Draft Proposal CB-23 

This concept has been developed by the DOE Building Energy Codes Program (BECP) as a possible code

change proposal to the Commercial provisions of the 2012 International Energy Conservation Code

(IECC).   Interested parties are asked to submit any and all comments on DOE's initial concepts and draft

code change proposals. For instructions on submitting comments, visit:

www.energycodes.gov/development/commercial/codes/iecc/concepts/

Consolidate Damper Provisions (CB-23) 

Objective:  Consolidate all provisions associated with leakage rates, sealing, dampers, etc. of mechanical

system openings, vents, grills, etc. for air intakes, exhaust openings, stairways and shafts in one place in

the code.  

Suggested Code Change Proposal

Revise Section C402.4.5  

C402.4.5 Air intakes, exhaust openings, stairways and shafts. Stairway enclosures and elevator shaft 

vents and other outdoor air intakes and exhaust openings integral to the building envelope shall be 

provided with dampers in accordance with Section C403.2.4.4. s C402.4.5.1 and C402.4.5.2. 

Delete Sections C402.4.5.1 and C402.4.5.2

Delete Section 403.2.4.4 and replace as follows:

C403.2.4.4 Shutoff dampers. All outdoor air intake and exhaust openings and stairway and shaft vents

shall be provided with Class 1 motorized dampers with a maximum air leakage rate of 4 cfm/ft2

 of 

damper surface area at 1.0 inch water gauge when tested in accordance with AMCA 500D. Outdoor air 

intake and exhaust dampers shall be installed with automatic controls configured to close when the 

systems or spaces served are not in use or during pre-occupancy warm-up/cool down and setback. 

Stairway and shaft vent dampers shall be installed with automatic controls configured to open upon the 

activation of any fire alarm initiating device of the building’s fire alarm system or the interruption of 

power to the damper.

Exceptions: Gravity (non-motorized) dampers with a maximum air leakage rate of 20 cfm/ft2

 at 1.0 inch 

water gauge when tested in accordance with AMCA 500D when at least 24 inches in either dimension 

and 40 cfm/ft2 when smaller than 24 inches in either dimension shall be permitted as follows:

 1. In buildings not over three stories in height above grade. 

 2. In buildings of any height in climate zones 1, 2 or 3.
 3. Where the design outdoor air intake or exhaust capacity is not over 300 cfm. 

Gravity (non-motorized) dampers for outdoor air intakes shall be protected from direct exposure to wind.

Reason:  Clarification and ease of use of the code.  Currently shutoff dampers are covered in two places

(envelope and mechanical), which could potentially cause confusion.  There is a conflict in the current

code where exhaust and relief dampers are allowed to be gravity dampers no matter the building height

in the envelope section and only up to three stories in height in the mechanical section in Climate Zones

4‐8.  Because all exhaust and relief dampers are associated with mechanical systems, the more stringent

requirement in the mechanical section is retained.  The original intent of this requirement is to avoid

night exfiltration through any dampers during winter in tall buildings where stack effect becomes

significant.   This exfiltration is especially large for exhaust gravity dampers.  Dampers of all types have

the same leakage requirements and placing them in one section eliminates the possibility of

contradictory requirements.  Even when installed in the building envelope, the mechanical contractor is

typically responsible for installation and controls.  The proposed text locates all mechanical system

damper provisions in the mechanical section and provides the necessary reference to those provisions in

the thermal envelope provisions of the code.  Currently the damper class associated with 4.0 cfm/ft2

leakage is Class 1 (not Class IA, which is a 3.0 leakage rate) such that all dampers have the same

classification and leakage rate provision.    

Cost Impact:   There is no cost impact associated with this proposed change.