I'm considering installing gas logs. I have the option of vented or ventless. I'm leaning towards vented, since these are mainly for aesthetics, I have a working chimney, and my wife is sensitive to the smells of ventless logs. However, I'm concerned about running gas logs and forgetting to open the damper. Carbon monoxide!

I understand that there are devices called damper clamps, which will force my damper to always be open far enough to be safe. Obviously, though, this will open my house to the outside air. Is it possible to quantify how much effect this will have?

Also, as a bonus question, can things (insect, birds, bats, reindeer, what have you) get into my house through an open damper?

  • 1
    Ventless is inherently dangerous, end of story. Don't even consider it!
    – iLikeDirt
    Commented Nov 2, 2014 at 1:12
  • 1
    I don't think there's any way to answer this with any degree of accuracy. Especially since you haven't said what climate you reside in.
    – Tester101
    Commented Nov 2, 2014 at 12:09

1 Answer 1


Simply, you are not authorized to use the fireplace if you are ever going to forget to open the flue. If you can start the fire with the click of a remote I'd highly suggest leaving it open if you think you might forget. Perhaps a motorized flue control is in order (ideally one with limit switches that deny gas flow until satisfied-open). A CO detector goes without saying I'd hope.

Offhand, I can quantify for you that almost every fireplace installed in a house, has a net loss for heat. Including some even while they're in use. Keep the flue and doors closed when it's not.

houselogic.com will answer your bonus question by making sure you have a chimney cap present which keeps animals, rain, and snow out of the chimney.

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