Expert: James Ball - 2/28/2010

Question
Hello,

I have two vented gas fireplaces which were installed to my home in 2007.  They were installed to existed (brick) fireplaces and do not have doors attached.

We recently had an energy audit performed and it revealed that the open flues sources of significant heat loss.  This is something we have noted/felt ourselves on a daily basis.

I understand that the flue needs to be open to a certain degree for safety (and possibly code) requirements.  However, based on an entry which appears on the final report of the energy audit, query whether the flue needs to be in the FULLY OPEN position, or if it can be only partially opened.  Following is quote from our energy audit final report:

"The most significant air infiltration to your home is through the chimney flues. This creates a significant source of heat loss as warm air rises in the chimney, or conditioned air is pulled out of the house.  Gas fireplaces with pilot lights are required to have an open flue to vent combustion gases when not in use.  However, it only requires the flue vent to be cracked open a few centimeters, and not full open as is the current case."

Above appears to indicate that the flue need only be "cracked" open; currently they are pretty much fully open with flue damper blocker significantly more than just cracked -- looks to be open about 4 inches.

Greatly appreciate any guidance/thoughts you could provide on the minimum recommended amount the flues should be opened.  I have no documentation and though I checked with the company whcih the previous owner used they were not at all helpful and turns out it is not a particularly reputable company in our area.  Based on great professional responses I"ve seen here I'm hopeful you can offer some sound advise.

Thanks and regards,
Tom

Answer
Hello Tom, read your owners manual for the logs (or contact the manufacturer) most gas logs come with a "clamp stop" that keeps the damper open an 1"or so. but you need confirmation from them. if you do not have it then get it for both fireplaces.
James