Exhaust vent cap problem?


  #1  
Old 01-03-04, 12:03 AM
M
Member
Thread Starter
Join Date: Jul 2003
Location: Florence, MT
Posts: 38
Received 0 Votes on 0 Posts
Exhaust vent cap problem?

I am annoyed at the way my bathroom exhaust is set up, and was going to make some changes.

First thing is the builder used flex conduit. Going to change to straight aluminum.

Second thing is the fan housing is mounted in such a way that the exhaust opening is pointed away from the roof cap, so the conduit makes a 180 degree bend in the first 6 inches.

I have no problem dealing with those two, but the next one has me stumped.

I discovered the conduit just pokes up into a rough hole in the roof. Over this sits the roof cap. The conduit is in no way attached to the roof cap, and when the fan is running I can feel the air blowing down around the opening back into the attic. I pulled the conduit out of the hole, there is no flange etc on the roof cap to clamp the conduit to even if I wanted to. The roof cap has no such capability. The best way to describe it is that I am looking up into a conical opening (small end on top, large end closest to me) and the conduit just seems to poke up near it. The opening on top has a smaller diameter than the ducting. No attempt was made to fit the conduit to the roof cap at all, I would say the conduit was stuck in there at least 2" from the opening.

What can I do about it now? When I put in the new straight tube how can I get it to mate to the underside of the cap (not enough room with the conduit in the hole to fit tools in the rough opening)?

Thanks

Mark
 
  #2  
Old 01-03-04, 06:49 AM
GregH's Avatar
Super Moderator
Join Date: Jan 2001
Location: Manitoba
Posts: 10,234
Received 65 Votes on 60 Posts
Mark:

It sounds like what someone has done is shoved the discharge of the exhaust into an existing attic vent.
You need to purchase and install a proper exhaust fan roof vent with a backdraft damper.
To avoid cutting another hole in the roof you could look at an under eve vent.

Don't remove the existing vent as your attic needs the air change.
 
  #3  
Old 01-04-04, 10:55 AM
M
Member
Thread Starter
Join Date: Jul 2003
Location: Florence, MT
Posts: 38
Received 0 Votes on 0 Posts
I hate to say it, but you are wrong (and right). No-one shoved the discharge conduit into an existing attic vent- it was new construction!

I suspect that what you are telling me is that the builder (or Heating/Ventilation sub-contractor) used inappropriate materials to do the job. That the so-called "roof cap" was not designed to work as a "roof cap" for a bathroom fan exhaust! It sounds like it is just a plain old attic vent (from the outside it looks like a mushroom).

I also noticed that just downslope from this roof vent, where two pieces of the roof sheathing (plywood) abut, debris (pieces of sawdust, chewed up pieces of plastic etc) have fallen in a neat row directly underneath the 1/8" gap between the two pieces of plywood. Would I be correct in assuming that the bathroom exhaust steam has been condensing on the metal attic vent and trickling down the roof under the felt and shingles, carrying building debris with it, to fall between the two pieces of plywood? The vent is approximately 18" upslope from this join.


I am starting to get pretty angry at the shortcuts our builder apparently took.

Mark
 
  #4  
Old 01-04-04, 11:31 AM
GregH's Avatar
Super Moderator
Join Date: Jan 2001
Location: Manitoba
Posts: 10,234
Received 65 Votes on 60 Posts
Mark:

In normal house construction one of the first things to be done is the installation of the roof shingles and because the roofer will often install the attic vents they were probably in place when the exhaust fan guy did his thing.
Can't say for sure but if the exhaust fan installer put in the roof jack he would have more than likely used the proper type.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: