jhqpzjg
Member
Hi Folks,
My shingles are being replaced soon due to hail damage and I wanted to take the opportunity to 'clean up' the south facing roof surfaces by eliminating vent pipe and bath exhaust fan penetrations. The purpose of this would be to make a future roof-top solar installation easier for a larger array.
So, the drain vents. I have 5 vents in the roof area in question. One is quite near the ridge so I was planning on leaving that one for the vent to outside. I believe I understand that I may terminate 3 of the remaining 4 vents in the attic with AAVs. I spoke with a building inspector for my city, who advised that they were permitted in the attic by code, and reminded me I needed to leave one vent open to atmosphere, and make sure the AAVs were at least 6" above the attic installation. The last of the 5 vents comes up from the basement, I believe, through an exterior wall, through a vaulted ceiling void space for a short distance, then through the roof deck.
First the attic accessible vents. I notice that AAVs have varying drainage fixture unit (DFU) ratings. I believe I've determined the DFU requirements of all my fixtures, with a total of 34 for the house. Because I can't be absolutely certain which fixtures are attached to which vents, how do I determine what DFU rating I need for each AAV that I use on the 3 attic accessible ones? I saw a Studor Mini-Vent that I believe had 160 DFU branch and 24 DFU stack ratings...not sure I understand why the stack and branch ratings are so different. One of the attic accessible vents comes up through the insulation where there is not enough room between the insulation and the underside of the roof deck to install an AAV with 6 inches of clearance between the AAV and the insulation surface. Would it be permissible to put in a 90 degree elbow where the vent comes vertically out of the insulation, run the vent laterally a few feet to where the roof is higher above the insulation, add another 90 degree elbow to take the vent up away from the insulation a few feet then finish with the AAV?
Next, for what I believe to be the lone basement vent. There is a bathroom group (tub, sink, toilet), a washing machine, and a small sink in what was previously a photography dark room. All are near each other on the same exterior wall of the basement. Could I access the vent line through the wall above all these fixtures, but still in the basement and put in an AAV to eliminate the through-the-roof vent? I understand it has to be 'accessible' and have air flow...it could be behind a mirror or vented access panel high on the wall.
Regarding the drain vents, are there other questions I should be asking? Other things to consider?
Not sure if this is a 'plumbing' issue but the other consideration I have are two bath exhaust fans. I will need to relocate both of these across the ridge to the nearby north facing slope of the roof, where no solar panels would be installed. Looks like they are 3" flexible metal ducting, un-insulated. I would have to increase the length of the ducting, no more than 10 feet, to get them to the north facing slope. Any issue with this increased length? Both of these are venting bathrooms on the second floor. Should they be insulated?
If photos would be helpful, I can provide some, just let me know what you'd like to look at. Thanks for any insight you can provide.
Jason
My shingles are being replaced soon due to hail damage and I wanted to take the opportunity to 'clean up' the south facing roof surfaces by eliminating vent pipe and bath exhaust fan penetrations. The purpose of this would be to make a future roof-top solar installation easier for a larger array.
So, the drain vents. I have 5 vents in the roof area in question. One is quite near the ridge so I was planning on leaving that one for the vent to outside. I believe I understand that I may terminate 3 of the remaining 4 vents in the attic with AAVs. I spoke with a building inspector for my city, who advised that they were permitted in the attic by code, and reminded me I needed to leave one vent open to atmosphere, and make sure the AAVs were at least 6" above the attic installation. The last of the 5 vents comes up from the basement, I believe, through an exterior wall, through a vaulted ceiling void space for a short distance, then through the roof deck.
First the attic accessible vents. I notice that AAVs have varying drainage fixture unit (DFU) ratings. I believe I've determined the DFU requirements of all my fixtures, with a total of 34 for the house. Because I can't be absolutely certain which fixtures are attached to which vents, how do I determine what DFU rating I need for each AAV that I use on the 3 attic accessible ones? I saw a Studor Mini-Vent that I believe had 160 DFU branch and 24 DFU stack ratings...not sure I understand why the stack and branch ratings are so different. One of the attic accessible vents comes up through the insulation where there is not enough room between the insulation and the underside of the roof deck to install an AAV with 6 inches of clearance between the AAV and the insulation surface. Would it be permissible to put in a 90 degree elbow where the vent comes vertically out of the insulation, run the vent laterally a few feet to where the roof is higher above the insulation, add another 90 degree elbow to take the vent up away from the insulation a few feet then finish with the AAV?
Next, for what I believe to be the lone basement vent. There is a bathroom group (tub, sink, toilet), a washing machine, and a small sink in what was previously a photography dark room. All are near each other on the same exterior wall of the basement. Could I access the vent line through the wall above all these fixtures, but still in the basement and put in an AAV to eliminate the through-the-roof vent? I understand it has to be 'accessible' and have air flow...it could be behind a mirror or vented access panel high on the wall.
Regarding the drain vents, are there other questions I should be asking? Other things to consider?
Not sure if this is a 'plumbing' issue but the other consideration I have are two bath exhaust fans. I will need to relocate both of these across the ridge to the nearby north facing slope of the roof, where no solar panels would be installed. Looks like they are 3" flexible metal ducting, un-insulated. I would have to increase the length of the ducting, no more than 10 feet, to get them to the north facing slope. Any issue with this increased length? Both of these are venting bathrooms on the second floor. Should they be insulated?
If photos would be helpful, I can provide some, just let me know what you'd like to look at. Thanks for any insight you can provide.
Jason
