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oldbuck52 10-16-2010 04:45 PM

furnace vent
Have a Tempstar furnace at our cabin that is vented thru sidewall with single wall galvanized pipe. Lots of problems with condensation backing up and furnace repairs. Could we vent up thru the roof with B-Vent pipe in a vertical application to eliminate condensation? No chimney is available.TIA

beenthere 10-16-2010 05:03 PM

Yes, you can. provided its not a 90%/condensing furnace. if it is a condensing furnace, then it should be vented with PVC pipe.

oldbuck52 10-16-2010 06:18 PM

furnace vent
it is not a 90% /condensing furnace. Would you use b-vent all the way up or just for the pass thru the roof? Could I replace the existing wall pass thru with b-vent and the insulate around it with a chaisse? Thank you!

beenthere 10-16-2010 06:23 PM

B vent the whole way.

Good chance your furnace is NOT approved to be side vented. Without the addition of a power vent. which would also require a barometric damper. Which causes more cold air to be drawn into the building.

yuri 10-16-2010 06:32 PM

You can go horizontal thru the wall with B vent turn up with a B vent 90 el and continue it up the side of the house and terminate it above the roof line. Need to be above the highest peak of the roof or 5 feet from the side of the roof so you don't get swirling winds downdrafting it and tripping the pressure switch. Then build a chase around it for cosmetic reasons. May be simpler and easier to go straight up thru the roof. Code requires a cleanout/inspection tee in some areas so you may need to have that outside instead of the elbow.

kenmac 10-16-2010 06:39 PM


Originally Posted by yuri (Post 517972)
Then build a chase around it for cosmetic reasons.

Can you believe
My area requires this chase to be insulated . They say it's cold enough here to still cause condensation problems.. I don't argue I just comply

yuri 10-16-2010 06:43 PM

They may be right. It is rare for chimneys to be run externally where I am but I have seen a few. Mids are running flue gas temps close to the dew point as it loses heat in the vent connector before it enters the chimney and more as it rises. I would not try it w/o insulating it and insulating it sounds like a good idea. A B vent is not insulated between the layers, just an air gap I believe, A vent is insulated I believe.

Michael Thomas 10-16-2010 08:32 PM


Outside (exterior) b-venting is not recommended by b-vent manufactures. When it must be done, installation is an insulated chase is recommended:

oldbuck52 10-17-2010 08:59 AM

could we install a new energy 90+ efficient furnace without running duct work to any specific rooms. The cabin is approx600SF on main floor with 400sf on second story. The existing furnace has only 2 hot air escapes, one blowing into crawl space and the other into main area of cabin. Could this same approach work with new 90+ or do we need to run major duct work under cabin? Thank you for your help.

beenthere 10-17-2010 09:05 AM

A 90% can be connected the same way

yuri 10-17-2010 09:16 AM

As long as it is not an expensive high end unit with ECM variable speed motor. They need ductwork to suck and work against. Overkill for a cabin. Why not go with an electric furnace. VERY VERY reliable and as complicated as a toaster. 10 kw unit is probably all you need. High efficiency units need a condensate drain and if the cabin loses heat/power failure that can freezeup and get damaged etc etc.

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