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Vent in furnace closet, can I cover it?

3308 Views 6 Replies 4 Participants Last post by  SeniorSitizen
We are getting a very cold draft coming from or Furnace and Hotwater closet. In this closet there is a grate covering a hole that leads directly to the under house crawl space. Is there a reason for this vent that is situated next to the hotwater tank and furnace? Can I cover it during the cold of winter to stop the cold air entering the house?

I would love to be able to cover it up, because the air pouring into the house is extremely cold, which causes the furnace to constantly run.

Thanks in advance.

ps. I can send a link to a video if you need more information.
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It sounds like they created an air path to provide the necessary combustion air for your furnace and water heater. Assuming that is the case, you need to review those requirements and come up with a better option, I'm not sure a crawlspace is an approved source. But in any case, a controlled source can be created or other options. But, no, don't just cover that opening.

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Cold weather air infiltration always comes in low and exits high, so a hole in the ceiling is just as bad, it's just that you done feel it directly.

When you describe this as a closet, red flags pop up as limited space always requires combustion air consideration. To note before I forget, you don't want to limit the source of air as the result can be backdrafting and carbon monoxide, really bad.

I'm assuming your furnace is older and naturally drafted, pictures will help. You can also load them to a photo sharing site and post the link here.

If naturally drafted, there are vent size and location requirements, floor and ceiling are not among them. How big is that closet? Natural gas I assume? And not brand new appliances, ie not sealed combustion.

A rough guide is "1 square inch per 1,000 BTU/hr input for each low and high vent". If you have a 100,000 btu furnace you would need 100 in² high and 100 in² low. That is two 10" x 10" vents. That assumes the door to that room is closed and is not louvered. You might be able to remove the door and then close those openings, however, I advise you wait for some of the hvac pros (much better than myself) to see what they say.

I see one was already here :)
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