You are currently on the SWS 2017 legacy website. To view the current 2020 SWS website, please visit https://sws.nrel.gov.

The SWS 2017 website will be taken down in September 2022. You can access an archive of 2017 specifications from the 2020 SWS website under News & Updates.

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.

Multifamily Homes

	Title	Specification(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