Blown Wall Insulation

Attached is a graphic showing exterior blown cellulose wall insulation in a 1900s balloon wall framing with defects such as unfilled voids and insulation settlement. I don’t have any current infrared pics to show this, but the voids and settlement are easy to spot. The 2nd photo is not mine, but on balloon framing this insulation typically falls out onto the sill plate. (I flipped the wall around and removed the flooring to see the insulation goes to the sill plate.)


Before my wife and I were married, some new insulation contractor blew cellulose into her balloon framed house and didn’t understand why it took so much insulation.

The crawlspace part of the house was almost full of insulation and were his guys pissed that they had to dig it out and plug the bottom plate area and fill the walls up again. :crazy_face:


Thanks, Randy. :slight_smile:


whoa. can they turn the blower machines in reverse and vacuum it up? I imagine that’s how its normally removed from houses, right?

No not the same machine.

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Marcel is correct…not the same machine and since it was very new company the didn’t have that machine yet.


Consider adding both fireblocking and diagonal bracing inside the stud cavities.

The missed voids are often above or below a fire block.

Or, above or below a diagonal interior brace, of the type common prior to the plywood era and used after that still occasionally. Such diagonals leave a triangular area without insulation. The installers must probe each hole to determine the cavity depth, to find the fireblocks.

Holes for blow in on the outside should show a detail of how the WRB is punctured.

Holes for blow in on the inside don’t share that problem.

Here’s a photo I took yesterday of cellulose insulation at the base of a gas wall furnace:

This is a house I am helping rewire, a fire job. Built in 1883. Balloon framing, insulated probably mid century. No weather resistant barrier, siding is installed directly on studs. You can see the plugs where insulation was installed. Oddly, they didn’t insulate the upstairs or it settled that much.

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