Bathroom Vent is tied to ceiling vent in adjacent room

Question

I live in a bungalow with a bathroom on both levels. The bathrooms both have exhaust vents. Outside of each bathroom is a ceiling vent. The previous owner stuck towels in these to block them off. When I removed the towels I felt cold air (it's winter right now) falling down, so I put them back.

When I had them out, I could see the vent hoses go back towards the bathrooms. With the towels out I turned on a fan in the bathroom and I can feel air being blown by it to the vent outside of the bathroom. It seems like they are connected.

My question is this. What purpose do these vents serve? Is it okay to have them blocked? Should I be concerned?

I have electric heat, so I'm guessing that it might be a way to help bring in fresh air?

Any thoughts?

Bungalow was built in 1978 in Ontario, Canada.

The vent in my bathroom seems to be connected to a ceiling vent just outside of the bathroom. Why?

Answer 1

Yikes, this is really the first time I have ever heard of this configuration. Could this have been part of a previous central forced hot air system? It is not common to tie exhaust vents from a bathroom to any other living space. A dedicated exhaust fan vented to outdoors with a one way damper is a very important way to remove excess moisture from bathrooms and help prevent mold and mildew growth. It is not acceptable to vent a bathroom to another living space or into an attic. It is equally not right to tie this type of vent to any other air plenum. If you are feeling cold outside air through these vents, you are getting huge heat losses. There is no need to introduce outdoor air into your house intentionally unless it is done with specifically designed air exchange equipment in an extremely airtight designed house. I think you need to determine the routing of these "phantom" vents and come up with a plan to isolate the bath vents to the out of doors with a proper bathroom fan unit and block your heat form other areas from being wasted out an open plenum.