frost on natural gas fireplace insert

[tenax]

in the past week, i replaced the tile surround that went around my ngas fireplace with a eldorado stone surround..the ngas fireplace was installed in 2004 into an existing zero clearance fireplace space. while i've noticed cold air before coming in around the ngas fireplace, i never noticed nearly as much as i have coming in now and i've never had frost on my fireplace. i'm not sure if it's because i

a) don't currently have the pilot going on the ngas fireplace which usually keeps the fireplace quite warm
b) because i brought in the edges of the eldorado stone much closer into the edges of the ngas fireplace frame so the cold air is concentrated through a smaller space
c) a combination of both of the above.

i haven't fired up my fireplace pilot as i have to clean up the frame and glass at this point from my stone surround build still and i thought i might bake the guck on at this point.

so, let's assume that running the pilot takes care of the frost issue and the cold air coming in gets warmed up, i feel it's still very drafty..it's a direct vent fireplace so if i were able to seal it off more to limit the cold air coming in the edges, i think that would be a good thing? i was thinking a place to start might be some kind of gasket that won't melt or burn that sticks to the frame that the ngas insert backs onto. the weight of the insert would help seal the fireplace somewhat? i also was thinking of dropping batt insulation into the cavity behind the ngas fireplace insert..i know that won't help drafts but thinking it would at least create a barrier so the space doesn't get so cold. any thoughts on those ideas..or any other ideas?

edit- here's a product i came across that sounds like it would be helpful maybe?

(broken link removed)

 

[tenax]

well, for anyone else who might run into this who is interested, once i fired up the ngas fireplace pilot, i had no issues with frost last night. my theory is that the cold air is warmed by pilot light heat as rises up the chimney mixing with or pushing back the cold air (it's hot enough to make part of the glass too heat to touch soooo...) but, it still underlines how drafty it is and i do intend to see if i can buy a gasket to help block the draft somewhat.

 

[DAKSY]

so, let's assume that running the pilot takes care of the frost issue and the cold air coming in gets warmed up, i feel it's still very drafty..it's a direct vent fireplace so if i were able to seal it off more to limit the cold air coming in the edges, i think that would be a good thing? i was thinking a place to start might be some kind of gasket that won't melt or burn that sticks to the frame that the ngas insert backs onto. the weight of the insert would help seal the fireplace somewhat? i also was thinking of dropping batt insulation into the cavity behind the ngas fireplace insert..i know that won't help drafts but thinking it would at least create a barrier so the space doesn't get so cold. any thoughts on those ideas..or any other ideas?

How is your unit installed?
Is it in a bumped out enclosure (doghouse), or is it an internal install?
If it's in the doghouse, & that structure is cantilevered over your foundation,
you've got an inherently cold install & have to seal the inside of the enclosure
BEFORE you install the box to eliminate any drafts from cold air penetration.
It sounds like you're a little too late to do that - unless you tear the siding off the
house & try to seal everything from the outside.
You can also try using aluminum tape to block off EVERY seam & hole
in the compartment underneath the firebox...
You've got gas line & wiring coming in & some units have relatively large holes for
access/install of these items...
Another problem with doghouse installs is the simple fact of natural air convection...
Warm air in the room will come into contact with the colder metal of the firebox &
the air will drop - as it cools - thru the same cavity where the blower would move
room air to get warmed - creating the illusion of a "cold draft" coming out
of the bottom of the fireplace...
Sometimes leaving the pilot on can minimize this effect...
We used to install units & leave a couple of 4" holes thru the deck & into the joist space &
cut holes thru the joist bridging to allow for SOME warm air movement into the doghouse,
but local building/fire codes put the kibosh on that & made us seal em...