HVAC Install Trust But Verify - PDF

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


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


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


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


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.


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


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

HVAC Install Trust But Verify - PDF

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