chimney insert wall

[wes owens]

I found this on a new construction.

The chimney insert wall in the attic only consisted of 2x4 bracing and no wall.
The B vent pipe ran up and out of the wall into the attic and through the roof.

The batt insulation was just standing in between the studs, and the blown insulation was around the pipe down in the wall at the fireplace.

Shouldn't there be a wall on the back side of this chimney insert?

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[Frank Kunselman]

The lack of draftstopping/fireblocking is the least of your concern. Yes the chase should have been a closed chase or at least a lid at the ceiling level.

However, if it had been there you would not have found the other problems such as the lack of required clearance from combustibles for the B-vent. Also the blown insulation on the firebox is a fire hazard, both from code standpoint as well as mfg instruction. The insulation in the wall should have been unfaced as the kraft paper will smolder and scorch.

Then there is a question on the vent sizing itself. Is this a "gas log" unit...looks a little shallow from the pic to be a real wood burner? The chimney vent would be too small if the unit is a wood burner.

Sheathing the attic side would generally be acceptable with the proper thimble on the vent at penetration. However there a lot of corrections to be made before recommending closing it up.

[Bob Harper]

The fireplace must have a listed firestop in fireblocking at each ceiling level. The insulation must be sheathed over just like any other exterior wall and yes, that Kraft paper must be sheathed over or otherwise protected from ignition sources such as the fireplace. The stated clearances must be met around the fireplace. The blown down insulation must be removed. The elbow and horizontal run must be supported per mfrs. instructions.

This appears to be a little Bvent factory built fireplace--not an insert. Inserts are 'inserted' into exisiting fireplaces. From the physical size and 4" B-vent, I would guess it is rated for less than ~ 22,000 BTU/ hr. input. The fact there is so much wasted room is not a problem per se. In fact, it allows a retailer to yank that unit and install a large one at a later date.

Why in the world did they exit the chase and enter the attic with the vent? Nice job of hacking huge holes in that gable wall, though I don't understand why it is insulated up in the attic.

This installation does not comply with the Fp mfr., B-vent mfr, or building codes.

hth,
Bob

[wes owens]

Thanks guys.