fabricated either in the contractor’s shop or at the job site. They provide acoustical and thermal benefits plus certain economic and engineering advantages in some applications. R.S. Means Mechanical Cost Data conducted a cost comparison on ductwork products which showed the cost savings of fiber glass duct board over other solutions. Click here to see the data.
Fiber Glass Duct Wrap
Duct wrap is a flexible, resilient blanket, which is applied to the exterior of sheet metal ducts. It can be easily cut and fitted to achieve a neat, thermally effective exterior insulation blanket over rectangular, round, oval or irregularly shaped duct surfaces. Duct wrap is factory-laminated to a vapor retarder facing and is available in various thicknesses and densities. When applied to the exterior of metal ducts, this product controls condensation and reduces heat loss or gain.
Fiber Glass Commercial Board
Fiber Glass Commercial boards are manufactured in various stiffnesses, from flexible to rigid. The are available unfaced, or with FSK or ASJ Facings. They are applied to round, rectangular, oval or irregular shaped ducts, plenums, chillers and other equipment and are used to reduce heat loss or gain through duct, plenum or equipment walls.
Benefits Of Fiber Glass Air Duct Insulation Products In An HVAC System
As key components of a well-designed, operated and maintained HVAC system, fiber glass air handling insulation products improve the overall quality of the indoor environment. These materials not only provide cost-effective delivery of indoor environmental quality, they conserve energy, maintain air temperature, and control noise and condensation.
Energy Conservation
The insulating role of fiber glass duct board, duct wrap and duct liner has become even more important with the increased emphasis on ventilation. Increased ventilation requirements place more demands on a building’s energy source. The importance of energy efficiency is increasing in terms of overall energy conservation and the affordability of increased ventilation.
Consistent Air Temperature
By reducing the heat transfer across the duct system, fiber glass insulation products allow a building’s HVAC system to deliver conditioned air at design temperatures. Consistent air temperatures mean increased comfort for building occupants without over-taxing the energy source, while maintaining lower energy costs.
Noise Control
Without fiber glass insulation products, the acoustical environment of mechanically conditioned buildings can be greatly compromised. Fiber glass duct board and duct liner reduce the transmission of HVAC noise through the duct system, such as expansion and contraction of steel ducts (popping and cracking), air turbulence, etc. Fiber glass acoustical insulation also reduces noise transfer (cross-talk) from one room to another through the ducts. Click here for literature on noise control.
Condensation Control
Fiber glass duct liner, wrap and board help control condensation in air conditioning duct systems, reducing the opportunity for microbial growth. Condensation will form on bare sheet metal air-conditioning ducts at any point at which the duct surface temperature reaches the dewpoint. The moisture may remain in place or drip, causing moisture damage and creating a potential for microbial contamination. Fiber glass insulation corrects this problem by reducing moisture occurrence, thus eliminating a precondition for microbial growth. Click here for more on duct insulation and moisture.
Fiber Glass Air Handling Systems And The Indoor Environment
Our health is affected by the air we breathe. In recent years, as Americans have become more health conscious, increased attention has been focused on the quality of air in the indoor environment. The National Institute for Occupational Safety and Health (NIOSH) has identified inadequate ventilation as a major source of poor indoor environmental quality (IEQ). As a result, whenever IEQ problems arise, the focus of attention is often on the HVAC system, and because fiber glass insulation is found in many air handling systems today, it is often targeted when IEQ complaints arise.
In reality, fiber glass insulated duct products can serve as part of the solution to poor IEQ. As long as fiber glass air handling products are installed and maintained according to specifications, they can, in fact, improve the overall quality of the indoor environment. Studies show that when fiber glass insulation materials are properly installed, operated, and maintained, they do not support growth of microbials, in accordance with ASTM standards.
A regular schedule of preventive maintenance is all it takes to keep an HVAC system clean and operating at peak efficiency, whether the system uses bare sheet metal or has internally insulated ducts.
To ensure that an HVAC system is operating properly, remember the following:
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Any accumulation of dirt and debris in the ducts can be mechanically cleaned. |
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Make sure to select the correct high efficiency filtration equipment and replace it regularly. |
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Make sure the inspection program includes detection and remediation of probable sources of airborne contaminants and moisture. |
Click here for additional information on duct cleaning and air handling system maintenance issues.
Results Of Scientific Research On Fiber Glass Insulated Air Duct Systems
The results of recent scientific studies demonstrate that fiber glass insulated HVAC systems have no adverse effects on indoor environmental quality. Studies were conducted by Duke University and the University of Nevada Las Vegas. The findings from this research are summarized below.
Duke University
A 1997 study by Duke University showed that mold is no more likely to grow on fiber glass than on any other surface in the duct system. The true culprit in mold growth is the presence of water. By helping to reduce condensation, fiber glass insulated ducts actually help minimize microbial growth.
University of Nevada Las Vegas
A 1996 study by the University of Nevada Las Vegas confirms the results of numerous earlier studies which showed that fiber content in the indoor air from fiber glass lined systems is insignificant and does not adversely affect the health of building occupants. A second study by UNLV shows that mold grows at the same rate on lined sheet metal, duct board or bare metal.
Duct Board Fabrication And Installation – An Industry Training Program
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While specifiers, owners and building code officials generally accept fiber glass duct products as a good performance alternative to traditional sheet metal ducts, the variable, in their mind, is often the quality of the fabrication and installation of the products.
HVAC instructors need to have the right information to make sure their technicians are properly prepared for today’s competitive job market. To meet this need, NAIMA has taken the initiative to expand its training efforts by sponsoring "Train-the-Trainer" workshops around the country. NAIMA’s Fiber Glass Duct Board Training Program is designed for individuals responsible for training HVAC mechanics and technicians.
Click here to learn more about the Duct Board Train-the-Trainer program.
Related Literature
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Publication Title
(Click for full description, related publications and order form for printed versions) |
Pub No.
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Free Download
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| A Guide to Insulated Air Duct Systems | AH121 |  PDF 1.7 MB |
| Facts #64: Fibrous Glass Duct Systems | AH137 | PDF 219 KB |
| Facts #65: Fibrous Glass Duct Liner | AH138 | PDF 227 KB |
| Facts #66: Fibrous Glass Duct Wrap | AH139 | PDF 220 KB |
| Facts #67: Fibrous Glass Commercial Insulation Boards | AH140 | PDF 190 KB |
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Visit the Air Handling section of the Literature Library for a complete listing of publications on insulated air duct systems.