Thursday, April 10, 2008

Distributing or Hauling-Out Loose-Fill Insulation

55-gallon drum liners are useful for transporting debris and loose-fill insulation in an attic. They may be collapsed as needed to pass through an opening, yet are self-supporting at a thickness of thirty mils.

There are many uses including painting or plaster prep, where major debris is collected on a sheet, and the loaded sheet is easily shaken out in the drum liner.

I buy them from:
CDF, Inc.
77 Industrial Park Rd.
Plymouth, MA 02360

They are 30 mil thickness, Product Code 5530/34.25-G4.
I made a first purchase as a case of ten, with cost and weight breakdown thus:
Containers weighing 39.3 lb, plus box, 45 lb gross.
Charged $118.70 plus $92.91 FedEx freight, $211.61 total.

Cleaning Up A Blown-Cellulose Attic

This attic floor of 2x6 joists on 16" centers had found insulation of a relatively pleasant form of cellulose, up to the tops of joists, R18. The cellulose is compacted to give space for kraft-faced R11 batts. Unfaced R19 batts cross joists to complete an upgrade to about R45. A vapor barrier is acceptable anywhere it will remain securely at temperature above the dew point. It is nice to not place unfaced fiberglass against the cellulose, where picked-up batts would again raise cellulose to the surface.

(Edited at 11/13/2009) The claim of R45 is high. I will call the compressed cellulose R13. Applying my Insulation Math, consider parallel paths for the thickness of 2x6 floor joists.

1/Reff = (1.5/16)/ Rjoists + (14.5/16)/ Rinsulation
where Rjoists is taken as 0.94 per inch (douglas fir), 2.4 for 2x3, 3.3 for 2x4, 5.2 for 2x6, 6.8 for 2x8.
1/Reff = (1.5/16)/ 5.2 + (14.5/16)/ 24. Reff = 18.
Adding R19 batts, total insulation value above the ceiling is R37.

This added exercise tests my installation against a two-thirds rule commonly applied, where less than one third of the total insulation blanket is allowed to the warm side of a vapor retarder. Credit R29 above the kraft facing, R8 below. 29/37 = 0.78. The installation passes the test, but that is not an appropriate end of the thinking.
From a Google search, subject: "vapor barrier two thirds rule"
I have done right for the climate of Portland, Oregon. From study of dew point data for Portland, I have justified a one-half rule. In fact I have never departed from a two thirds rule.

Lacing Insulation to an Attic Hatch Cover

An attic hatch cover of wood or drywall should be insulated in a lightweight frame, not simply by stapling on some twine. The reliefs in this frame permit lacing, and offer finger holds for lifting. Insulation here is high-density R15, in three layers, the bottom having a full-area vapor barrier. A single high-density R38 batt would also do the job.

Duct Wrapping

Here are photos of the application of a duct wrapping material produced by Johns Manville. The material is labeled "Basement Wall Insulation." It has a rating of R11, and is sold as a bulky roll 48 inches by 200 ft. It has a tough white polyethylene and skrim facing. It is best attached with a corresponding white polyethylene and skrim tape in 3 inch width. I expect that corresponding wraps and tapes with foil and skrim facing, similarly pliant, will be associated more with a HVAC unit and its immediate ducting.

The first picture is of a 16" diameter steel ventilation duct. The duct itself has seams and joints sealed with foil tape.

The second picture is of a cabinet set in a home kneewall. The tape of course sticks securely to duct wrap and to itself. It also seems to bond securely to clean wood.