Bathroom Backdraft

Users who are viewing this thread

Dvid

Member
Messages
62
Reaction score
1
Points
8
Location
Elkhart, Indiana
We have a new home and one bathroom fan in particular has horrible cold backdraft from outside.

The damper with the fan is angled at the top and bottom. It's not stuck. I suspect it is leaking in air or worse blowing open from the other side if enough air is hitting the flap. That particular corner of the house gets a lot of wind. The soffitt cover is not snug up against the soffitt. Even covering 3 of the four sides of the vent cover with tape doesn't eliminate the problem.

I removed the outside soffitt vent cover and there is a white plastic pipe attached to the flex duct. (See photo. I have temporarily closed the pipe.)

I thought about inserting a product like Continental Fan Manufacturing BDD100 Spring Loaded Backdraft Damper for 4" Ducting BUT the white plastic piece in the soffitt has a little lip to hold a screen guard and is less than 4" wide. Not sure it will work.

Home Depot makes a 1 way soffit vent, but it must go beneath the soffitt and it won't attach to the white plastic tube under the soffit. Both pieces are 4".

Is my only choice to get up in the attic and install something like a Fantech 9800000 RSK-4 within the flex duct line?

Thanks! I need expert help.
 

Attachments

  • Vent Piece.jpg
    Vent Piece.jpg
    83.7 KB · Views: 1,217

Smooky

In the Trades
Messages
2,299
Reaction score
152
Points
63
Location
North Carolina
I installed one for the kitchen exhaust, up in the attic, right above the ceiling. Mine is in the vertical section before it turns horizontal. I've never had a problem with it. My fan is an 8" inline fantech and all the pipe and fittings are 8" as well. I also have a flap where it exits the end of the house to keep birds out.

http://www.rewci.com/4dusplobadar.html

http://www.supplyhouse.com/Fantech-RSK4-RSK-Series-4-Duct-Backdraft-Damper

At joints that I thought I might need to take apart for cleaning etc. I used these clamps. They also help prevent noise since the fan motor is mounted in the attic. For all the other joints I used foil backed tape:

http://www.supplyhouse.com/Fantech-FC4-FC4-Mounting-Clamp-for-Round-4-Duct-Pair
 
Last edited:

Dvid

Member
Messages
62
Reaction score
1
Points
8
Location
Elkhart, Indiana
Thanks Smooky. I don't know if I'm going to be able to do the attic install. It's just so hard to get to and work in that area, plus I am concerned if the butterfly vent failed it would be hard to know and a pain to fix.

Wondering if I can attach something like this from Amazon to the existing housing (see picture in previous post) under the soffit, which I can't remove. Or maybe I could cut off part of the 4in pipe length of this product and inset it in the housing? Another option here, but I'd have to duct tape it to the existing housing.

Thanks. I need to get this vent back open but don't think I can get up in the attic to do it, just outside.

If helpful here is the vent I have now, but this page does not show the mount under the soffit:
 
Last edited:

Dvid

Member
Messages
62
Reaction score
1
Points
8
Location
Elkhart, Indiana
Thanks. I called the company that supplies the vent and they called the manufacturer. There is no additional option with a damper so... until spring when I can get a contractor to do a bunch of work (or learn how to remove outside soffit) I rigged something. I took a connector and bridged the existing vent lead and the spring loaded damper from Home Depot. Then I wrapped some bubble foil around the space in between and duct taped it. Not pretty but the air flows out and not in now.
 

Attachments

  • VentSoffit.jpg
    VentSoffit.jpg
    90.5 KB · Views: 952

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,770
Reaction score
1,190
Points
113
Location
New England
FWIW, I'm not a great fan of exhausting a bathroom vent under the soffit at all. The hot air will want to rise, and guess what, there's a horizontal shelf above, and on many soffits, there are also vents into the attic in conjunction with the ridge vent. You're just adding that moisture back into the structure. Out the roof, if a gable end is not possible, is my strong preference.
 

Dvid

Member
Messages
62
Reaction score
1
Points
8
Location
Elkhart, Indiana
Jadnashua,

Thanks for taking time to write. I'm the homeowner. I really didn't know that and am limited as to what I can do on my own. For today I'm just thrilled I don't have the backrdaft and can use my fan. I don't think I can change the type of vent myself to a roof vent, heck I couldn't even remove the soffit I'll have to hire someone.

Would you prefer to see a directional vent with a flap that opens pointing outwards past the gutter like this Lambro? Trick would be to find one with a spring loaded vent cover to keep that strong backdraft out.
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,770
Reaction score
1,190
Points
113
Location
New England
That one might work. There are lots of them installed where yours is. But, it's not uncommon to see paint peeling or other problems. Vinyl isn't as problematic.
 

Dvid

Member
Messages
62
Reaction score
1
Points
8
Location
Elkhart, Indiana
So discouraged. Even with my temporary solution I have cold backdraft coming in today!

The spring loaded damper is not frozen open.
I've been up in the attic and the flex duct is sealed fine at the fan.
There is plenty of blown insulation over the flex duct.
Any spots I disturbed it I put rolled insulation back over.

It is a windy day outside, but how in the world is cold outside air coming in. Even if there was a tear in the flex duct somewhere it is covered in insulation. I would think I would have little chunks of insulation or smell insulation but I don't.

Stumped. Any ideas? THANKS!
 

Dvid

Member
Messages
62
Reaction score
1
Points
8
Location
Elkhart, Indiana
Going to have a warm day tomorrow. Anyone from reading the past posts above have any ideas? Thanks so much!
 

Smooky

In the Trades
Messages
2,299
Reaction score
152
Points
63
Location
North Carolina
What exactly did you install? Is it in the horizontal pipe or what? Does it close by gravity? When it is closed does it completely cover the opening?
 

Dvid

Member
Messages
62
Reaction score
1
Points
8
Location
Elkhart, Indiana
What exactly did you install? Is it in the horizontal pipe or what? Does it close by gravity? When it is closed does it completely cover the opening?

Thanks Smooky.

Below is the white plastic housing for original soffit vent. It has four posts. How the original vent attaches is proprietary. The manufacturer does not make a spring loaded damper alternative, not does any other manufacturer make an alternate vent to attach to their housing.

Vent Piece.jpg

So I attached a 4" pvc bracket (really a plain inline backdraft preventer that I took the flap out of) inside those 4 posts. That bracket had four screw holes I used to make the connection secure. To that I attached a new spring loaded damper vent with a 4" connection from Home Depot and secured it with a clamp. This is just for a rough, temporary workaround. Then I wrapped some bubble wrap insulation around the gap for good measure and duct taped it shut.


VentSoffit.jpg

The new damper works as far as opening and shutting with the fan. There is no ice or anything opening the damper from underneath, BUT I still have massive backdraft.

We are supposed to get heavy winds tomorrow from the NW direction that makes this condition the worst. So as a test I plan on covering the damper vent at the bottom temporarily and leaving the fan off to see if the brackdraft is coming from the damper or some other connection abve. In the attic the fan and hose are covered in deep blown in insulation and I supplemented that with rolled insulation where I disturbed any previous insulation. I saw no tears in the flex duct and the connection at the fan looked good.

It's a mystery. Thanks for any ideas.
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks