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HVAC INSULATION- One of The Keys to a “HEALTHY BUILDING". Glenn Brower ASHRAE Technical Comm. Member Knauf Fiber Glass. Indoor Environmental Quality. LIGHTING QUALITY. AESTHETICS. AIR PURITY. ACOUSTICAL COMFORT. THERMAL COMFORT. THE ROLE OF HVAC INSULATION IN IEQ.

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Hvac insulation one of the keys to a healthy building l.jpg

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

Glenn Brower

ASHRAE Technical Comm. Member

Knauf Fiber Glass


Indoor environmental quality l.jpg
Indoor Environmental Quality

LIGHTING

QUALITY

AESTHETICS

AIR PURITY

ACOUSTICAL

COMFORT

THERMAL COMFORT


The role of hvac insulation in ieq l.jpg
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


Thermal comfort l.jpg
THERMAL COMFORT

AIR TEMPERATURE

AIR QUANTITY & VELOCITY


Thermal performance of duct insulations l.jpg
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 T’s 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 ROUGHNESS

Duct Breakout & Breakin

Duct Attenuation Loss

Duct Rumble


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Air Ducts Are “Speaking Tubes” ROUGHNESS

  • 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 ROUGHNESS

  • 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 ROUGHNESS

  • 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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IF ATTENUATION IS THE GOAL, HOW DO YOU SPECIFY WHAT YOU WANT?

  • Unless all duct sizes are the same, don’t specify internal liner by dB/meter or dB’s 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 WANT?

  • 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? WANT?

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 WANT?

  • 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 WANT?

  • 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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AIR PURITY WANT?

PARTICULATE MATTER

VOC EMISSIONS

BIOLOGICAL CONTAMINANTS


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PARTICULATE MATTER - THE ROLE OF INSULATIONS WANT?

  • 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 WANT?

  • 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


1994 building construction industry advisory committee study l.jpg
1994 BUILDING CONSTRUCTION INDUSTRY ADVISORY COMMITTEE STUDY WANT?

  • 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 WANT?

  • 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


Hvac insulations and biological contaminants l.jpg
HVAC INSULATIONS AND BIOLOGICAL CONTAMINANTS WANT?

  • 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 WANT?

  • Moisture is the essential element required for fungal growth

  • Studies in static environmental chambers have shown that fungal growth will initiate at RH>=65%

  • Field studies in buildings where RH is regularly >65% show that fungal growth is rare


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DUKE UNIVERSITY STUDY WANT?

  • 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 WANT?

  • 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


Biocides and encapsulants cont l.jpg
BIOCIDES AND ENCAPSULANTS (CONT.) WANT?

  • 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 mfr’s warranty

  • These treatments are not recommended for FG except for very limited spot repairs


Volatile organic chemical emissions l.jpg
VOLATILE ORGANIC CHEMICAL EMISSIONS WANT?

  • VOC’s 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




The practicality of zero voc emission materials l.jpg
THE PRACTICALITY OF ZERO VOC EMISSION MATERIALS WANT?

  • Many materials in the interior spaces of buildings emit VOC’s

  • 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? WANT?

  • 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


Summary l.jpg
SUMMARY WANT?

  • 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


Reference resources on all aspects of insulation and ieq l.jpg
REFERENCE RESOURCES ON ALL ASPECTS OF INSULATION AND IEQ WANT?

  • NORTH AMERICAN INSULATION MFR’S ASSOCIATION

    • www.naima.org

  • Knauf Fiber Glass - www.knauffiberglass.com

  • ASHRAE Handbooks


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