To bud in it has been a while since I have seen a fireplace, but the direct vent ones, through the wall that I remember were all standing pilot, and I do not remember the glass being cold to the touch so I would not worry about it.
Maybe if something had a taller vertical vent that was coaxial, it would work like a hoyme HRV. Cold air falling in the annulus would get heated up by air rising up the vent.
Perhaps hearthman will have the answer, otherwise measure the glass temp on one next winter and let us know.