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

Glenn Brower

ASHRAE Technical Comm. Member

Knauf Fiber Glass

Indoor Environmental Quality

AIR PURITY THERMAL

COMFORT

ACOUSTICAL COMFORT

LIGHTING

QUALITYAESTHETICS

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

AIR TEMPERATURE

AIR QUANTITY &

VELOCITY

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

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

DUCT THERMAL PERFORMANCE

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

REQUIRED R-VALUE FOR 0.1 EMISS

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

20 25 30 35 40

AMBIENT TEMPERATURE (C)

R-V

AL

UE

60% RH

70% RH

80% RH

90%RH REQ'D R-VALUE FOR 0.9 EMISS

0.00

0.50

1.00

1.50

2.00

2.50

21.1 26.7 32.2 37.8

AMBIENT TEMPERATURE

R-V

AL

UE

60% RH

70% RH

80% RH

90% RH

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 factorsgalvanized 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

COMPARISON OF FRICTION FACTORS FOR DIFFERENT ABSOLUTE ROUGHNESS

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

FRICTION FACTOR

0.01

0.015

0.02

0.025

0.03

0.035

0 0.5 1 1.5 2 2.5 3 3.5

Absolute Roughness (mm)

f (d

imen

sio

nle

ss)

305x610

610x610

610x1220

BARE METAL

LINER W/ MAT

COATED MAT OR FLEX DUCT

ACOUSTICAL COMFORT

Duct Attenuation

LossDuct Rumble

Duct Breakout &

Breakin

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.

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

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

COMPARISON OF ASHRAE ATTENUATION DATA FOR

RECTANGULAR DUCTS

DUCT LINERSIZE (mm)THICKNESS 125 Hz 250Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz

305x305 0 0.66 0.33 0.20 0.20 0.20 0.2025 1.31 2.62 6.23 13.12 13.45 9.1951 1.64 5.25 11.48 16.41 13.45 9.19

610x610 0 0.66 0.33 0.10 0.10 0.10 0.1025 0.66 1.64 4.59 9.19 7.22 5.9151 0.98 2.95 8.20 11.48 7.22 5.91

305x610 0 0.66 0.33 0.16 0.16 0.16 0.1625 0.98 1.97 5.58 11.48 10.50 7.5551 1.31 4.27 9.84 14.11 10.50 7.55

ATTENUATION LOSS dB/meter

ASHRAE ATTENUATION DATA FOR RECTANGULAR ELBOWS

RECTANGULAR ELLS - NO TURNING VANESDUCT LINER

WIDTH (mm) THICKNESS 125 Hz 250Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz

305 0 0.0 1.0 5.0 8.0 4.0 3.025 0.0 1.0 6.0 11.0 10.0 10.0

610 0 1.0 5.0 8.0 4.0 3.0 3.025 1.0 6.0 11.0 10.0 10.0 10.0

RECTANGULAR ELLS - WITH TURNING VANESDUCT LINER

WIDTH (mm) THICKNESS 125 Hz 250Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz

305 0 0.0 1.0 4.0 6.0 4.0 4.025 0.0 4.0 4.0 7.0 7.0 7.0

610 0 1.0 4.0 6.0 4.0 4.0 4.025 4.0 4.0 7.0 7.0 7.0 7.0

ATTENUATION LOSS dB

ATTENUATION LOSS dB

COMPARISON OF ASHRAE ATTENUATION DATA FOR ROUND

DUCTSDUCT LINER

SIZE (mm)THICKNESS 125 Hz 250Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz

152 0 0.10 0.16 0.16 0.33 0.33 0.3325 1.94 3.05 5.02 7.12 7.58 6.6951 2.62 4.49 7.38 7.12 7.58 6.69

305 0 0.10 0.10 0.16 0.23 0.23 0.2325 1.51 2.66 4.78 7.15 6.27 4.8651 2.20 4.10 7.15 7.15 6.27 4.86

610 0 0.07 0.07 0.10 0.16 0.16 0.1625 0.82 1.87 4.20 5.61 4.07 2.7951 1.51 3.31 6.56 5.61 4.07 2.79

ATTENUATION LOSS dB/meter

ASHRAE ATTENUATION DATA FOR ROUND ELBOWS

DUCTWIDTH (mm) 125 Hz 250Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz

152 0.0 0.0 1.0 2.0 3.0 3.0305 0.0 1.0 2.0 3.0 3.0 3.0610 1.0 2.0 3.0 3.0 3.0 3.00

ATTENUATION LOSS dB

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

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

HOW CAN SOUND ABSORPTION CAN BE RELATED TO DUCT

ATTENUATION?Sound Absorption vs Attenuation for 305x610mm

0

5

10

15

0 0.2 0.4 0.6 0.8 1 1.2

Absorption Value

Att

en

ua

tio

n (

dB

/m)

500 Hz

1000Hz

250 Hz

2000 Hz

Sound Absorption vs Attenuation for 610x610 mm

02468

101214

0 0.2 0.4 0.6 0.8 1 1.2

Absorption Value

Att

enu

atio

n (

dB

/m)

500 Hz

1000Hz

250 Hz

2000 Hz

Relationship between absorption & attenuation is nearly linear ~ 10

Relationship between absorption & attenuation is nearly linear ~ 7.5

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

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.

INSERTION LOSS (dB) INTO 6" IPS SCHEDULE 40 PIPE

TEST SPECIMEN 500 Hz 1000 Hz 2000 Hz 4000 Hz

4" MIN WOOL + 2 PSF ACOUSTI-JAC 12 21 34 37

4" FIBERGLASS + 2 PSF ACOUSTI-JAC 17 30 36 42

2" MIN WOOL + 2 PSF ACOUSTI-JAC 12 27 32 37

2" FIBERGLASS + 2 PSF ACOUSTI-JAC 16 25 33 40

4" MIN WOOL + 1 PSF ACOUSTI-JAC 15 28 35 44

4" FIBERGLASS + 1 PSF ACOUSTI-JAC 15 28 35 44

2" MIN WOOL + 1 PSF ACOUSTI-JAC 10 23 30 37

2" FIBERGLASS + 1 PSF ACOUSTI-JAC 13 20 32 40

Combining Decibel Levels

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 1 2 3 4 5 6 7 8 9 10 11 12 13

dB Difference Between Two Sources

dB

To

Ad

d T

o L

arg

er

Le

ve

l

THE DILEMNA OF REDUCING NOISE FROM MULTIPLE SOURCES

AIR PURITY

PARTICULATE MATTER BIOLOGICAL

CONTAMINANTS

VOC EMISSIONS

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

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

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)

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

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

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 RH>=65%

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

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

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

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 mfr’s warranty

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

VOLATILE ORGANIC CHEMICAL EMISSIONS

• 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

COMPARISON OF VOC EMITTERS

EMISSION RATES

0200400600800

100012001400

FLO

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ING

W/

PO

LYU

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AN

EF

INIS

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PR

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SE

D W

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DC

AB

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TS

PE

RM

AN

EN

TP

RE

SS

SH

IRT

S(N

EW

)

PE

RM

AN

EN

TP

RE

SS

SH

IRT

S(W

AS

HE

D)

FIB

ER

GLA

SS

INS

ULA

TIO

N

MIC

RO

GR

AM

S/S

Q M

/HR

DECAY OF EMISSIONS FROM FIBER GLASS

Formaldehyde Air Concentrations - Large Scale Chamber

0

0.05

0.1

0.15

0 5 10 15

Time, Hours

PP

M

THE PRACTICALITY OF ZERO VOC EMISSION MATERIALS

• 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

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

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

REFERENCE RESOURCES ON ALL ASPECTS OF INSULATION AND IEQ

• NORTH AMERICAN INSULATION MFR’S ASSOCIATION– www.naima.org

• Knauf Fiber Glass - www.knauffiberglass.com

– brad.omlid@knauffiberglass.com, – glenn.brower@knauffiberglass.com, 317-398-

4434, x8801

• ASHRAE Handbooks