I made this post over at Knots and it was by good recommendation that I try here.
I have a gas-fired unit heater in my garage/Workshop, 30K Btu with a 3″ B-vent or double walled stack. There is water coming in looks like around the outside of the vent pipe when we get a heavy blowing rain. It amounts to a few drops on the floor enough to just cover the bottom of a five gal. Bucket.
On the roof, the vent pipe is not sealed to the roof flashing but the storm ring is sealed with what looks like gutter sealant. Should the vent pipe be sealed to the roof flash as well? I’ve received two options on this from two different contractors, one says yes it should and the other said no, “there should be movement because of the roof”.
Any ideas?
Paul
Replies
What kind of roof? Pitch?
What kind of stack cap?
How wide of flange on the storm colar?
Is the storm collar all the way down to the roof jack?
What's the rise on the roof jack? Is it installed upside down?
Is it the right jack for the pitch of the roof?
Can you tell if there is any water coming in on the inside of the stack? Only on the outside of the stack?
Can you see the inside of the roof jack from the underside? (looking up the stack from inside the attic) Any rust or corrosion on the stack or roof jack? How much daylight can you see? Has it always leaked from day one?
You can seal the stack to the jack as a plan "B" but wait there's more. You may have other problems that need addressing.
Who ever invented work didn't know how to fish....
Ok I'll see what I can Answer...
"What kind of roof? Pitch?" Three tab don't really know pitch.
"What kind of stack cap?" It has vertical louvers.
"How wide of flange on the storm collar?" 1"
"Is the storm collar all the way down to the roof jack?" Yes it is.
"What's the rise on the roof jack? Is it installed upside down?" 6" and no
"Is it the right jack for the pitch of the roof?" Top of jack is level.
"Can you tell if there is any water coming in on the inside of the stack? Only on the outside of the stack?" On the inside of jack
"Can you see the inside of the roof jack from the underside? (looking up the stack from inside the attic)" Yes, "Any rust or corrosion on the stack or roof jack?" No, "How much daylight can you see?" very little, "Has it always leaked from day one?" Yes.
There is no water coming in under the jack, just down the outside if the pipe.
"You can seal the stack to the jack as a plan "B" but wait there's more. You may have other problems that need addressing."
I really don't want to seal the stack pipe to the jack, only as last resort.
Thanks for the help,
Paul
Redo / caulk the storm collar as Piffin suggests. Sillycone can be corrosive to the metal and it doesn't like sustained heat.
See if you can find a wider flanged storm collar with a nut / bolt tightening arrangement. Limit the space between the the roof jack and storm collar but don't set down on the roof jack.
You should be fine.
Who ever invented work didn't know how to fish....
OK... I'll look for a wider collar, wrap around with nut/bolt, and then reseal with something that will take the temps. No silicone
Thanks again for the help.
Paul
Hi Paul, Good name you've got there. Where'd you find it?
;)
The fact that it leaks only a few drops and only when the wind blows suggests to me that the collar is too high above the top of flashing. Asd a general rule, I don't caulk the flashing to the pipe either but for diferent reason than mentioned. As the pipe heats and cools, that particular seal will be blown anyways.
Here's how I install a collar.
I wrap it in place as tight as I can and then slide it up a couple of inches. Then I use the best caulk for the job ( generally not silicone - it breaks free from metal after a few years) and run a bead around the pipe right under the collar and slide the collar back down into the caulk seal until it is close to touching the flashing. How close depends on how warm it is.
BTW, the roof flashing jack should be sized and trimed to fit snug to the pipe. If it is too loose, somebody was careless.
After sliding it into place, I run another tighter bead around the top of the collar.
Sometimes, wind can still send a couple drops of water up under the colar and down the shaft. It's not a perfect system.
Excellence is its own reward!
I see what you mean by installing the collar properly, I'm going up on the roof today and check. The collar looks like it's down all the way.
Thanks for the help,
Paul
By the way, Piffen, how would you protect blown in fiberglass when the b-vent needs to run through it on its way to the roof? Or is the b-vent rated to run through flammable material (I don't think it is)?
My plan is to center the 3"D b-vent in a 6"D piece of 16 gauge galvanized pipe, which will be long enough to provide a 1" air space between the b-vent and the inside of the 6" all the way through the insulation. Is that enough?
The 6" will be screwed to the firestop rim, which in turn will support the b-vent in the normal fashion. A little complicated because this is for a water heater dedicated to heating the slab in my shop, so I don't have a convenient chimney to patch into. Also the roof is hi-vee pole barn steel, and the ceiling is also pole barn steel. The center of the b-vent will be only 8 1/2 " in from the interior wall, because I want to locate the WH as close to the wall as possible, and that's by far the easiest place to do the cutting through the roof.
I'm a little worried about supporting this long piece of b-vent with just the firestop screwed to the ceiling steel, and whatever lateral support it gets from the roof jack. It will be like 8 - 10' total length, because it's so close to the eave I want to make sure won't backdraft 'cause it terminates too far below the level of the ridge. 4/12 pitch, trusses are 32 feet, including 12" overhang, I figure 6'4" above roof surface to meet the 2' over anything 10' away rule of thumb. That's alot of b-vent hanging up there in the wind. Think I should guy wire it?
Or should I just go out through a wall thimble and then vertically the appropriate amount, fastening to the fascia via approved clamp on the way up? Looks hick, but it is on the backside of the building and would save climbing around on a slippery metal roof, plus no roof penetration with associated leak threat.
Thanks for so generously contributing your skill and expertise to this forum!
Edited 11/6/2003 10:36:32 AM ET by johnnyd
I shield it in the same way in attic space for insulation. Just get a pioece of snap together with a diam large enough to maintain that inch of gap - two inches for hotter pipe on wood stoves.
You shouldn't need it that high for a 4/12 pitch. You want two feet above ridge or three feet above any point within ten feet. That would be 6'4".
OK, Maybe that would be 8' total. They make roof support collars that are a ring clamoed to the pipe with a couple of arms that tie back to the roof and look ugly as sin, plus you have to screw a hole through the shingles to install it. I have used one arm only and run it directly behind the pipe instead of the two off to both sides.
Since it is your own house, what you might do is try it wiothout the support braces until a good stiff wind tests it for you and then make a decision if you need it..
Excellence is its own reward!
Thanks, Piffen...
After going back and forth over this, I think I'm going to go through a wall thimble with technique per my edit, which you probably didn't get. Yeah, ugly as sin, but it is on the back side of the building, and if I do a neat job with everything square and plumb, I think it won't look too bad.
Thing about "testing the wind"...I don't live there yet, although some times it seems like it what with spending 3 - 4 hours most evenings, 12 hour Saturdays with an occasional Sunday thrown in for good measure...last thing I want is a separation in a b-vent joint, while I'm not there, while the WH is going full blast heating up the slab.
pictures of builidng in question attached...this is the FRONT side, and the pex/rebar build.
It is a bad idea to run B vent on the outside of a house. I have been called to jobs where the owner was KILLED by such a set up. It does not meet code because it is in a cold exposed area for too far. this creates a downdraft. Most inspectors will still pass it since they have no clue.
Each elbow reduces flow/draft which is also part of the problem. I assume yopu are refering to the cold air in the flue needing to reverse flow to get draft started..
Excellence is its own reward!
Not a house...just a garage/workshop which will have a baseline slab temperature of 55 - 60 degrees. No one will EVER sleep in there. I'll keep a really close eye and nose on this installation and change it out if necessary.
While I've got you, question about the GPM that I should be pumping at. This is a single zone, 3 - 250' wirsbo loops stapled to the 2" rigid under the 24 X 29 foot 4" thick slab. Has a Rehau (?) manifold and a Grunfos "medium head" three speed pump controlled via slab sensor and SP 30 Goldline unit. Heat source is a 50 gallon AO Smith propane WH.
Initial setup has the temp going in at ~100 degrees and coming out at ~ 80 degrees, running at 14 psi. Hardly needs to go on at all to maintain a slab temp of 55 degrees. Actually, the 10 -150 watt bulbs that provide overhead light warm the air temp up 4- 6 degrees in a 'couple of hours with outside temp at 20 degrees. R40 ceiling, R23 walls, no windows, two insulated garage doors, one man door. Purpose of the system is just to maintain a comfortable baseline temperature to work in, with a side benefit of helping to keep the well pressure tank, BIRM filter, etc, located in an adjacent room, from freezing.
The manifold has little red knobs on the return side that screw in and out, controling the pins, which in turn affect the GPM readings on the little floating meters right above the valves. When wide open, the meters read almost 2 GPM. What should I run them at? Are they intended to provide the right flow so you maximize the amount of heat passed to the slab, or to control the flow to individual circuits? Or both?
Should I run them wide open?
Not a house...just a garage/workshop which will have a baseline slab temperature of 55 - 60 degrees. No one will EVER sleep in there.
How about breathe?
I'll keep a really close eye and nose on this installation and change it out if necessary.
CO is odorless -at least use a good CO detector - the $40-50 type with an digital readout
_______________________
Albert Einstein said it best:
“Problems,” he said, “cannot be solved at the same level of consciousness that created them.”
Your mileage may vary ....
Thanks, I'll get one and let you know how it turns out.