what is best way to insulate exterior chimney?

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John Ackerly

Burning Hunk
I'm about to install a Woodstock Soapstone stove in front of my fireplace and wondering what is best way to insulate the inside of the fireplace so heat isn't lost to outside. Up until now, I've had stoves tucked into the fireplace, and I can feel the heat radiating right through the brick to the exterior of the fireplace, since its on the outside of the house. Would sheets of Durock be a good solution to fit behind the stove, against the walls of the fireplace? Or big pieces of slate? I need to get to the back of the stove so can't seal up the front of the fireplace altogether.
 
I have enough room in mine that I'm putting in 3 inches of roxul insulation with durock on top. In the process of doing it now. Durock by itself might help if you leave a space between it and the walls of the firebox.
 
Whatever you do, you must have an air space before the fireplace. You could, if there is room, simply dry stack bricks between the stove and the fireplace.
You have brought up one of the big problems with most fireplaces, they are built on an exterior wall, and the cold outside is transmitted right through the masonry and into the house.
My fireplace is entirely within the house, and any heat generated into the firebox walls is emitted, slowly, back into the house, and no cold outside air ever hits the fireplace.
 
Roxul comfortboard or micore are good insulators, but a couple layers of durock nex gen are better than nothing
 
Like begreen said roxul micore or ceramic wool would be best brick wont do much at all they have very little r value. I just saw lowes is now carrying roxul rigid board insulation that looks like a good product for situations like this
 
I would build a moveable false wall out of non-combustibles, maybe steel framing with durock attached to it, it would come apart in half. Your horizontal 6" liner would go through it in the middle, so when you need to get to the back (how often is that?) or you need to clean the liner you could take the false wall down easily.
 
saw it online i will try to find it again quick
 
You have brought up one of the big problems with most fireplaces, they are built on an exterior wall, and the cold outside is transmitted right through the masonry and into the house.

That's exactly what convinced me to install a second stove in my second fireplace. The second fireplace is on an exterior wall, and during a cold snap the rear brick wall measured about 30 F. That room was always freezing.
 
They also sell it at Home Depot. Looks like you might be able to buy it by the sheet or get a pack of 6 for around $50. I'll give it a try and post a photo. I want the false wall just half way back in the fireplace.
 
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