[gorush]

I’m in the process of building a fireplace right now. It is all boxed in ready for the cultured stone application. It has been operable for a while now to insure acceptable operation before rocking it in permanently.

[Tax-chick]

Good idea. You don’t want it to smoke up the house.

[NicknamedBob]

"I’m in the process of building a fireplace right now. It is all boxed in ready for the cultured stone application."

Seeing how well you've done everything else, I'll assume you provided a source of outside air for burning in the fireplace.

A fireplace without such a source of outside air has to consume your nice warm house air and send it up the chimney.