How to Inspect the Bathroom Exhaust

Another InterNACHI Inspection Article: “Inspecting the Bathroom Exhaust”](

Thanks Ben. Good article.


According to the International Standards of Practice, the inspector shall inspect mechanical exhaust systems in the kitchen, bathrooms and laundry area.


Article on laundry exhaust is coming soon.

I like it as well however how does one search for it later ?

I went here … and did not find it but did find …

Hope the new site design attends to the terrible search for otherwise wealth of info.

Hi, Bob.

Please try the new search feature. It works really well.
See screen shot. It’s there.

It’s now in

Interesting. Very few of the new construction homes up here uses metal or pvc ducts. They all use the well insulated flex ducts and have for years. Occasionally they use the metal / pvc when they exit out the gable end but most still go through the roof with the flex.

And when the vent hood is installed on capboard siding, it is installed on a mounting block with a drip cap as I posted here;

That picture is a real poor installation. :slight_smile:

Please explain why that is a poor installation.

The way that vent is installed, it is relying on caulking at the top behind the flange to keep out water. the sides are open and moisture has a direct shot in the wall cavity.

For the same reason on vinyl siding they came out with similar blocks. It is easier to maintain the rain screen.

On a mounting block for wood siding, it is easier and provides a better seal at the flange. :slight_smile:

We must be talking about a different picture. First I don’t see a vent. I see what will probably be a light fixture. Not sure why there would be NM cable sticking out the hole otherwise. There is a proper Z flashing at the top. The sides won’t be caulked until all the siding is fully installed…

Sorry if there is confusion. Different photo maybe? I was going off the link you posted.

I was talking about this picture;

And should be installed on a mounting block similar to what I posted in another thread.
Although a wire is sticking out, the installation would be the same.


Hmm. I never saw that top picture. Leak waiting to happen. Should have been installed like the bottom picture.

Came from this link that Ben posted;:slight_smile:

This is how I checked Bath room exhaust Lick the end of you flash light to help hold the paper . Always worked well for us.