Have to get humidity down: glass tops or canopy?

[wickedfrags]

Is a possibility, most likely with olders homes not equipped with powered direct vent equipment. Realistically unless the fan is located in very close proximity to the exhaust ducting, most fans do not draw enough air to reverse the flow of exhaust. That being said, if your pilot light keeps going out, you hay have a problem!

Fascinating about that code issue and the furnace interlock - any idea how many CFM this relates to?

Originally Posted by Delphinus

Need to be a little careful with this .. If you have negative pressure in your house then if there's any incomplete combustion in the furnace or hot water tank, carbon monoxide can be drawn into the house and not exhausted out the exhaust vent as normal. If you have a strong kitchen fan for example, code will require you to interlock it with your furnace so that you can't create a negative pressure in your house. A standard bathroom fan might not be enough to cause a problem but it's something to consider.