framing for cellulose in the walls

As you may know from reading some of our previous posts, we are pretty into using the SIP wall building system for it's excellent r-value performance, greatly reduced thermal bridging & air infiltration issues--- as well as the relative ease and speed it facilitates when we're " framing the walls". But it's not always the best choice for a client.- For a variety of reasons including clients that want to use "all natual materials" we sometimes end up using an altrante 2x6 framing method instead of the SIPS. This alternate framing approach means we have to work a lot harder to achieve the same high r-values and energy saving performance in our walls. We recently applied this approach to a house in the White Hawk co-housing community in Danby New york. Here's how it all went together.

FRAMING: Once we had the exterior walls framed up with typical 2x6 stock 16 inches on center, we added a 2"x2" strap horizontally, 2 foot on center to the out side of the walls. Having done that, The exterior was ready to be sheathed with OSB. With that all done, we were then able to seal all the seams and edges of the exterior walls with expanding foam, and finally apply our wind wrap (tyvec) to the outside of the house. ON this particular house the final siding was to be locally milled, rough cut board and bat Hemlock.

INSULATION: During this work the air temps were hovering in the mid teens ...yes 15-20 degrees below freezing. Spaying wet stick cellulose was not an option. Instead we attached a breathable but not streachable fabric product called Insulweb to the inside of the framed walls (to support the insulation) stapled it heavily to the studs and cut a 5" or so slit cross about 12"-18" from the ceiling, and at around 36" from the floor in each stud bay. These access holes allowed us to easily blow dry cellulose into the wall cavities until they were full- and firm when pushed against with by hand. The insulweb fabric does tend to bulge out a bit as the wall are filled and that can be a problem for drywallers, so using 5/8" drywall board is strongly recommended. When it was all said and done we had a minumum of an R-26, 7" dense packed cellulose wall, with greatly reduced thermal bridging and the added benefit for these clients of reduced use of petroleum products- and we all can feel good about supporting a green product like recycled cellulose insulation!