HVAC INSULATION- One of The Keys to a

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HVAC INSULATION- One of The Keys to a HEALTHY
BUILDING"

• Glenn Brower
• ASHRAE Technical Comm. Member
• Knauf Fiber Glass

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Indoor Environmental Quality
LIGHTING QUALITY
AESTHETICS
AIR PURITY
ACOUSTICAL COMFORT
THERMAL COMFORT
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THE ROLE OF HVAC INSULATION IN IEQ

• Thermal - helps to deliver air at the design
  temperature, save energy and minimize
  condensation
• Acoustical - helps to reduce sound down the
  ducts, breakout noise, crosstalk
• ventilation - can insulate without contributing
  to indoor pollution
• aesthetics - depending on application, can be
  finished to blend in

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THERMAL COMFORT
AIR TEMPERATURE
AIR QUANTITY VELOCITY
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THERMAL PERFORMANCE OF DUCT INSULATIONS

• Both internal and external insulations can
  deliver required R-values
• R-values should be specified based on installed
  thickness
• Duct Wraps are installed with 25 compression
• Most codes specify R-values based on ASTM C518 or
  C177 testing
• no air film benefits are allowed
• Radiant barrier insulations tested at high delta
  Ts will not deliver R-value in duct applications

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DUCT THERMAL PERFORMANCE

• Temperature Drop or Gain can drive insulation
  above code requirements
• example, 305mm x 610mm duct, delivering air at
  12.50 C, at a velocity of 305 meters/min over a
  length of 30 meters in a space at a temperature
  of 270 C, would have the following temperature
  gains
• uninsulated, 40 C
• insulated to R-0.74 m2-C/W, 0.80 C

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DUCT THERMAL PERFORMANCE

• Condensation Control - eliminating sweating as a
  contributor to mold growth

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AIR FLOW CONSIDERATIONS WITH INTERNAL LINED
SYSTEMS

• The use of any type of material on the inside of
  a sheet metal duct will have some type of
  associated friction loss
• friction loss can be calculated from surface
  absolute roughness factors
• galvanized steel, 1.22 m joints 0.091 mm
• galvanized steel, 0.61 m joints 0.152 mm
• fg liner with mat-faced airstream 0.914 mm
• fg liner with coated airstream 3.048
  mm

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COMPARISON OF FRICTION FACTORS FOR DIFFERENT
ABSOLUTE ROUGHNESS
COATED MAT OR FLEX DUCT
LINER W/ MAT
BARE METAL
Pressure loss is linear with friction
factor Pressure loss is linear with Hydraulic
Diameter 4A/P Pressure loss is the square of
velocity, a factor of 2 in f 30 velocity loss
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ACOUSTICAL COMFORT
Duct Breakout Breakin
Duct Attenuation Loss
Duct Rumble
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Air Ducts Are Speaking Tubes

• Direct energy through a very focused area.
• Carry equipment noise, damper noise, and other
  duct noise.
• Can generate their own noise through expansion,
  contraction, or air velocity.
• Carry office noise from interconnected spaces.

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ACOUSTICAL PERFORMANCE OF HVAC INSULATION

• Attenuation measure of sound dissipation as it
  travels down the duct. Typically measured as
  insertion loss - ASTM E477

STANDARD DUCT SECTION - NO TREATMENT
TEST DUCT SECTION - ACOUSTICAL TREATMENT
The difference is insertion loss, dB per linear
dimension
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THE ABILITY OF DUCT LINER TO PROVIDE ATTENUATION

• ASHRAE Applications, Sound and Vibration Control
  gives data on effectiveness of duct liner over a
  large range of rectangular duct sizes
• insulation thickness is the primary driver for
  attenuation
• product density is an insignificant factor
• as duct size increases, effectiveness of internal
  lining is diminished

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COMPARISON OF ASHRAE ATTENUATION DATA FOR
RECTANGULAR DUCTS
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ASHRAE ATTENUATION DATA FOR RECTANGULAR ELBOWS
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COMPARISON OF ASHRAE ATTENUATION DATA FOR ROUND
DUCTS
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ASHRAE ATTENUATION DATA FOR ROUND ELBOWS
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IF ATTENUATION IS THE GOAL, HOW DO YOU SPECIFY
WHAT YOU WANT?

• Unless all duct sizes are the same, dont specify
  internal liner by dB/meter or dBs at the target
• changes for every duct dimension change
• does the contractor include ells and other
  fittings?
• Specify internal liner by sound absorption
• gives an easy way to compare materials

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SOUND ABSORPTION TESTING

• Uses the Reverberation Room (ASTM C423) method,
  which measures ability to absorb random incidence
  sound
• 6.69 square meters of test material in the room
• The mounting method plays a large part in the
  values obtained
• for repeatability, duct liners should be tested
  using the Type A mounting
• Test yields absorption values for each freq.
  band, also calculates an average, NRC

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HOW CAN SOUND ABSORPTION CAN BE RELATED TO DUCT
ATTENUATION?
Relationship between absorption attenuation is
nearly linear 10
Relationship between absorption attenuation is
nearly linear 7.5
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DUCT RUMBLE, BREAKOUT BREAKIN NOISE

• Thermal insulations do not have enough mass to be
  effective over most frequencies
• Flexible insulations in combination with mass can
  be helpful
• for round ducts, can be directly attached, for
  rectangular, both the insulation and the mass
  should be physically separated from the duct

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NOISE CONTROL FOR EQUIPMENT AND PIPING

• Rigid insulation materials tend to pass the
  majority of vibrating energy right through with
  minimal attenuation.
• Fibrous insulation is a much better attenuator.
  In specific applications one may have to install
  fibrous insulation over rigid insulation.
• For extra attenuation, use multi-layered fibrous
  insulation with hard septums between layers.

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THE DILEMNA OF REDUCING NOISE FROM MULTIPLE
SOURCES
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AIR PURITY
PARTICULATE MATTER
VOC EMISSIONS
BIOLOGICAL CONTAMINANTS
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PARTICULATE MATTER - THE ROLE OF INSULATIONS

• External duct insulations should not contribute
  to dust levels in the occupied space
• Internal duct insulations are designed to be
  non-contributors when properly installed
• FG duct liners are tested at 2.5 times rated
  velocity, including an elbow without vanes, to
  assure that they can withstand air velocity abuse
• numerous studies have shown fiber levels to be at
  background levels

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TOUGHNESS OF INTERNAL INSULATIONS

• The Surfaces of FG Liners will also take normal
  abuse from cleaning procedures
• soft brushes or air washes will not damage the
  airstream surface
• cutting into the duct should be done carefully so
  as not to damage the insulation
• closing the duct after cleaning is also critical
  for future integrity

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1994 BUILDING CONSTRUCTION INDUSTRY ADVISORY
COMMITTEE STUDY

• Evaluated duct cleaning methods for effectiveness
  in cleaning the duct surface and improving indoor
  air quality
• contact method (conventional vacuum cleaning)
• air sweep method (compressed air through a
  nozzle)
• mechanical brush method (rotary brush in
  combination with vacuum collection)

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BCIAC STUDY RESULTS

• Studied 8 identical homes in a single
  neighborhood, 2 homes for each method and 2
  controls
• Results
• particle count readings were higher during
  cleaning than before or after cleaning
• cleaning did not lead to higher indoor fiber
  counts
• air sweep method showed the greatest reduction in
  bioaerosol concentration, although none caused
  significant improvement

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HVAC INSULATIONS AND BIOLOGICAL CONTAMINANTS

• FUNGAL GROWTH
• requires both moisture and nutrients
• dirt and fungal spores are present almost
  everywhere, therefore they will inevitably be
  deposited on duct surfaces
• this is true regardless of the nature of the duct
  surface
• the only way to minimize this deposition is
  through the use of better filtration

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THE ROLE OF WATER AND FUNGAL GROWTH IN HVAC
SYSTEMS

• Moisture is the essential element required for
  fungal growth
• Studies in static environmental chambers have
  shown that fungal growth will initiate at RHgt65
• Field studies in buildings where RH is regularly
  gt65 show that fungal growth is rare

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DUKE UNIVERSITY STUDY

• Duke University - extensively studied 6 buildings
  in the Piedmont region
• Heavy deposition of dirt and fungal spores on all
  surfaces inspected
• no fungal growth on fresh air intakes, hot deck
  surfaces or hot deck air distribution surfaces
• no evidence of fungal growth on the cold deck of
  dual-deck systems wherever intake air was
  preconditioned
• it is the condensation of water on surfaces at
  dew point that have fungal growth

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USE OF BIOCIDES AND ENCAPSULANTS WITH INTERNAL
INSULATIONS

• All FG internal insulations are already treated
  to be fungal and bacterial inhibited
• when dry, these products will not sustain fungal
  growth
• It is very difficult to get significant coverage
  of the air stream surface except where it is
  directly applied and visually confirmed
• small areas of repair that can be directly
  reached may be effectively coated

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BIOCIDES AND ENCAPSULANTS (CONT.)

• Application of these materials could have human
  health consequences
• Fire safety consequences - none have been tested
  in combination with the insulation, and quantity
  will be difficult to control
• Long term effects - may degrade integrity of air
  stream surface, definitely voids mfrs warranty
• These treatments are not recommended for FG
  except for very limited spot repairs

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VOLATILE ORGANIC CHEMICAL EMISSIONS

• VOCs are increasingly recognized as significant
  contributors to poor indoor air quality
• Insulation materials, including duct insulations,
  have long been tested for VOC emissions and shown
  to be very low contributors
• meet US EPA indoor emission requirements, State
  of Washington, State of Alaska, and State of
  California requirements

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COMPARISON OF VOC EMITTERS
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DECAY OF EMISSIONS FROM FIBER GLASS
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THE PRACTICALITY OF ZERO VOC EMISSION MATERIALS

• Many materials in the interior spaces of
  buildings emit VOCs
• Each VOC has a normal partial pressure that is a
  function of RH and temperature
• if there are multiple sources of a VOC each will
  contribute until the partial pressure is reached
• some materials that contain a VOC may actually
  act as a sink in the presence of stronger sources
• Zero emitting materials in the presence of high
  emitters makes no sense

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HOW CAN A SPECIFIER ADDRESS LOW VOC EMISSIONS?

• Follow the guidelines of the US Green Building
  Council
• the LEED design system addresses low emitting
  sources
• There is a independent, recognized certification
  body that addresses all type of building
  materials and furnishings
• Greenguard is very much like Underwriters
  Laboratories
• Greenguard is recognized by LEEDS for maximum
  points

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SUMMARY

• Thermal benefits
• radiant effects are not applicable for most ducts
• Acoustical benefits
• tradeoffs to cellular non-fibrous materials carry
  a severe acoustical penalty
• Minimal air quality issues in well designed
  systems
• water is the issue, design to prevent it
• filtration selection maintenance will minimize
  any need for cleaning

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REFERENCE RESOURCES ON ALL ASPECTS OF INSULATION
AND IEQ

• NORTH AMERICAN INSULATION MFRS ASSOCIATION
• www.naima.org
• Knauf Fiber Glass - www.knauffiberglass.com
• brad.omlid_at_knauffiberglass.com,
• glenn.brower_at_knauffiberglass.com, 317-398-4434,
  x8801
• ASHRAE Handbooks