Replace Chimney for Gas Furnace and Gas Hot Water exhaust

Old 03-20-12, 08:16 PM
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Replace Chimney for Gas Furnace and Gas Hot Water exhaust

We are adding an extension to the back of our house (basement and first floor). Currently the back middle of the house has a chimney for the gas furnace and gas hot water heater exhaust. If we don't remove the chimney then we will have to frame around the brick and have a large bump out in the new room on first floor.

Wondering what our options are for removing/replacing the chimney. We are considering removing chimney and replacing it with new stainless steel exhaust pipe. Wondering how much less the bump out in the room will be with a stainless steel exhaust pipe? What size is pipe is needed and how much clearance is needed from pipe to framing? And if it's worth it for the cost to remove existing chimney and add the new pipe?

Other options? We're also adding a another chimney for a wood burning fireplace - wondering if relocating existing gas furnace and hot water heater to exhaust near this chimney is a reasonable option.
Old 03-20-12, 08:32 PM
Join Date: Oct 2008
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Hi Jasper, Chimneys and more chimneys . One of the issues surfacing with the push towards more energy efficient homes is the incompatibility of natural draft appliances and air tight homes. If your furnace, water heater, and new fire place are or will be all sealed combustion appliances, you are all set. But many sealed systems don't use a chimney, but simply vent out the side of the house.

If your fireplace will be burning inside air, then drafting can become a problem. If that chimney will be on the outside of the house, even worse.

As for the furnace and water heater, if you haven't tightened up the house with air sealing measures, then little will have changed. But if you plan to soon make improvements, now would be a good time to think about new sealed systems and perhaps moving that chimney won't be an issue, simply remove it. More information if needed.

Old 03-24-12, 08:14 PM
Join Date: Jan 2012
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You can't vent solid fuel burning appliance in the same chimney as gas, at least not in Canada. You should redirect the money you are planning on spending on the
second chimney for the gas appliances and upgrade them. A high efficient furnace uses two two inch vents and will save you money in the long run. As for your water heater you can get a power vented model, that way you won't ever have to worry about down drafts and carbon monoxide.

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