You are right to be concerned. I believe the Illinois residential code is based on the 2018 International Residential Code which forms the core of most statewide building codes. The 2018 IRC requires a make-up air system be installed if the exhaust capability of a range hood exceeds 400 cubic feet per minute (cfm.) It's intended to prevent depressurization of homes and attendant back-drafting of vented appliances like gas hot water heaters, fireplaces, etc. Failure to install the required make-up air system will be an inspection "show stopper" for your final inspection and likely prevent your move in. Tell your builder to open the code book and have a look.

To reiterate many threads here: No air leaves the kitchen via its hood system that isn't replaced (made up) one way or another. The make-up air can be supplied by a deliberate MUA system (heated in Chicago), or via leakage paths in walls, ceilings, basements, and reverse flow in combustion appliances -- see Charles Ross Homes comment above. So even if there were no combustion appliances or fireplaces to back-draft and thus no safety hazard, there would still be a gag on the hood system causing the actual flow rate to be very low, even as moisture is pulled into walls and wall dust into the living area.

I suggest you search this forum and the HVAC forum for threads and comments related to MUA.

As a short-cut, here are back-drafting levels provided by another forum member.

Mechanical-Draft Appliances

Heating systems with fan-powered exhaust systems can withstand higher negative pressures than natural-draft appliances. Some types of fan-powered systems are much better than others, however. In order of effectiveness, the choices are:

* Sealed-combustion. Also called “direct vent,” these appliances draw all combustion and dilution air from outside. These can typically tolerate negative pressures in the range from 25 to 50 Pa.

* Power-vented. These draw their makeup air from indoors and are also called fan-assisted, forced-draft, or mechanical-draft. These can typically tolerate up to 15 to 20 Pa of negative pressure.

* Induced-draft. These have a small fan added for energy performance, not to overcome house depressurization. These can typically tolerate 5 to 15 Pa of negative pressure.

By comparison, an atmospherically vented furnace can back-draft with as little as 5 Pa of negative pressure, and a gas water heater will have spillage at 2 or 3 Pa. Fireplaces can start having problems at about 3 Pa. Canadian codes limit negative pressures in homes with atmospherically vented equipment to 5 Pa. U.S. codes do not currently address the issue (in a plainly spelled out "prescriptive" number).

1 pascal = 0.00402 inches, water column

1 atmosphere = 407 inches, w.c.

Thank you! I will search MUA in the threads. Our gas fireplaces are direct vent. So that sounds like a plus according to your comment. Thank you for the insight!

The potential for back drafting aside, range and cook top vent hoods are essential for removing moisture, odors, products of combustion (primarily from gas stoves, but if I'm cooking, I manage to produce those on any cooking appliance) and cooking by-products. If we want our homes to be healthy indoor environments, we need exhaust appliances that work properly, and, of course to use them when needed. I can't believe how many of my clients don't run the range hood when cooking and don't run the bath vent fan when showering.