Commercial Duct Systems: The Current State of … Commissioning Group AIA Provider Number 50111116...
Transcript of Commercial Duct Systems: The Current State of … Commissioning Group AIA Provider Number 50111116...
AABC Commissioning GroupAIA Provider Number 50111116
Commercial Duct Systems: The Current
State of Regulatory Compliance,
Design & Best PracticesCourse Number: CXENERGY1622
Neal Walsh
Aeroseal LLC
April 13, 2016
Credit(s) earned on completion of this course will be reported to AIA CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request.
This course is registered with AIA
CES for continuing professional
education. As such, it does not
include content that may be
deemed or construed to be an
approval or endorsement by the
AIA of any material of construction or any method or manner of
handling, using, distributing, or dealing in any material or product._______________________________________
____
Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
This presentation will review key updates to the
ASHRAE 62.1 standard for ventilation and indoor
air quality, the SMACNA duct design manual for
energy efficiency and other related industry
guidelines. We will look at recent study results
that highlight the size and the scope of the
problems associated with building ventilation and
the direct correlation between duct leakage rates,
energy efficiency and indoor air quality.
CourseDescription
LearningObjectives
1. Regulatory compliance and air duct leakage standards associated with ASHRAE
62.1, the SMACNA duct design manual and other industry guidelines.
2. Current research on the prevalence of duct leakage in commercial buildings today
and the implications that this has for energy efficiency and indoor air quality.
3. Best practices for duct system testing and remediation.
4. Real-world examples of duct deficiencies and strategies used to mitigate the
energy inefficiencies that result.
At the end of the this course, participants will be able to:
Overview
• Air duct tightness and testing standards
• The Hole Truth about air duct tightness
• Best practices in air duct remediation
Air duct tightness and testing standards
ASHRAE 62.1 and Duct Leakage
Key to maintaining correct
building pressurization
Duct tightness effects
zone air quality
Minimum discharge air
calculation must include
duct leakage
Air duct tightness and testing standards
ASHRAE 90.1, IECC, IGCC and Duct Leakage
Test ducts operating at >3 inWG
Test no less than 25% of the
surface area of the duct
Air duct tightness and testing standards
IAPMO Guidance
Test 20%
Recommended procedure:
-- If fail: retest + additional 20%
-- If 2nd fail: 100% test
Air duct tightness and testing standards
SMACNA and Duct Leakage
Formula for calculating maximum permissible leakage:
Leakagemax = CL X P0.65 X SA
• Leakagemax = maximum leakage expressed in CFM
at test pressure
• SA = duct surface area expressed in units of 100 sqft
• P = test pressure expressed in units of inWG
• CL = leakage class specified by design engineer
Air duct tightness and testing standards
SMACNA Test Manual Inferences
Engineer must specify amount of duct to be tested
• Testing all the ductwork is too costly
• Little benefit from testing low pressure ducts
• Not required to test ducts operating < 3 inWG
Engineer must specify leakage class• Use the recommended values
• Assume an operating pressure of 2 inWG for
VAV high pressure systems and 1 inWG for CV
systems if not specified
A 10% difference between fan and diffusers is not
necessarily excessive
Air duct tightness and testing standards
Europe Test Criteria
Testing required on duct pressure
classes above 0.8 inWG (200 Pa)
• UK: no testing required on low
and medium pressure ducts
Recommended procedure:
• If fail: retest + additional 10%
• If 2nd fail: 100% test
Test 10%
EU 12337 strength and testing of circular metal ducts
Air duct tightness and testing standards
Emerging Trends
Less allowable leakage
Higher percentage of duct tested
- low and medium pressure testing
- 25 - 50 - 100
The Hole Truth aboutair duct tightness
What Happens When Ducts Leak
• Supply duct leakage short circuits system
• Longer to satisfy temperature
• Building and zone pressurization
impact air quality
T
The Hole Truth aboutair duct tightness
Top Ten Building Faults: By Cost
Source: Building Commissioning: A Golden Case For Reducing Energy Costs , E Mills, 7/09
The Hole Truth aboutair duct tightness
By The Numbers
• 30% - the average rate of leakage
in light commercial buildings1
• 10% to 20% - average amount of air
provided by supply fan that
never reaches the occupied
space2
• 75% - percentage of commercial duct
systems that leak 10% to 25%3
(1) Florida Solar Energy Center, California Energy Commission Studies
(2) Lawrence Berkeley Nat’l. Laboratory Studies
(3) ASHRAE Handbook, Duct Design Manual
The Hole Truth aboutair duct tightness
More Facts & Figures
• System leakage significantly increases building energy leakage1
• A leaking VAV system uses 20% to 35% more fan energy than a
tight system2
• A fan exhaust system with 20% leakage causes fan power to
increase 95%2
(1) ASHRAE Handbook, Duct Design Manual
(2) ASHRAE SPC 215P: MOT to Determine Leakage
Airflows and Fractional Leakage of Operating
Air Handling Systems
Best practices:Air duct remediation
Licking Heights School District
• 5 school buildings
• 4,000 students
Best practices:Air duct remediation
West K-2 Elementary School
• 7 year-old building
• 20% higher energy
consumption than
sister building 3 miles
away
• Severe comfort issues
• New AHU and boilers
• 20,000 sqft expansion
Best practices:Air duct remediation
Diagnosis
• Dual 40 HP motor
continuous operation
• Ceiling plenum
positive pressure
• Many rooms had no
supply air flow
• Existing leakage 55%
• Internal duct
insulation torn
Best practices:Air duct remediation
Constraints
• No disruption to students or staff
• Guarantee result
• Project completion over winter break
• Safe for application with staff in building
• Proof of repair
Best practices:Air duct remediation
Alternatives
External manual repair
• 12 weeks
• $350,000
• Repair main ducts only
• Demolish ceiling
• No verification
• No guarantee
Internal aerosol sealing
• $180,000
• 2 weeks
• No demolition
• Repair main and branches
• Performance verified
• Guaranteed results
Best practices:Air duct remediation
Results
• Completed during 2 week winter break
• Reduced leakage by 95%
• Ended comfort complaints
• $45,000 annual energy savings
• Operating on night setback
• AHU VFD operating at 65% winter;
85% in summer
Best practices:Air duct remediation
Process Overview
1. Connect equipment
2. Isolate AHU
3. Block registers
4. Pre-seal: benchmark
5. Seal: inject sealant
6. Post-seal: measure final leakage
7. Present certificate
Best practices:Air duct remediation
Certificate of completion
When we arrived
YOUR DUCTS HAD:
3,317 CFM of Leakage equivalent
After we finished
YOUR DUCTS HAVE
178 CFM of Leakage equivalent
This corresponds to a 95%
Reduction in Duct Leakage
Best practices:Air duct remediation
Sealant FAQsVinyl Acetate Polymer
- base of chewing gum, hair spray
- remains rubbery
Certified in accordance with UL 1381
- surface burning
- mold growth and humidity
- interior duct burning
- leakage reduction
- durability
Low VOC content
2 hours to cure
3-year guarantee
Best practices:Air duct remediation
Next Steps
• Tighter leakage standards
• Increased testing/verification
• 75% of existing buildings
have excessive leaks
• Duct leaks are a low-
hanging
opportunity
• Aerosol sealing is an
efficient
and effective method
This concludes The American Institute of Architects Continuing Education Systems Course
For More Information contact:
Neal Walsh, [email protected]