5.3001.5 Ductwork and Termination Design—Low Rise

Topic: 
Forced Air
Subtopic: 
Design
Desired Outcome: 
Efficient air flow to all rooms is ensured by proper ductwork
For supporting material, see Referenced Standards and Building America Solution Center.
TitleSpecification(s)Objective(s)
5.3001.5a
Sizing

Ducts will be sized to deliver the appropriate amount of airflow (both supply and return) needed to satisfy the heating and/or cooling load of the building

Ducts will be sized using friction charts

ANSI ANSI American National Standards Institute, www.ansi.org / ACCA ACCA Air Conditioning Contractors of America, www.acca.org Manual D Residential Duct Systems or ASHRAE ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers, www.ashrae.org equivalents will be used for all residential ductwork sizing

ANSI ANSI American National Standards Institute, www.ansi.org / ACCA ACCA Air Conditioning Contractors of America, www.acca.org Manual Q Low Pressure, Low Velocity Duct System Design or ASHRAE ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers, www.ashrae.org equivalents will be used for all commercial ductwork sizing

Minimize static pressure

Maximize air flow

5.3001.5b
Air handler to return plenum

Return plenum will be designed in accordance with ANSI ANSI American National Standards Institute, www.ansi.org / ACCA ACCA Air Conditioning Contractors of America, www.acca.org Manual D or equivalent

Radius elbow fittings or square fittings with turning vanes will be used to direct return air when a 90° turn is required

Minimize static pressure

Maximize air flow

5.3001.5c
Air handler to supply plenum

Supply plenum will be designed in accordance with ANSI ANSI American National Standards Institute, www.ansi.org / ACCA ACCA Air Conditioning Contractors of America, www.acca.org Manual D or equivalent

Radius elbow fittings or square fittings with turning vanes will be installed to direct supply air

Supply plenum will be the same size as the air handler supply opening

Minimize static pressure

Maximize air flow

5.3001.5d
Building cavities used as ductwork

Building cavities will not be used as ductwork in new systems

In existing systems, building cavities will be sealed and tested

Maximize air flow

Minimize energy use

Safeguard indoor air quality

5.3001.5e
Reducers

Reducers between sections of different size ducts will be in accordance with existing standards based on duct material ( SMACNA SMACNA Sheet Metal and Air Conditioning Contractors' National Association, www.smacna.org , NAIMA NAIMA North American Insulation Manufacturers Association, www.naima.org )

Minimize static pressure

Maximize air flow

5.3001.5f
Supply branch run outs

Runs will be installed as short as possible

Minimize static pressure

Maximize air flow

5.3001.5g
Boots

If using flexible duct with straight boots, duct will be connected to boot with no bend

A rigid elbow will be used when a flexible duct changes direction

A rigid connector will be used when joining two pieces of flexible duct together

Minimize static pressure

Maximize air flow

5.3001.5h
Supply terminations

Terminations will be selected based on ACCA ACCA Air Conditioning Contractors of America, www.acca.org Manual T Air Distribution Basics

Minimize static pressure

Maximize air flow

5.3001.5i
Return grille sizing

Terminations will be selected based on ACCA ACCA Air Conditioning Contractors of America, www.acca.org Manual T Air Distribution Basics

Grille gross area will be equal to or larger than return box

Minimize static pressure

Maximize air flow

5.3001.5j
Manual volume dampers

Dampers will be installed as close to the trunk as possible while still being accessible to allow for adjustment after interior finishes are installed

Minimize static pressure and noise

Maximize air flow

5.3001.5k
Flexible ducts

Flexible ducts will not be bent more than 45° without rigid elbow

Minimize static pressure

Maximize air flow

5.3001.5l
Take-offs

Take-offs that create high turbulence will not be used (e.g., elbows with integrated dampers, scoops)

Take-offs will be installed onto the trunk in accordance with duct construction standards ( SMACNA SMACNA Sheet Metal and Air Conditioning Contractors' National Association, www.smacna.org )

Minimize static pressure

Maximize air flow

5.3001.5m
Fire dampers

Fire dampers shall be installed as required by applicable fire code

Minimize static pressure

Maximize air flow