You're right to be skeptical. There's no specific code requirement I'm aware of that mandates a hardwired exhaust fan solely because a washer and dryer are in the same room as a toilet and shower. Let's break down the likely reasoning and what you should look for

Why the Inspector Might Say This (Even if indirectly):
Moisture Control is Key

The fundamental concern is moisture. Washers, dryers, showers, and toilets all contribute to humidity. Uncontrolled humidity can lead to mold growth, structural damage, and health problems.

Continuous Operation

The inspector likely wants the fan to be run for extended periods to properly remove moisture after showers, while clothes are drying, and generally to keep the humidity levels down. A hardwired fan with a timer or humidistat makes it easier to ensure continuous or scheduled operation.

The inspector is most likely implying that a plug-in unit may not be used, or used properly, and therefore a plug-in unit is less reliable in exhausting moisture from the room. Bathroom Fan Requirements

While not directly about the washer/dryer, building codes generally do require exhaust fans in bathrooms (rooms with toilets and showers). These requirements are usually based on airflow (CFM - cubic feet per minute) and how the fan is controlled.

Local Amendments

Building codes are adopted and often amended at the state, county, or city level. It's possible there's a very specific local amendment that the inspector is referring to, even if it's poorly worded.

Where to Look in the Codes


Building Code (not Electrical Code)

The requirements for exhaust fans are primarily found in the

International Building Code (IBC) or the residential equivalent International Residential Code (IRC) (or your local building code based on these). Look for sections on: Ventilation

This section will specify requirements for whole-house ventilation and specific rooms like bathrooms.

Moisture Control

Sections on preventing mold and moisture damage will indirectly influence ventilation requirements.

Bathroom Ventilation

Pay close attention to the CFM requirements and control methods allowed (switch, timer, humidistat).2.

International Residential Code (IRC)

Chapter 15 addresses Exhaust Systems, including: M1506 Clothes Dryer Exhaust. M1507 Mechanical Ventilation.3.

Electrical Code (NEC)

The National Electrical Code (NEC) addresses how the fan is wired, not whether it's required. Look for articles related to:

Wiring Methods

Permitted wiring types (NM cable, conduit, etc.)

Grounding

Ensuring the fan is properly grounded.

GFCI Protection

May be required if the fan is near the shower/sink area.

Dedicated Circuits

While not always required, a dedicated circuit might be recommended for a high-use appliance like a dryer.

Disconnecting Means

A way to safely disconnect power to the fan for maintenance. A hardwired fan will need a local disconnect switch.

Why a Plug-In Fan Might Be a Concern



Enforcement of proper use

The inspector is implying that a plug-in unit may not be used, or used properly, and therefore a plug-in unit is less reliable in exhausting moisture from the room.

Action Steps for Your Friend


Ask the Inspector for Specific Code Reference

The most important thing is to politely but firmly ask the inspector for the specific code section (e.g., IRC Section M1507.3) that mandates the hardwired fan. Get it in writing if possible. This forces the inspector to justify their statement.
2.

Review Local Codes

Download or access the adopted building codes and electrical codes for your friend's jurisdiction. Look for any local amendments that might be relevant.3.

Consult with Another Inspector/Contractor

Get a second opinion from another qualified home inspector or a licensed HVAC or electrical contractor. Explain the situation and ask them for their interpretation of the code.4.

Consider the Inspector's Underlying Concern

Even if the hardwiring is not strictly required, consider the inspector's point about moisture control. A good exhaust fan with a timer or humidistat is a wise investment, regardless of whether it's hardwired or plugged in.

In summary: It's unlikely there's a specific code mandate solely based on the appliances being in the same room. The concern is almost certainly about ensuring adequate and reliable ventilation to control moisture. Get the specific code reference from the inspector and investigate your local codes thoroughly. Flag for review