Blocking open joist cavities found in balloon construction

[SIM]

In balloon construction there is no top plate and the floor joist cavities are nailed directly to the wall studs. As a result, the joist and wall cavities are continuous. When dense packing the exterior walls with cellulose insulation you must first block the opening to the floor joist cavity or insulation will continually flow between the floors.

This can be accomplished using a long bag that gets filled with cellulose, if access is available, or smaller bags that are filled in the individual area created by each joist cavity.

[goingreen]

After watching the video I understand what I am looking at here. You not only have joist cavities (above and below) but they are open to a gap between the floor and ceiling joists. What I don't understand is why the house was built with this additional space instead of having one set of joists serve as both the floor and ceiling? Is this common in balloon construction? What's the point?

[dmitrimartin]

Where did you find these "onion bags". I've been using 3 mil plastic bags but have to turn down the blower pressure or they blow out every time. Unfortunately, the low blower pressure often causes my hose to plug up.

[SIM]

Those are custom made onion bags and they were provided during a training session with Wisconsin's Focus on Energy program. I don't know anyone that sells them.

A possible solution is to use an old pillow case or if you have a bunch of band joist cavities to block you can make them pretty quick out of old sets or table cloths.

Do you pop some holes in the bags so the air can escape? That sure is a simple fix if you can let there air out but keep the cellulose in.