First, great forum! Kudos to all who share their time and knowledge.

I have a 25 y/o masonry fireplace with the face brick removed. A Level II inspection with camera revealed the smoke chamber was not parged at construction. Current brick thickness at top of breast plate is approx. 4"- one brick thick. It thickens as you move up the smoke chamber (corbelling)to at least 9" thick at the top of the chamber.

Sweep recommends parging with a certain UL listed refractory mortar that allows combustable contact with 1.5" of product and 4" of brick (not sure if I can post product name.) This would bring the current masonry fireplace up to code and allow installation of sheetrock above the mantel (in lieu of the original floor to ceiling brick), but I'm still left with a drafty, inefficient fireplace.

Is a properly installed direct vent gas insert completely self contained? That is to say, do any fireplace gasses/ smoke fill the smoke chamber or flue?

How much heat do these units generate in the firebox/smoke chamber/flue? I'm looking at whether the heat generated from the insert could heat the brick on the inside enough to cause problems with combustables abovethe mantel. A retail hearth store told me the firebox of an insert is cool enough to touch- the flue is too hot to touch (though not hot enough to scorch), and the front is very hot, but the back, sides, and top do not conduct significant heat. Is this true?

If negligible heat is generated outside the box, and no gasses or smoke escape it would seem this is a good alternative to parging the smoke chamber.

Thoughts?

Thanks in advance!