Quality HVAC System Installation
Trust But Verify
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
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
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
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.
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
2009 IECC Duct Tightness Tests
� 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
Mandatory Requirements
SEAL DUCTS,
SAVE ENERGY
�Sealing ducts is a cost-effective
energy efficiency practice that gives
a high return on investment
HVAC System
� Poor design and installation increases energy
costs 10 –30%
� Sizing
� Design
� Installation
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
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
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
Duct Tightness Tests
� 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
Mandatory Requirements
Duct Tightness Tests
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
Mandatory Requirements
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
Ventilation
Outdoor air intakes and exhausts shall have
automatic or gravity dampers that close when
the ventilation system is not operating
Mandatory Requirements
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
Test Equipment
Testing at rough-in
Testing Post Construction
Testing
leakage
to outside
Testing leakage to outside
Mastic Sealant
Non-toxic – Low VOC
Green credits
Recommended Set time = 20 hours
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
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
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.
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.
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
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 barrier)
Vapor barrier should be complete. All holes, rips, and seams must be sealed with mastic or approved tape
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
Ts Ys & Ls
� Use mesh tape to
strengthen the joint where ducts of different
shapes meet.
� Seal all seams, even
manufactured ones.
Seal Gores
Sealant applied, still leaks
FABRICATION & INSTALLATION
GUIDELINES
� The air handler box should be air-tight
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.
Air Handler Leaks
Mechanical Systems & Equipment
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
Boots
� Seal all joints, including
manufactured seams.
� The transition between
the duct and boot may require mesh tape.
AIRTIGHT DUCT SYSTEM
All Duct Types
Register boxes should be sealed to the drywall or floor
with caulking or mastic
AIRTIGHT DUCT SYSTEM
All Duct Types
Register boxes should be sealed to the drywall or floor
with caulking or mastic
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
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
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
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
EXISTING HOMES
� In existing homes, not unusual to find
disconnected duct components, takeoffs
loose from ducts or ducts disconnected from
register boots
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
For Sealing Existing Systems
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.
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
� 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
� 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
Oversizing
What do you get when you combine cognitive
bias with inaccurate information?
Oversizing
� Old Rules of Thumb
� One Size Fits All
� US Department of Energy
� Most systems are oversized, increasing
installation cost for every house
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
Equipment Sizing
� 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
Mandatory Requirements
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
Oversizing
� Installation cost is higher
� Operating cost over life of equipment is
higher
� Can cause comfort problems
� Improvements in building envelope reduce
loads
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
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.
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
“It’s tough to make
predictions,
especially about
the future.”- Yogi Berra
U.S. Dept of Energy
30/30 Vision
2012 IECC 30% More Stringent 2006 IECC
More verification testing
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
Verifying Charge
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
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
Learn from the mistakes of others.
You can't possibly live long enough
to make them all yourself
--Sam Levinson
Thank you for participating
� Any questions
� Please complete your evaluation sheets so
we can plan future events
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