Insulation Preparation

The exterior walls are 12" thick.  The inner 2x4 studs are filled with Light Straw Clay (LSC), and the remainder of the 12" will be filled with blown-in cellulose insulation.  Lowes makes it easy: buy 20 bales of Green fiber insulation, and you get free use of their blower.  Like most tasks, there is a fair bit of preparation that needed to happen in order to streamline the process.

Most notably, the light straw clay only extends up to the bottom of the I-Joists that form the ceiling, so I needed to add blocking to seal off the cavity at the ends of the beams.

I nailed plywood panels in using wooden cleats, top and bottom.  To avoid having to measure precisely, I just left about 1/8" clearance all around and caulked them tight.  That took care of the north and south walls.

The east and west walls were easier, since I could just nail up luan plywood strips to the studs (that's the reddish strip on the left of the photo).  The 1x2 straps below the luan will support the drop-in ceiling panels, and they do double duty by giving a clean line for the luan to butt up against.  

For the most part, the stud cavities were filled from the outside via holes in the exterior sheathing.  The one exception was that the areas under the windows were more easily accessed from above.  I bought a GreenFiber Nozzle to reduce the 2 1/2" hose that comes with the blower to 1".  They even sell plastic plugs that make it super easy to plug the 1" holes.   Those are the white circles, with the window on the left of the photo and the 2x4 LSC inner wall on the right. 

I supplemented the GreenFiber nozzle nozzle to help me control the direction of the cellulose as it is blown in.  All I did was cut off the last 3" of the nozzle (after filling in under the windows) and duct tape it to a 1 1/4" diameter long-sweep 90 degree electrical conduit elbow.

I had to determine how far below the top plate of the walls to locate my 2" diameter hole so that the nozzle would point up above the Light Straw Clay.  The magic number was 7 inches to the center of the hole. 

This allows me to blow up to fill in the area between the I-joists and behind the blocking I described above. 

 It's also desirable to point down and towards the plywood.  Since the LSC can be rough, I prefer that jet of insulation to hit the smoother plywood since the straw might tend to catch the insulation and leave gaps below.

It was a hectic day when it came time to buy the insulation and haul it along with the blower machine to the house!  For better or worse, I don't have any photos or videos of that process since we were pressed for time.  More on that in the next installment,.