As a Trade Ally of Energy Trust of Oregon, banished for protest, I yet attend Trade Ally Meetings, most recently that on February 21, 2012. At this meeting, I mostly just listened in. At the end, I spoke up against ridiculous coping with can lights.
Listening in, I was surprised to hear that air sealing of an attic floor is not required if joists are not visible above insulation. This was expressed as if it were long-standing established policy. Back home, I looked up the words in a draft revision of Specifications for 2012. The changed text in each year's revisions is highlighted.
The new blessing of crime is at page 17, AT 1.1 - Attic Air Sealing
*Top plates may be considered inaccessible when covered by more than five inches of loose-fill insulation or covered by a combination of batt-type and loose-fill insulation. Exterior top plates may be considered inaccessible if adjacent to eaves with a 8/12 or lower roof pitch. Batt-type insulation alone shall not be considered a barrier to access. (highlighted)
This is a specific give-away that allows loose-fill blow-and-go jerks, to stay in the business of just blowing and going. In the typical attic floor with 2x6@16 framing, with found R19 loose-fill to be supplemented, the settled insulation will be nearly 5" deep, with 1/4" covering of joist tops. The exclusion will be claimed and defended. There will be no diligence. No uncovering of savings opportunities to likely have five times the value of added insulation. Those savings then hopelessly lost in the deep sea of loose-fill, that will fall from an attic in any traffic, tracked by any tread in shoes, value damaged irreversibly by the traffic.
Cellulose, and even mineral wool, are fine as base insulation, below joist level, covered then in upgrade, by batts and decking. Here is an example of what is possible, if we stop encouraging the slackers.
At September 2012, I see that the offending exemption of sealing has been deleted in the issued Specifications:
AT 1.1—Attic Air Sealing
To prevent transmission of water vapor and to support the effective R-value of the attic insulation, Existing Homes recommends that all accessible attic penetrations are sealed. Attic air sealing opportunities include plumbing, wiring and duct penetrations, top plates, mechanical chases, soffits and similar openings in the air barrier of the attic. If air sealing, appropriate backing materials shall be used to bridge openings that cannot be effectively closed by a sealant. Caulk, foam or other compatible sealants shall be used. Target areas are listed below in Tables AT 1.1a and AT 1.1b. See the Air Sealing section in this manual for specifications.
Sealing is merely recommended. That is not any better than forgiving it, to those lacking conscience to do right. Dishonest conduct, obstructing the most important work of weatherization, will go on, approved.