Photovoltaic modules about to be installed on the MCNZH roof
Things are progressing nicely on the Mill Creek NetZero Home. The exterior is almost complete, not including the stucco that will be applied in the spring.
MCNZH - the roof and wire and paper are now finished.
The insulation for the home is almost complete. The insulators put stitching up on the inside face of the walls:
Stapling stitching to the inside face of the walls - the cellulose insulation gets blown in between the exterior plywood and the stitching.
The 16-inch cavities between the interior and exterior walls (the construction is composed of two 2x4 walls, 24" on center studs) were then ready to be filled with cellulose fiber:
One last look at an empty wall cavity. The exterior 2x4 wall (24" on center studs) is on the right, and small pieces of OSB plywood connect the walls. The OSB pieces represent tiny thermal bridges, but with 16" of wood, even the thermal bridges provide R20 insulation.
The insulators then blew the insulation into the wall cavities:
Blowing in cellulose fiber - the filled-in walls have an R56 rating.
Cellulose insulation looks like dryer lint - it's a bit of a messy job to blow it in
The walls now have their vapour barrier:
Mmmmm....cozy warm house-sweater
The ceiling has been drywalled (so that we can spray in insulation):
MCNZH loft, facing north
The loft, facing south. Notice the drain-back tank for the solar hot water system and the sun tunnel passing through.
Finally, we've begun to install PV modules:
Peter Amerongen - a.k.a "The Man" - installing PV modules. There will be 12 190 Watt Sanyo modules and three 4'x8' solar hot water collectors in fixed position on the roof.
Hi Conrad
Love what you are doing here...have been following your build with great interest. One quick question about the blown in cellulose in the walls...did you run into problems getting the drywall to compress the insulation enough?? I ask because I have seen where cellulose insulators staple the stitching or poly not only on the face of the studs, but around both edges a bit, using lots and lots of staples, to keep the insulation from bulging out too much.
Thanks Garth.
did you run into problems getting the drywall to compress the insulation enough?
The webbing (stitching) kept the insulation in place pretty well with about a staple every inch, and it is what kept the insulation in place (not the drywall). It's blown in at three pounds per cubic foot, and that's sufficient force to keep the insulation from moving. At the end of the process, the webbing is billowed (bulging from between the studs). The insulators do reduce the effect by using a big roller. The drywallers do then have to fight the bulging insulation a bit when drilling on the boards.
Just a note, when we did some minor renovations to the outside walls (adding a plugin and precast concrete stair supports), we had to make holes through the walls. The cellulose created a clear cavity when we dug it out (the material above and around did not collapse into the hole) - it has consolidated. They add a starch to the insulation to cause it to bind to itself, which is why cellulose insulation does not settle in the stud cavities. If one were to cut out the drywall, and the mesh barrier, the installed cellulose insulation would not fall out.
I blew weathershield (by thermo-cell) into 2 22.5x48" 2x6 wall cavities behind 6-mil poly. After 2 years I had more than 2" of settling at the top.
I removed the insulation from one of the cavities and weighed it;
14.8lbs which equates to a density of 4.3lbs/cf. Some of that could be moisture absorbed, but the specs state a maximum of 20% water absorption which would still leave 3.6lbs/cf.
If I were going to do cellulose wall insulation again I'd do damp-spray. For my pool addition I'm using fiberglass batts since it is easy to do it yourself.
-Ralph
Mississippi John
Mississippi Mills, Ontario
Hello again Conrad:
I've been meeting with contractors on my deep-wall project, and the issue of insulation application has come up. You noted a bulge after installation:
"The webbing (stitching) kept the insulation in place pretty well with about a staple every inch, and it is what kept the insulation in place (not the drywall). It's blown in at three pounds per cubic foot, and that's sufficient force to keep the insulation from moving. At the end of the process, the webbing is billowed (bulging from between the studs). The insulators do reduce the effect by using a big roller. The drywallers do then have to fight the bulging insulation a bit when drilling on the boards."
My question is, how much hassle was it for the drywallers to apply the boards given this buldge, and have you noticed any "popping" of drywall in the 18 months since??
One local contractor I've spoken to suggests this could be avoided by strapping the walls after and apply the drywall to the strapping - similar to how you do it on the ceiling. But if your experience is minimal hassle for the drywallers, perhaps this additional cost could be eliminated.
Thanks again for your most excellent site.
John
Hi John,
We've had some screw popping, but not that much (maybe 10 screws?). I know that it happens on a conventional house too, and I'm not sure if we had more screw popping, or a normal amount.
My builder said that the drywallers grumbled a bit about it, but as far as I know, no extra cost (in time or otherwise) was incurred.
Conrad
I know it has more embodied energy than cellulose, but for our deep wall project, we'll be using JM Spider, which is a blown fiberglass with a bit of glue mixed in so it stays in the wall cavity without any webbing, and has a bit higher R value per inch with similar airflow resistance.
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