A GUIDE TO
INSULATED
HVAC DUCT
SYSTEMS
• EFFICIENT AIR DELIVERY
• OCCUPANT COMFORT
• IMPROVED AIR QUALITY
• QUIET, COST EFFECTIVE
• ENERGY CONSERVATION
COPYRIGHT © 2003, NAIMA, ALL RIGHTS RESERVED
,Contents
Introduction ................................................................................................................................................................................1
General descriptions of types of insulated duct systems ....................................................................................................2-5
How fibrous glass duct insulation improves the indoor environment ......................................................................................6
Codes and Standards ..........................................................................................................................................................7-17
Fibrous glass duct systems ................................................................................................................................................18-21
Sheet metal ducts with fibrous glass insulation liner ........................................................................................................22-25
Sheet metal ducts with fibrous glass insulation wrap........................................................................................................26-29
Fibrous glass insulation boards..........................................................................................................................................30-33
Flexible duct systems..........................................................................................................................................................34-36
Insulating return air systems, ducted and non-ducted ..........................................................................................................37
Guide Specifications: 3-Part Masterformat®
Fibrous Glass Duct Work - Thermal/Acoustical Insulation ........................................................................................38-40
Sheet Metal Ducts - Acoustical Lining Insulation ......................................................................................................40-42
Sheet Metal Ducts - Thermal Insulation Wrap ............................................................................................................42,43
Facts on fibrous glass duct insulation................................................................................................................................44,45
,FIBROUS GLASS INSULATED HVAC DUCT SYSTEMS
FIBROUS GLASS INSULATED HVAC DUCT SYSTEMS
and how they provide ...
• Quiet, efficient air delivery
• Improved indoor environmental quality
• Cost-effective energy conservation
• Enhanced occupant comfort
Introduction Types of insulated air duct systems
Fibrous glass has been used as thermal and acoustical The five types of insulated air duct systems described
insulation in forced air heating, ventilating, and air- in this guide can be used to meet all widely used
conditioning systems ever since these systems became architects’ or engineers’ specifications, local codes,
widely available following World War II. Today, fibrous owners’ comfort control requirements, installed and
glass duct systems, duct liners, duct wraps, and life cycle cost criteria, or the contractor’s crew skill
commercial insulation boards contribute to indoor levels and shop fabrication resources.
environmental quality (IEQ) and occupant comfort in
residential, commercial, industrial, and public buildings of Combining types of fibrous glass insulation in duct
all kinds. These include homes, apartments, schools, systems
hotels, motels, medical facilities, theaters, shopping Often more than one of type of fibrous glass insulation
centers, office and government buildings, factories, and treatment may be specified in a single HVAC duct
many other types of structures where occupant comfort system. For example, in a variable air volume system,
and indoor environmental quality are important criteria. sheet metal ducts with fibrous glass duct liner may be
used on the high pressure side if design static pressure
Fibrous glass insulation is used in air duct systems for four exceeds the 2 in. w.g. (500 Pa) limits of the fibrous glass
basic reasons: duct system; the fibrous glass duct system may be used
on the low pressure side; and insulated flexible ducts
• Temperature control - Delivery of heated or cooled air at may be used as run-outs from trunk ducts to diffusers.
comfort levels suited to building occupancy requirements.
• Acoustical control - Absorption of noise generated by
central air handling equipment and movement of air
through the ducts, as well as “cross-talk” carried by ducts
from one space to another.
• Condensation control – Prevents condensation in or on
ducts when installed R-value recommendations are
followed, reducing the likelihood of moisture damage to
ceilings and other interior finishes.
• Energy conservation - Reduction of HVAC system
operating costs by controlling heat loss or gain through air
duct walls, helping systems run more efficiently.
HVAC systems typically operate with internal air
temperatures between 40˚F (4˚C) and 250˚F (121˚C).
Systems operating outside this range are not considered
in this guide, except that fibrous glass insulation boards
may be used in systems operating at internal air
temperatures between 0˚F (-18˚C) and 450˚F (232˚C).
1
, FIBROUS GLASS INSULATED HVAC DUCT SYSTEMS
GENERAL DESCRIPTIONS
Fibrous glass duct system
The fibrous glass duct system is used to conserve heating Duct board products are available with coated or faced
and cooling energy and to control duct-borne noise in airstream surfaces. These products permit rigorous
commercial, institutional, or residential heating, ventilating, cleaning of the duct surface where dust has been allowed
and air-conditioning ductwork operating in the range of + 2 to collect in the duct due to lack of filtration or poor
in. w.g. (+ 500 Pa) static pressure, up to at least 5,000 fpm maintenance. Additionally, some of these products have
(25.4 m/sec) internal air velocity, and internal air higher maximum velocity ratings.
temperature between 40˚F (4˚C) and 250˚F (121˚C). Ducts Duct systems fabricated from fibrous glass duct board
are only for indoor use and should be located in areas products qualify under UL 181 as Class 1 Air Ducts,
where ambient temperature does not exceed 150˚F (66˚C). meeting the fire safety requirements of NFPA 90A and 90B
The fibrous glass duct system is normally made up of including limited combustibility. They also comply with all
nominal four foot (1.2m) modules fabricated from 1, 11/2, widely used model codes. Duct board joint closures are
or 2 in. (25, 38, or 51mm) thick, flat fibrous glass duct sealed using one of three UL 181A listed systems.
board stock having a factory-applied reinforced aluminum
exterior air barrier finish. Duct system modules are
fabricated using either specially designed hand tools or
grooving and closure machines. Duct fittings such as tees,
offsets, elbows, and transitions are also fabricated from
these modules or from flat duct board stock.
UL 181A closure
systems provide
substantially air-tight
sealing
Reinforced aluminum
foil/kraft laminate,
air barrier, and vapor retarder
Factory-molded male and female shiplap
joints between sections
Thermally effective fibrous glass insulation
Internal surface treatments enhance cleanability
Fig. 1. Fibrous glass duct module
2
INSULATED
HVAC DUCT
SYSTEMS
• EFFICIENT AIR DELIVERY
• OCCUPANT COMFORT
• IMPROVED AIR QUALITY
• QUIET, COST EFFECTIVE
• ENERGY CONSERVATION
COPYRIGHT © 2003, NAIMA, ALL RIGHTS RESERVED
,Contents
Introduction ................................................................................................................................................................................1
General descriptions of types of insulated duct systems ....................................................................................................2-5
How fibrous glass duct insulation improves the indoor environment ......................................................................................6
Codes and Standards ..........................................................................................................................................................7-17
Fibrous glass duct systems ................................................................................................................................................18-21
Sheet metal ducts with fibrous glass insulation liner ........................................................................................................22-25
Sheet metal ducts with fibrous glass insulation wrap........................................................................................................26-29
Fibrous glass insulation boards..........................................................................................................................................30-33
Flexible duct systems..........................................................................................................................................................34-36
Insulating return air systems, ducted and non-ducted ..........................................................................................................37
Guide Specifications: 3-Part Masterformat®
Fibrous Glass Duct Work - Thermal/Acoustical Insulation ........................................................................................38-40
Sheet Metal Ducts - Acoustical Lining Insulation ......................................................................................................40-42
Sheet Metal Ducts - Thermal Insulation Wrap ............................................................................................................42,43
Facts on fibrous glass duct insulation................................................................................................................................44,45
,FIBROUS GLASS INSULATED HVAC DUCT SYSTEMS
FIBROUS GLASS INSULATED HVAC DUCT SYSTEMS
and how they provide ...
• Quiet, efficient air delivery
• Improved indoor environmental quality
• Cost-effective energy conservation
• Enhanced occupant comfort
Introduction Types of insulated air duct systems
Fibrous glass has been used as thermal and acoustical The five types of insulated air duct systems described
insulation in forced air heating, ventilating, and air- in this guide can be used to meet all widely used
conditioning systems ever since these systems became architects’ or engineers’ specifications, local codes,
widely available following World War II. Today, fibrous owners’ comfort control requirements, installed and
glass duct systems, duct liners, duct wraps, and life cycle cost criteria, or the contractor’s crew skill
commercial insulation boards contribute to indoor levels and shop fabrication resources.
environmental quality (IEQ) and occupant comfort in
residential, commercial, industrial, and public buildings of Combining types of fibrous glass insulation in duct
all kinds. These include homes, apartments, schools, systems
hotels, motels, medical facilities, theaters, shopping Often more than one of type of fibrous glass insulation
centers, office and government buildings, factories, and treatment may be specified in a single HVAC duct
many other types of structures where occupant comfort system. For example, in a variable air volume system,
and indoor environmental quality are important criteria. sheet metal ducts with fibrous glass duct liner may be
used on the high pressure side if design static pressure
Fibrous glass insulation is used in air duct systems for four exceeds the 2 in. w.g. (500 Pa) limits of the fibrous glass
basic reasons: duct system; the fibrous glass duct system may be used
on the low pressure side; and insulated flexible ducts
• Temperature control - Delivery of heated or cooled air at may be used as run-outs from trunk ducts to diffusers.
comfort levels suited to building occupancy requirements.
• Acoustical control - Absorption of noise generated by
central air handling equipment and movement of air
through the ducts, as well as “cross-talk” carried by ducts
from one space to another.
• Condensation control – Prevents condensation in or on
ducts when installed R-value recommendations are
followed, reducing the likelihood of moisture damage to
ceilings and other interior finishes.
• Energy conservation - Reduction of HVAC system
operating costs by controlling heat loss or gain through air
duct walls, helping systems run more efficiently.
HVAC systems typically operate with internal air
temperatures between 40˚F (4˚C) and 250˚F (121˚C).
Systems operating outside this range are not considered
in this guide, except that fibrous glass insulation boards
may be used in systems operating at internal air
temperatures between 0˚F (-18˚C) and 450˚F (232˚C).
1
, FIBROUS GLASS INSULATED HVAC DUCT SYSTEMS
GENERAL DESCRIPTIONS
Fibrous glass duct system
The fibrous glass duct system is used to conserve heating Duct board products are available with coated or faced
and cooling energy and to control duct-borne noise in airstream surfaces. These products permit rigorous
commercial, institutional, or residential heating, ventilating, cleaning of the duct surface where dust has been allowed
and air-conditioning ductwork operating in the range of + 2 to collect in the duct due to lack of filtration or poor
in. w.g. (+ 500 Pa) static pressure, up to at least 5,000 fpm maintenance. Additionally, some of these products have
(25.4 m/sec) internal air velocity, and internal air higher maximum velocity ratings.
temperature between 40˚F (4˚C) and 250˚F (121˚C). Ducts Duct systems fabricated from fibrous glass duct board
are only for indoor use and should be located in areas products qualify under UL 181 as Class 1 Air Ducts,
where ambient temperature does not exceed 150˚F (66˚C). meeting the fire safety requirements of NFPA 90A and 90B
The fibrous glass duct system is normally made up of including limited combustibility. They also comply with all
nominal four foot (1.2m) modules fabricated from 1, 11/2, widely used model codes. Duct board joint closures are
or 2 in. (25, 38, or 51mm) thick, flat fibrous glass duct sealed using one of three UL 181A listed systems.
board stock having a factory-applied reinforced aluminum
exterior air barrier finish. Duct system modules are
fabricated using either specially designed hand tools or
grooving and closure machines. Duct fittings such as tees,
offsets, elbows, and transitions are also fabricated from
these modules or from flat duct board stock.
UL 181A closure
systems provide
substantially air-tight
sealing
Reinforced aluminum
foil/kraft laminate,
air barrier, and vapor retarder
Factory-molded male and female shiplap
joints between sections
Thermally effective fibrous glass insulation
Internal surface treatments enhance cleanability
Fig. 1. Fibrous glass duct module
2
