Bathroom Ventilation New Code

I heard another inspector say that the IRC was taking away windows as an option for bathroom ventilation and now they all have to have mechanical vents even if there is already a window that is +3sf. I can’t find it anywhere in writing. Is he crazy or is my googling not up to par?

P.S. Please no responses from haters.

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It’s not in the code in IRC 2021, Texas is on 2015 IRC

However, I always recommend fan exhaust even if it’s not required when window is present. Your buyer should know this and many don’t unless you explain it to them. Imagine opening a window where it’s 100F and humid outside to take a shower. What’s going to happen to all the humidity inside the bathroom? It won’t disappear magically. Same goes when it’s 10F outside here in North East, ladies won’t like that and will not open the window in the winter! Mechanical exhaust in a bathroom is very important for long-term performance.


50 CFM exhaust fan is required (minimum)

You are misreading the code. 50 CFM is the minimum rate when required to be installed. Bathroom fan is not required when properly sized window (per code) is installed.


R303.3 Bathrooms

Bathrooms, water closet compartments and other similar rooms shall be provided with aggregate glazing area in windows of not less than 3 square feet (0.3 m2), one-half of which shall be openable.

Exception: The glazed areas shall not be required where artificial light and a local exhaust system are provided. The minimum local exhaust rates shall be determined in accordance with Section M1505. Exhaust air from the space shall be exhausted directly to the outdoors.


You may need to check on this again. Windows don’t count for ventilation anymore.
This stuff changes to more controlled/measured mechanical ventilation systems. Washington for example has new IRC state amendment that requires whole house ventilation systems with supply fans or HRVs - (windows and gaps as fresh air intake not allowed). It will soon be everywhere.

Yes. This exception is for the window not for the exhaust fan.

Naturally you will have to check applicable state amendments, the OP is in Texas so whatever Washington is doing is not applicable.


I did check. When citing code you’re misreading perhaps I’m not the one that needs to do some double checking, just saying! The code is pretty clear and we’re discussing bathroom ventilation, not whole house – two different subjects.


Not sure what you are saying, please expand on this.

I’m trying to say that section 303 applies to natural light and ventilation requirements, then you have subsections for habitable rooms, bathrooms etc. The exception then applies to the window not to the exhaust. If the bathroom exhaust was optional it would have an exception in chapter 15.

Whatever you’re smoking, it’s goooood stuff :muscle: :sunglasses:


The reason for always recommending a bathroom fan has to do with not opening the window in the winter in my area. Little point in taking a shower in a warm bathroom if your going to let all the heat out from the window. Simon’s post stated a similar logic for warm humid climates. A bath fan solves both problems.


When doing some old house inspection the exhaust may be a recommendation but on the new builds exhaust fan in bathroom is required by the code.
I add it to the construction plans when missing to make sure contractors remember to put it in. It’s not an option.

Is that in Washington or Illinois?
The reason I asked your website has you located in both States.

In Washington now, but it’s the same in most places

I read this differently. To me it says, “no window required when there is an exhaust fan, therefore a fan is apparently not required when there is a window”


IRC R303.3 would not be needed and thus would not exist if an exhaust fan was always required.


Ok, let’s try to put the ventilation part aside for a minute and look at the same paragraph again but just on the light portion. Would you say that a light fixture is not required as long as the bathroom has a window?

I see your point, however lighting is covered in a different section of code. Where is bathroom ventilation covered? I am coming up pretty empty here.

So I went down the rabbit hole. I could not find it in IRC and IBC directs me to the IMC which directs me to chapter 4 which only contains this statement.

Section 402 Natural Ventilation

[BG] 402.1 Natural Ventilation

Natural ventilation of an occupied space shall be through windows, doors, louvers or other openings to the outdoors. The operating mechanism for such openings shall be provided with ready access so that the openings are readily controllable by the building occupants.