Having trouble figuring out how to meet the makeup air code requirement for kitchen fans?  Well, there may be a simpler, less expensive option on the table for you if you've already installed the exhaust hood.  If you haven't installed the range hood yet, you may want to look in to models that are already designed for the makeup air requirement.  

Before we go too much further, let's take a look at the code: 

M1503.4 Makeup air required. Exhaust hood systems capable of exhausting in excess of 400 cubic feet per minute (0.19m3/s) shall be mechanically or naturally provided with makeup air at a rate approximately equal to the exhaust air rate. Such makeup air systems shall be equipped with not less than one damper. Each damper shall be a gravity damper or an electrically operated damper that automa,cally opens when the exhaust system operates. Dampers shall be accessible for inspec,on, service, repair and replacement without removing permanent construc,on or any other ducts not connected to the damper being inspected, serviced, repaired or replaced.

M1503.4.1 Location. Kitchen exhaust makeup air shall be discharged into the same room in which the exhaust system is locat-ed or into rooms or duct systems that communicate through one or more permanent openings with the room in which such exhaust system is located. Such permanent openings shall have a net cross-sec,onal area not less than the required area of the makeup air supply openings. 

Wow, that sure is a lot to digest!  If your client is more in love with how the fan looks and not so much concerned about the cfm output then you may want to consider a simple reducer.  I've come across a few manufacturers (which I'm guessing most do) who already have a reducer on their list of exhaust fan accessories.  I've included a photo of the Miele R2000 exhaust fan reducer. 

If you have any questions and/or would like your fan tested to see if it meets the requirements give us a call or fill out this simple form and we'll reach out to you!