Air Sealed Wood Stove Flue Pipe
kopecarch
| Posted in Energy Efficiency and Durability on
We have a sealed-combustion wood stove (Stuv Cube) installed in a recent build. It has a fresh air intake. We are getting set to do a blower door on the project, but I’m noticing that the flue pipe is very leaky. Sections are just dry fit together.
Are there any recommendations on manufacturers / products that are built better?
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Replies
All chimneys pipe I have seen connect the same way, air sealing is pretty much non existent.
Even a stove with a fresh air inlet will have much larger leaks elsewhere than what you would see through the seams of the pipe, not something I would worry about.
The bigger issue is a wood burner in a tight space. Not the easiest to get to work:
https://www.greenbuildingadvisor.com/article/flatrock-passive-winter-update
The usual idea with vent pipe for combustion appliances is that the natural draft is supposed to make everything “leak inwards”, so nothing gets out of the pipe because of that. You’re not supposed to tape the pipe joints, presumably because the tape can’t handle the heat. You could possibly use red silicone high temperature caulk, but I’m not sure it’s approved for this use so it might not really be an option either.
Bill
How has it been using your Stuv in the air-tight house so far? We're looking at purchasing one shortly (Stuv 16-68z) and would be great to get some feedback.
Apologies for the delayed response. The Stuv has been preforming well. Definitely recommend the combustion air intake. We're also monitoring air quality in the home with an AirThings device. PM2.5 ticks up when the door is opened to load the stove... but I've found that if I bump up the ERV rate - for a few mins both before and after loading the stove - it mitigates any indoor air issues from the stove. Otherwise, no adverse IAQ issues.
Also - that stove puts out a ton of heat.
One downside though is there's no way to throttle it... and so it's uncommon to keep a burn overnight.
kopecrach,
When we moved to BC 30 years ago it was very common to visit people with old wood stoves whose whole house smelled strongly of wood smoke, even when the wood stove wasn't on. I wonder what their IAQ was like?
For an airtight stove, the first floor single wall or double wall uninsulated vent pipe should be assembled using furnace cement to seal the joints, and the sections fastened together with sheet metal screws. The connection to the stove should also be sealed with furnace cement. The double wall ss insulated pipe sections that extend from your second floor and up through the roof are manufactured to fit tightly together, each manufacturer having their own design that doesn’t need any sealant.
Daniel
dfvellone,
It's been a few years since I installed one, but the first length of pipe off the top of the stove usually had a slip-sleeve so you can pull it down over the flange, or disconnect it to clean the chimney. I've never seen sealant used there.
At some point in the assembly a telescoping section of pipe aids in disassembly and reassembly and no furnace cement is used in the telescoping portion of the telescoping pipe, but the connections at each end should be sealed with furnace cement. At each cleaning, the cement gets removed and replaced when the chimney is reassembled. For a modern airtight stove it’s fairly critical to seal all the connections. Not so much a pre-EPA certified stove.