Venting Med. Efficiency Furnace And H2O Heater Thru Wall? - Building & Construction - DIY Chatroom Home Improvement Forum

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Old 03-31-2010, 03:14 PM   #1
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Location: Baltimore suburbs
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Venting med. efficiency furnace and H2O heater thru wall?

Not sure if this belongs in HVAC instead but I think it has more to do with building and construction so here goes:

My chimney needs some repair, it's not in super bad condition but the bricks are loose and it leaks a little into the attic under heavy rain. This vents the furnace and H2O heater, there is no fireplace. I thought about getting it fixed (either DIY or hiring a mason/chimney sweep) but then I did some research and thought hey what if I got rid of the chimney altogether. I wouldn't have to fix it anymore or worry about it leaking, I'd free up some space inside the house (the chimney runs in my kitchen but it's covered by wallboard). I'd have to remove the chimney but that should be easy with an air chisle. Then I'd have to patch the hole in the roof and shingles, ceiling and floors and do some remodeling inside.
Back to the main point, I'd have to vent the furnace and H2O heater somewhere. The furnace is a medium, 80% efficiency Carrier furnace. It was only replaced 3 years ago by the previous owners so it should still have alot of life left (so a high efficiency condensing furnace is not practical for me). I read the installation instructions on the unit and it says to vent through the roof. I'm wondering if it's possible to retro-fit some sort of fan to vent it through the side.

The H2O heater is older, probably around 10 years or so, but still should have some life left. It's not a power vent unit, but I wonder if those too can be retrofitted through the wall.

On a side note, here is a picture of the chimney. The crown is in bad shape but the below it and the flashing is pretty good (roof replaced 3 years ago). I don't think it'll be hard to fix.

Guess my main thing is to decide whether to fix the chimney and keep venting the furnace and H2O heater as usual, or abandon the chimney. Any pointers?


cbrc5eric is offline   Reply With Quote
Old 03-31-2010, 03:27 PM   #2
Join Date: Mar 2010
Location: Colorado
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Around here you can't "direct vent" out the wall unless it's a high effeciency unit. Retrofitting a fan sounds like asking for trouble...these are not gases that simply smell bad, they can kill people.


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Old 04-02-2010, 11:07 PM   #3
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Home Inspector

I would bet if you checked the installation instructions for the gas burning appliances it would recommend installing B-Vents inside your masonry chimney. The exhaust from the appliances are only about 350 degrees at the most as compared with about 800 degrees for the wood burning application it was built for. There is a large moisture content in the gas fuel exhaust that will be more likely to condense and damage your chimney with acidic, frozen water.

It is obvious that you need the services of a mason to repair the loose bricks and provide a proper chimney cap to keep things weather tight.

Also for proper draft you will want the chimney to be a minimum of three feet above the top of the roof.

Last edited by Alex Damgaard; 04-02-2010 at 11:09 PM. Reason: Added chimney height
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