Home & Garden

Bathroom Exhaust Venting In Attic

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[OP]
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Dec 29, 2013
4 posts

Bathroom Exhaust Venting In Attic

Hello RFD,

New user here, long time lurker. I always read through the Home and Garden looking at the great advice people provide but now I find myself in a situation where I myself am looking for some input. We recently moved into a detached home in the GTA. Today I decided I should check out the attic to make sure everything looked okay (no leaks etc.). I know the bathroom vents were put in very recently by the past owners so I wanted to see how they were vented out. From past reading I know it should never be done into the attic itself. Low and behold, I found that the exhausts for the upper level bathroom as well as the master bedroom bathroom are both simply being vented into the attic. The bathrooms are adjacent to one another (as is in most houses) and the vents are simply blowing moist air into the attic space. In the picture you can see that the ducting on the right from the upper level bathroom is just taped onto a roof joist and open on one end. (Tape not visible in picture, it is behind the joist blocking the view). The master bedroom bathroom ducting on the left hand side is sitting on the insulation just venting out. Luckily on my part, the upper level bathroom has not been used, so there has been no moist air escaping that duct. However, the master bedroom shower has been used and I'm not sure if there is any damage. From the pictures I took, I could not see any. The house is about 25 years old.

First glance towards the bathrooms location from the attic entrance (ignore the big duct right in front, it is unrelated):
http://i.imgur.com/EqyS5r4.jpg

Close up to the duct work exhausting both of the bathrooms into the attic space:
http://i.imgur.com/Q07ZSJW.jpg

From what I could tell, the roof does have four or five vents that I think from my reading serve to circulate and remove humid air from the attic. Similar to this from google: http://whitmerdecks.com/gallery3/var/re ... 1365988255

What is the best next step? Should these bathroom be vented directly through the roof with their own dedicated vents? Or through the side of the house? Can the ducting be connected to the existing roof vents or should those be left alone? How much would I be looking to spend for this kind of work? Any other comments or tips/feedback are much appreciated.
22 replies
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Feb 3, 2005
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I had to deal with this type of situation in a home also. I cut holes in the roof and put in vents for 2 bathrooms, a laundry room and the kitchen range vent. The laundry vent is the trickiest as I also put in an extra lint filter to avoid blowing lint onto the roof, and it had to be solid metal duct (I also used solid duct for the range hood vent).

The duct in the attic should also be INSULATED! Yours is not. I do know people who just got the duct up close (within a foot) of the regular roof vents and they seem to be doing ok - but that definitely isn't correct or to code.

If you are lucky, you would have a flat side of the house that you could vent out of of (as opposed to flat/shingled roof), but you probably don't have that luxury.
[OP]
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Dec 29, 2013
4 posts
That's interesting - are the holes susceptible to water leaking through the roof and into the attic? I'm assuming if done correctly water leakage isn't a problem, but then again there is a hole in the roof after all. Do you know if its a good idea to join the two ducting from each bathroom together and then duct out a single vent through the roof? Or will I have to have TWO new holes separate from one another for each bathroom? Also, you're right - no flat side in the attic as its all sloped.

Forgive my ignorance but I'm not a very handy person at all. What kind of insulation would be suitable for the ducting? Would something like this suffice?:http://www.homedepot.ca/product/reflect ... x25/902353

Would it be a good choice to stop using the bathroom fan until I have this issue fixed?
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Oct 19, 2007
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Eska1964 wrote: Hello RFD,

New user here, long time lurker. I always read through the Home and Garden looking at the great advice people provide but now I find myself in a situation where I myself am looking for some input. We recently moved into a detached home in the GTA. Today I decided I should check out the attic to make sure everything looked okay (no leaks etc.). I know the bathroom vents were put in very recently by the past owners so I wanted to see how they were vented out. From past reading I know it should never be done into the attic itself. Low and behold, I found that the exhausts for the upper level bathroom as well as the master bedroom bathroom are both simply being vented into the attic. The bathrooms are adjacent to one another (as is in most houses) and the vents are simply blowing moist air into the attic space. In the picture you can see that the ducting on the right from the upper level bathroom is just taped onto a roof joist and open on one end. (Tape not visible in picture, it is behind the joist blocking the view). The master bedroom bathroom ducting on the left hand side is sitting on the insulation just venting out. Luckily on my part, the upper level bathroom has not been used, so there has been no moist air escaping that duct. However, the master bedroom shower has been used and I'm not sure if there is any damage. From the pictures I took, I could not see any. The house is about 25 years old.

First glance towards the bathrooms location from the attic entrance (ignore the big duct right in front, it is unrelated):
http://i.imgur.com/EqyS5r4.jpg

Close up to the duct work exhausting both of the bathrooms into the attic space:
http://i.imgur.com/Q07ZSJW.jpg

From what I could tell, the roof does have four or five vents that I think from my reading serve to circulate and remove humid air from the attic. Similar to this from google: http://whitmerdecks.com/gallery3/var/re ... 1365988255

What is the best next step? Should these bathroom be vented directly through the roof with their own dedicated vents? Or through the side of the house? Can the ducting be connected to the existing roof vents or should those be left alone? How much would I be looking to spend for this kind of work? Any other comments or tips/feedback are much appreciated.

You are right this needs to be properly vented through the roof or side wall. I had a bathroom fan installed, and used a dedicated roof vent and insulated 6" duct:

http://www.ventilation-maximum.com/Engl ... traps.html (CT-6)
http://www.homedepot.ca/product/flexibl ... oot/959965

Very important - try and route the flex duct as straight as possible such that the total length and number of turns are minimized (and avoids sharp turns and kinks).

Good luck!
[OP]
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Dec 29, 2013
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wally_walrus wrote: You are right this needs to be properly vented through the roof or side wall. I had a bathroom fan installed, and used a dedicated roof vent and insulated 6" duct:

http://www.ventilation-maximum.com/Engl ... traps.html (CT-6)
http://www.homedepot.ca/product/flexibl ... oot/959965

Very important - try and route the flex duct as straight as possible such that the total length and number of turns are minimized (and avoids sharp turns and kinks).

Good luck!
Thanks, all good points that I've noted. Would this be able to be done by a contractor or will I have to contact a roofer? And if so, would anyone be able to do this at this time of year when there is snow and ice everywhere? I'm assuming at this point I would have to wait until spring time rolls around and there is no risk of falling.
Sr. Member
May 14, 2007
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Ottawa
Eska1964 wrote: Thanks, all good points that I've noted. Would this be able to be done by a contractor or will I have to contact a roofer? And if so, would anyone be able to do this at this time of year when there is snow and ice everywhere? I'm assuming at this point I would have to wait until spring time rolls around and there is no risk of falling.
Yes, stop using the fans. Moisture in your attic is bad for your insulation, and can cause mould.
No, the two fans can't share a single vent.
No, you can't re-use your existing vents.
If there is a vertical exterior wall in your attic, it is easiest to go out that way (instead of through the roof), but it isn't a big deal to go through the roof.
If it is going through the roof, wait till spring. If it is going out through a vertical attic wall, it can be done now.
I would look for a hvac contractor. A roofer isn't going to want to run your ducts, but an hvac guy can install roof vents if necessary. He will also ensure the ducts are properly insulated. He might go with new pre-insulated flexible ducts (easier to install) or rigid ducts that he insulates with duct wrap insulation (bit more work but better airflow)
Sr. Member
Jan 8, 2011
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Toronto
To add to the above posts, you can terminate through a wall, the roof or the soffit. There are vents designed for all three purposes. Use insulated vent pipe to prevent condensation in the attic space. You can purchase insulated flex pipe in 4", 5" and 6" sizes from any home store.
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Backlight wrote: To add to the above posts, you can terminate through a wall, the roof or the soffit. There are vents designed for all three purposes. Use insulated vent pipe to prevent condensation in the attic space. You can purchase insulated flex pipe in 4", 5" and 6" sizes from any home store.
Do NOT vent through the soffit, it will bring humid air back into the attic
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Nov 2, 2005
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Backlight wrote: Use insulated vent pipe to prevent condensation in the attic space. You can purchase insulated flex pipe in 4", 5" and 6" sizes from any home store.
The insulation is to try to prevent condensation forming in the vent pipe itself resulting in the possibility of drip back into the fan and bathroom.
wally_walrus wrote: Do NOT vent through the soffit, it will bring humid air back into the attic
Not sure what code says about this but I've noticed a number of custom $1m+ homes built very recently around here using soffit vents. Of course, vented soffits all round is way more than is actually required and maybe they're bringing it out through a non vented section.
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Jan 8, 2011
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dirtmover wrote: The insulation is to try to prevent condensation forming in the vent pipe itself resulting in the possibility of drip back into the fan and bathroom.
The insulation will prevent condensation on both sides of the pipe depending on the season.
dirtmover wrote: Not sure what code says about this but I've noticed a number of custom $1m+ homes built very recently around here using soffit vents. Of course, vented soffits all round is way more than is actually required and maybe they're bringing it out through a non vented section.
It is permitted by code, most new home builders vent through the soffit. I'd say the best bet is through a wall. Roof vents have a higher probability of leaking and getting plugged with snow.

If it was my house I would go, wall vent, soffit vent and then roof vent (in that order).
Sr. Member
Jul 7, 2010
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burbs
wally_walrus posts are spot on. i had roof vents added when i reno'd my bathrooms and i connected them myself with the insulated flex pipe as well.

OP - not sure what you can do in the middle of winter but when it warms up call roofing company and get them to put in 2 vents like in wally_walrus link. then get someone to hook up the insulated flex line. depending on the roofer the vents should cost you between $300-$500 to install.

in the mean time i would use your bathrooms but keep hot showers to a minimum. not very practical to not use 2 bathrooms for another 2 months, unless you have a 3rd bathroom you can use...
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aubgray wrote: wally_walrus posts are spot on. i had roof vents added when i reno'd my bathrooms and i connected them myself with the insulated flex pipe as well.

OP - not sure what you can do in the middle of winter but when it warms up call roofing company and get them to put in 2 vents like in wally_walrus link. then get someone to hook up the insulated flex line. depending on the roofer the vents should cost you between $300-$500 to install.

in the mean time i would use your bathrooms but keep hot showers to a minimum. not very practical to not use 2 bathrooms for another 2 months, unless you have a 3rd bathroom you can use...
Or you can open a window, not ideal obviously
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ChzPlz wrote: Yes, stop using the fans. Moisture in your attic is bad for your insulation, and can cause mould.
No, the two fans can't share a single vent.
No, you can't re-use your existing vents.
If there is a vertical exterior wall in your attic, it is easiest to go out that way (instead of through the roof), but it isn't a big deal to go through the roof.
If it is going through the roof, wait till spring. If it is going out through a vertical attic wall, it can be done now.
I would look for a hvac contractor. A roofer isn't going to want to run your ducts, but an hvac guy can install roof vents if necessary. He will also ensure the ducts are properly insulated. He might go with new pre-insulated flexible ducts (easier to install) or rigid ducts that he insulates with duct wrap insulation (bit more work but better airflow)
You can make this possible by purchasing an inline fan. I have a Panasonic inline Whisper series setup in my master bathroom. One ceiling inlet near the soaker tub/toilet and one inlet close to the shower stall. Each inlet has its own duct which merges to a central duct attached to the fan/motor itself. The exhaust is eventually released through a single roof vent.

[IMG]http://hostedmedia.reimanpub.com/TFH/St ... BAT_02.JPG[/IMG]
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hitman_24 wrote: Or you can open a window, not ideal obviously
Its not ideal but its better than nothing. I would buy a small fan and use it with the window open to blow out the humid air until you fix it right.
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Jun 11, 2005
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I just re-read the op post and it looks like the vents have been like that for 25 years. I`m no expert but using the shower till the spring isn`t a big deal considering it it looks like it has been the same for 25 years.
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Sep 30, 2006
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antigua1999 wrote: I just re-read the op post and it looks like the vents have been like that for 25 years. I`m no expert but using the shower till the spring isn`t a big deal considering it it looks like it has been the same for 25 years.
OP mentioned that the bathroom vents were very recently installed by the previous owner. Sounds like the bathrooms had no vents at all until shortly before the house was sold.
Eska1964 wrote: New user here, long time lurker. I always read through the Home and Garden looking at the great advice people provide but now I find myself in a situation where I myself am looking for some input. We recently moved into a detached home in the GTA. Today I decided I should check out the attic to make sure everything looked okay (no leaks etc.). I know the bathroom vents were put in very recently by the past owners so I wanted to see how they were vented out. From past reading I know it should never be done into the attic itself. Low and behold, I found that the exhausts for the upper level bathroom as well as the master bedroom bathroom are both simply being vented into the attic. The bathrooms are adjacent to one another (as is in most houses) and the vents are simply blowing moist air into the attic space. In the picture you can see that the ducting on the right from the upper level bathroom is just taped onto a roof joist and open on one end. (Tape not visible in picture, it is behind the joist blocking the view). The master bedroom bathroom ducting on the left hand side is sitting on the insulation just venting out. Luckily on my part, the upper level bathroom has not been used, so there has been no moist air escaping that duct. However, the master bedroom shower has been used and I'm not sure if there is any damage. From the pictures I took, I could not see any. The house is about 25 years old.
[OP]
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Dec 29, 2013
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Thanks guys for the very helpful input. Yes, the fans were installed recently as I mentioned in the first post. I'm glad I found it early before any serious damage took place. I'll take a look for a vertical wall that they can be vented through as I'd prefer that than the roof. I'm thinking maybe I can have someone come by and temporarily move the ducts closer to one of the existing vents, just so that any moist air that does happen to come through won't get trapped in the attic space. Then in the spring I can have someone do a permanent fix. Does anyone have any reliable contacts that can help with this? Everyone's help is much appreciated.
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Eska1964 wrote: Thanks guys for the very helpful input. Yes, the fans were installed recently as I mentioned in the first post. I'm glad I found it early before any serious damage took place. I'll take a look for a vertical wall that they can be vented through as I'd prefer that than the roof. I'm thinking maybe I can have someone come by and temporarily move the ducts closer to one of the existing vents, just so that any moist air that does happen to come through won't get trapped in the attic space. Then in the spring I can have someone do a permanent fix. Does anyone have any reliable contacts that can help with this? Everyone's help is much appreciated.
By the sounds of it they were never installed properly this time or when the house was built. Why would they be installed properly when the house was built and then recently installed wrong dosen`t make sense.
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antigua1999 wrote: By the sounds of it they were never installed properly this time or when the house was built. Why would they be installed properly when the house was built and then recently installed wrong dosen`t make sense.
probably didn't have them at all before, they probably use to just open a window when showering to vent the moisture out.
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May 18, 2011
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In a related question. I am looking to put a 2 piece bathroom in my basement. Do you think I really need a vent since there is not going to be any bath or shower?

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