Stove Vent Exhaust Problem

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  #1  
Old 07-10-18, 02:09 PM
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Stove Vent Exhaust Problem

For the last 20 years I've lived in a home built in the 1950s. Due to a renovation before I moved in, the stove vent was simply covered over, sealed and made no longer available. They just used a piece of sheet metal to cover and caulk it. Just today I removed the sheet metal. Looking at the image, you'll see the vent comes out right at the slope of the roof line. The roof you see in the image is part of an addition that was built before I bought the house. My concern is that the first time I get a good rain, water will gush down into my vent. The outside vent housing is maybe 8x10", but only the top part of the vent is open, shown by the red rectangle, which is your standard 4x10 opening, I guess the vent was left open below as some kind of drip loop, so to speak.





Here's a view from the inside. The vent is already in the furthest top corner of the interior kitchen room:



I'm not sure what my best option is, so that's why I'm posting. My feeling is I should just move the vent up. Horizontal movement isn't really an option, but if I move up a foot or so, that will move me into my second story. From there, I can open up an upstairs bathroom wall for access and then and bring the ductwork up an out using a standard 4x10 exhaust vent. I'm not a mason. This doesn't thrill me as an option.

The other option I was wondering about would be just using the same hole addressing the issue on the exterior. Maybe I could use some kind of exterior duct work or shedule 40 piping to move things up and out of the way of the water run off? Something like this?



Any suggestions or comments greatly appreciated. Meanwhile, I'm headed outside to try to reseal the vent in case it rains.
 
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  #2  
Old 07-10-18, 03:04 PM
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Can you go out the wall that is just to the right in your first photo?
 
  #3  
Old 07-11-18, 07:21 AM
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Unfortunately, no. Looking at the interior photo, to the right side of the image, you'll see a wall. That's an interior wall shared with a bathroom. Looking back at the second exterior photo, the bathroom would be on the pop can side of the vent.

I see what you mean though as moving the vent just a few inches up or over would be enough to get it out of the path of the water draining off the roof.

Is there any interior vent configuration that would allow me to reconfigure the vent dimensions in order to place it just out of the reach of the water flow? Convert it to a square or circle? (see green box) It's just so close.



It's not a long run from the Stove to the exterior wall, maybe 4' from the point the fan vent enters the ceiling over the stove, but I may have to use unusual vent sizes, transition between round and rectangular and make more turns than I originally expected.
 
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Old 07-11-18, 09:23 AM
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I think you need to go more than a few inches above the roof to get above the majority of snowfalls in your area.

Can you extend the duct through the bathroom and out an exterior wall?
 
  #5  
Old 07-11-18, 11:35 AM
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First, thanks for your replies.

Good point about the snow. I can go up more than a foot towards the upstairs bathroom. I guess that's the only real solution.

As for the venting itself, it's going to be unorthodox. Looking back at the interior image, I'm actually going to need to sister that joist on the inside where the vent runs through, meaning it will be too narrow for a 4x10. Also, there's plumbing going through which means I can only use the bottom half of the joist lane, so circular duct would only make things worse. I happen to have what looks like 3x8 duct from a past project. I'm not seeing much outside of the standard duct sizes in my area, so I'll likely have to create my own adapters using duct metal tape/pop rivets/sheet metal screws.

My plan is to install a stove/fan vent for a standard 30" stove with a 6" diameter exhaust. This exhaust should mount right into the ceiling into my 3x8 duct using some kind of right angle 6" to 4x10 adapter (modified as needed). Next a 4' run to the exterior wall, 90 degree turn going up, another 2' vertical run up inside the wall, then another right angle out to an exterior wall vent. I've actually been looking at a number of online duct calculators, but I'm a bit confused by terms like duct velocity and friction loss. Is velocity more related to noise than actual function? I think 3x8 will be at least as good as a 5" diameter duct. Anyway, do you think such a vent can handle 400cfm or do you have any comments on how to run it?
 
  #6  
Old 07-11-18, 12:16 PM
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Friction loss in a duct is more an issue for longer duct runs. You will have resistance in your run but your duct will be short enough I wouldn't worry too much. In your situation you don't have many options so put in the biggest duct you can.

As for your brick work I would start keeping an eye out for bricks of the same size as yours. I would remove the grate at roof level and patch the brick work to limit the chance of water problems in the future. Over the years I have collected a wide variety of brick sizes & colors which I keep for doing repairs on my rental houses. Masons and handymen in your area might do the same and you could buy a few bricks or trade for a 6 pack.
 
  #7  
Old 07-12-18, 06:15 AM
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From calculations I've been able to do, I think I'll be okay for the duct length and size. This link might be helpful for anyone else coming across this thread:
https://www.cdicurbs.com/ductcal

My house is made out of that yellow brick painted white. I have some red brick laying around from old landscape projects. Is there anything wrong with just using that? Isn't one brick as good as another? As for my workmanship, I"m not too concerned if the mortar joints are a little wide or the brick pieces a little off, so long as is seals up nice. I'm painting over it anyway.

Thanks for the help. I think I've put this off long enough!
 
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Old 07-12-18, 07:50 AM
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From your photo those appear to be a non-standard or less common size so a standard brick may not fit. You can use other bricks but if they don't fit then you'll have to cut them as needed and the grout lines might not line up. But being high up and painted it's not the end of the world.
 
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Old 07-12-18, 01:36 PM
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Okie dokie. Thanks for the help.
 
  #10  
Old 07-14-18, 06:53 AM
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Wow... I canít believe this didnít get caught in the home inspection before you bought the house... that is some horrendously stupid work that is definitely handyman worthy. For you not to have mice and water damage is evidence of good living and in good favor with the man upstairs. Especially with the storms your area in renowned for. Iíd yank that out of there, close in the opening and extend it up three feet. Use the brick you remove to close in the lower opening. Get a good insured roofer to flash and seal in that area. Those areas are prone to leaks even when done right...
 
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