The document provides information about properly installing HVAC systems according to quality standards and code requirements. It discusses the importance of sealing ductwork with mastic to reduce air leakage, properly sizing HVAC equipment using load calculation methods, locating ducts within conditioned space when possible, and performing duct tightness tests to verify quality installation. Installing HVAC systems according to these best practices can improve energy efficiency, indoor air quality, comfort, and performance while reducing operating costs over the life of the system.

1. Quality HVAC System Installation
Trust But Verify

2. Quality HVAC System Installation
The goal for a Heating, Ventilation and Air
Conditioning (HVAC) system is to provide proper air
flow, heating, and cooling to each room

3. Instructor
Barbara Collins
ERH West
Building Performance Consultant
Certified NAHB Green Building Verifier
Certified RESNET HERS Rater
Energy Star Homes Partner
Certified Environments for Living Verifier

4. Class Objectives
Understand HVAC system air leakage testing
requirements in the 2009 IECC
Recognize the benefits of sealing ducts for savings,
system performance and indoor air quality
Understand how ducts are tested for leakage
Identify resources for local building departments
Identify the best techniques to seal duct systems; what
inspectors should see on inspections
Understand the IECC requirements for sizing of HVAC
equipment

5. Current Code Requirements
Must comply with all aspects of UL181
standards
Fittings, joints & seams of duct system shall
be made substantially air tight by means of
tapes, mastics, gasketing or other means.

6. Ducts - IECC
Insulation (Prescriptive)
Ducts outside the building
envelope: R-8
All other ducts: R-6
Sealing (Mandatory)
Joints and seams shall comply with IRC,
Section M1601.4.1
Building framing cavities shall not be used as
supply ducts

7. 2009 IECC Duct Tightness Tests
Mandatory Requirements
All ducts, air handlers, filter boxes and building
cavities used as ducts shall be sealed (Section
403.2.2)
Duct tightness shall be verified by testing
Only Exception: Duct tightness test is not
required if the air handler and all ducts are
located within conditioned space

8. SEAL DUCTS,
SAVE ENERGY
Sealing ducts is a cost-effective
energy efficiency practice that gives
a high return on investment

9. HVAC System
Poor design and installation increases energy
costs 10 –30%
Sizing
Design
Installation

10. Home Energy Use
Residential energy use 22% of U.S. total
25% of carbon emissions in U.S.
Heating & cooling is 40 – 60 % of home
energy use

11. Why seal ducts
Leaks waste energy and money
Average system leakage
New construction 20%
Existing homes 30%
Duct sealing reduces heating and cooling
energy losses and saves money

12. Other Problems
Duct leakage reduces air flow, conditioned air
isn’t delivered to rooms which can cause wide
temperature swings between rooms
IAQ issues with return leaks drawing in air
from attics, garages, crawlspaces
Pressure differentials can cause excess
building air leakage and back drafting

13. Duct Tightness Tests Mandatory Requirements
Post construction tests
Option 1
Leakage to outdoors: ≤8 cfm/per 100 ft2 of
conditioned floor area
OR
Option 2
Total leakage: ≤12 cfm/per 100 ft2 of
conditioned floor area

14. Duct Tightness Tests Mandatory Requirements
Rough-in test Options
Option 1
Total leakage ≤6 cfm/per 100 ft2 of conditioned
floor area
OR
Option 2
If air handler not installed at time of test total air
leakage ≤4 cfm/per 100 ft2

15. Exceptions: Duct tightness test is not required if
the air handler and all ducts are located within
conditioned space
Thermal Boundary is also used to define whether
testing is required.
Insulation installed on underside of roof sheathing,
AHU and ducts in attic, can be considered within
thermal boundary

16. Ventilation
Mandatory Requirements
Outdoor air intakes and exhausts shall have
automatic or gravity dampers that close when
the ventilation system is not operating

17. Test Protocol
Pressurize the HVAC system, measure
CFM of air required to reach pressure
Test at a pressure differential of 0.1 in
w.g. (25Pa) across entire system,
including manufacturer’s air handler
enclosure

18. Test Equipment

21. Testing at rough-in

22. Testing Post Construction

23. Testing
leakage
to outside

25. Testing leakage to outside

26. Mastic Sealant
Non-toxic – Low VOC
Green credits
Recommended Set time
= 20 hours

27. More on Mastic
High strength adhesive compound
Usually applied by trowel, brush, caulking gun
or hand
3 types- water-based; solvent-based; and
two-component curing systems
Water-based is the safest and easiest to use
It performs as well and in some cases better
than the other 2

28. VOCs in mastics
Volatile organic compounds
In water-based mastics, the only volatile
compound is water which is inorganic
VOCs are infinitesimally small (not
recordable)
Water-based mastics pose a low health risk
compared to solvent-based and two-
component mastics
Safer for the user, better IAQ, greener

29. How to apply mastic
Step 1 - Clean Duct Surface
Wipe dust oil and grease from the duct surface
Step 2 - Apply the mastic
Gaps less than 1/4″, load brush with mastic
and coat entire joint with a continuous strip
Use brush end to work mastic into joint
Spread mastic at least one inch on each side
of the joint.
The mastic should be thick enough to hide the
metal surface of the duct.

30. Mesh for Gaps
If gap is larger than 1/4
inch use fiberglass
mesh too
If mesh is sticky on
one side, cut enough
to cover joint, press in
place, then completely
cover it with mastic.
If mesh does not have
a sticky side, apply a
thin layer of mastic,
press mesh into the
mastic, then apply a
finish layer of mastic.

33. AIRTIGHT DUCT SYSTEM
Boots and Cans
Seal seams with
mastic
Thin mastic will crack
Make seal permanent
Plug Don’t Paint
Thick as a Nickel = .077 in
1/16 inch = .0625 in

37. FLEX DUCT TO METAL
Flexible Ducts
Seal inner sleeve & outer
sleeve
Plastic strap holds the
inner liner firmly to the
duct or fitting.
Mastic seals liner to
connection and covers the
end of the liner
Use draw band to hold
outer sleeve (vapor Vapor barrier should be complete.
barrier) All holes, rips, and seams must be
sealed with mastic or approved tape

39. AIRTIGHT DUCT SYSTEM
Metal Ducts and Plenums, Duct Board
Boxes
Openings greater than 1/4 inch should be
sealed with mastic and mesh
Openings less than 1/4 inch should be
sealed with mastic
Special attention to collar connections to
duct-board and/or sheet metal; seal around
the connection with mastic

40. Ts Ys & Ls
Use mesh tape to
strengthen the joint
where ducts of different
shapes meet.
Seal all seams, even
manufactured ones.

43. Seal Gores

45. Sealant applied, still leaks

46. FABRICATION & INSTALLATION
GUIDELINES
The air handler box should be air-tight

47. AHUs & Plenums
Fill all openings for
wiring, plumbing and
refrigerant lines.
Seal all seams in the air
handler and plenums.
Tape around access
panels, so they can be
opened for service.

48. Air Handler Leaks

49. Mechanical Systems & Equipment

53. AIRTIGHT HVAC SYSTEM
Air handlers on platforms
May be located in a closet indoors
Framers must be told not to put plywood top
on before walls are sheetrocked (or duct
board) to underside of platform floor
All wall surfaces must be sheetrocked next to
and in platform
Seal all joints

54. Boots
Seal all joints, including
manufactured seams.
The transition between
the duct and boot may
require mesh tape.

56. AIRTIGHT DUCT SYSTEM
All Duct Types
Register boxes should be sealed to the drywall or floor
with caulking or mastic

57. AIRTIGHT DUCT SYSTEM
All Duct Types
Register boxes should be sealed to the drywall or floor
with caulking or mastic

64. SHEET METAL CONNECTIONS
Start the inner fitting into the outer fitting
Apply a 2” wide band of mastic to the exposed part of
the inner fitting
Fully seat the joint and mechanically fasten with
sheet metal screws or rivets
Apply a 2.5” wide band of mastic to the outside of the
joint covering the screws or rivets and joint gap
Allow at least 12 hours drying time before starting
system
Temperature and humidity conditions can vary,
longer dry times may be required

67. Locating ducts within thermal
boundary
Within thermal boundary means within
insulated space and within the air barrier
boundary.
Attics and crawlspaces can be but are usually
not conditioned space
Critical that space is truly indoors and sealed
from unconditioned areas
Multi-level dwellings more easily
accommodate ducts in conditioned space

68. Ducts in Unconditioned Space
Usually ducts are located in attics and
crawlspaces
Big temperature differences increase
conduction losses and loads
Long duct runs in attics lose 15%+ of cooling
capacity before end
Convection losses by leakage

69. Benefits of locating ducts in
conditioned space
Ducts can be smaller
May have shorter runs reduce pressure drop
and improve efficiency
Can reduce HVAC system costs by reducing
loads
Improve comfort
No Testing in 09 IECC

77. EXISTING HOMES
In existing homes, not unusual to find
disconnected duct components, takeoffs
loose from ducts or ducts disconnected from
register boots

78. For Sealing Existing Systems
Tools & Materials
Head lamp, hat with light, or flashlight
A work board to span joists in attics
Gallon pail and 2-3 caulk tubes of mastic
Caulk Gun, mastic brush, fin and plenum brush
Roll of mesh
2-3 pairs of latex gloves
2-3 cloths, can of coil and fin cleaner to wipe joints
clean before applying mastic and clean up
Utility knife and telescoping mirror
Pliers, screw driver and tin snips

79. Sealing Priorities
1. Disconnected components
2. Connections between the air handling unit
and the plenums
3. All seams in the air handling units and
plenums, takeoffs, boots, and other
connections, especially site-built items.

80. EXISTING HOMES
Leaks connected to the outdoors are more
important than leaks inside home’s thermal
envelope
Holes near the air handler are more important
than distant holes with relatively low
pressures
Supply system leaks waste more energy than
return system leaks
Furnaces

81. Remove tie holding duct
to connection
Roll back insulation and
outer cover
Seal inner core with
mastic and band
Roll insulation down
and vapor barrier/outer
cover
Put band and seal with
mastic

82. Wrap Ducts with insulation
Insulation may be installed over wet mastic
but do not move the ducts too much or mastic
seal could be damaged.
All duct support work should be done before
applying mastic
Wait 2 -4 hours and water based mastic will
be dry to the touch

88. Oversizing
What do you get when you combine cognitive
bias with inaccurate information?

89. Oversizing
Old Rules of Thumb
One Size Fits All
US Department of Energy
Most systems are oversized, increasing
installation cost for every house

90. Oversizing
Sizing example
2000 SF House with standard metal windows
w/ .75 U-Value and .88 SHGC and 20% duct
leakage
Calculated Sensible cooling load = 58880 Btu

91. Equipment Sizing
Mandatory Requirements
Load calculations determine the
proper capacity (size) of equipment
Goal is big enough to ensure
comfort but no bigger
Calculations with ACCA Manual J
protocol or other approved methods

93. Oversizing
Sizing example
Same 2000 SF house with Low-E windows
and tight duct system @ 5% leakage
Sensible cooling load = 43877 Btu
Average of 1-2” decrease in duct diameter
sizes

94. Oversizing
Installation cost is higher
Operating cost over life of equipment is
higher
Can cause comfort problems
Improvements in building envelope reduce
loads

95. Right Sizing
Costs less to install – saves builder money
Costs less to operate - not starting and
stopping all the time
Short cycling can cause bigger swings in
supply air, less comfort
Better humidity control

96. DESIGN HVAC SYSTEM
Loads and CFM Calculation
ACCA Manual J Load Calculation or
equivalent required
Calculate heat loss and heat gain for each
room
Total room loads to determine system
requirements.

97. Manual J –Load Calc
The local climate – ASHRAE 30 year average
Size, shape, and orientation of the house
Insulation levels
Window area, location, and type
Air infiltration rates
Number of occupants
Types and efficiencies of lights and major home
appliances (which give off heat)
ACCA - Air Conditioning Contractors of America
www.acca.org

98. “It’s tough to make
predictions,
especially about
the future.”
- Yogi Berra

99. U.S. Dept of Energy
30/30 Vision
2012 IECC 30% More Stringent 2006 IECC
More verification testing

100. A Quality HVAC System
Be properly sized to provide correct air flow, and
meet room-by-room calculated heating and cooling
loads.
Have sealed ductwork that will provide proper air
flow.
Be installed with a return system designed to provide
correct return air flow.
Have balanced air flows between supply and return
systems to maintain neutral pressure in the home.
Be properly charged with refrigerant

101. Verifying Charge

102. Ductwork
Single most important energy measure for
most homes- low hanging fruit
Locating inside conditioned space is optimal
Seal joints with mastic not duct tape

103. Equipment Size
Oversizing is common and expensive –
upfront and during life
Sizing properly can reduce cost and help pay
for increased cost of other efficiency features

104. Learn from the mistakes of others.
You can't possibly live long enough
to make them all yourself
--Sam Levinson

105. Thank you for participating
Any questions
Please complete your evaluation sheets so
we can plan future events