Wednesday, November 19, 2008

Coping With Attic Vermiculite

In December, 2006, I added batt insulation in this attic, grading vermiculite to a uniform distribution, while wearing a respirator. I would do better now, with advice from a competent testing laboratory, and mindful of US Government advice at:

Without negative confirmation, it should be presumed that vermiculite and many other construction materials have small asbestos content. Testing to a negative for vermiculite is expensive in the current method, with three gallons of material, taken in one gallon complete cross sections.  If an installation is positive for asbestos, mitigation is expensive, perhaps $10,000 in this very large attic. After mitigation, by a licensed abatement contractor, I would still not bet on absence of asbestos. Who knows where particles might have settled, to be stirred up by intrusive action such as drilling for wiring placement. I would rather be warned by visible vermiculite, to take protective measures.

The protective measures include careful wearing of a HEPA-filtered respirator, with appropriate control of respirator elements and clothing. 

In an attic floor, vermiculite adds to step-through safety concerns, adding justification of lighting and safety decking. 

Saturday, August 16, 2008

R30 Crawl Space Plan, 48" Joist Spacing

Please double-click, for a somewhat larger image. This is an installation I will be trying in the next several weeks. I post this for comment, especially from Energy Trust. Is there a simpler way of doing this? Don't we agree insulation and support means should not hang down, with danger to the installation, and obstruction of passage? Certainly, infrequent supports must not permit insulation to fall out of contact with floor sheathing. Most crawl spaces do not have an excess of headroom.

Wednesday, July 30, 2008

R30 Crawl Space Insulation, Materials Choices

In Oregon at 2008, weatherization sponsor Energy Trust  requires R30 for crawl space insulation. For floor framing of 2x8 at 16" on center, the available Johns Manville batts are 16" by 48." This photo shows placement of a kraft-faced batt within 2x10 joists. Although free-standing batts are 10.25" thickness, batts stably compress to less than the 7.25" joist depth. Side compression and friction give sustantial retentive force. The batt is forced against floor sheathing, and is fluffed down to just fill the cavity. R30 Cathedral (high density) batts are inferior in this application. Contractors who place twine to hold up batts are misguided and do a disservice. I blame irresponsible advice of Bonneville Power Administration for much wasteful placement of floor insulation. BPA calls for R19 batts resting on twine or wire, making tempting habitat for critters, until the insulation falls down, and having no insulating effect. Twine will do nothing to force floor contact of a batt R30 or less in 2x8 framing, even at 16" oc. An R38 batt might be retained in floor contact, but not with joist spacing more than 16" oc.

Requirements do not specify whether batts should be kraft-faced or unfaced. I will choose kraft-faced, with belief that flooring often contributes to house infiltration. Foundation vents, even with typically-crummy plugs, leave the crawl space as the entry point for the chimney effect of air circulation. The kraft facing will be an imperfect barrier, but may help. Wouldn't we do more good where the crawl space is substantially open to outside air, to run house wrap under the insulation?

I have tried both R30 and R38 Cathedral, high density batts. For appearance and security of fit, I prefer the R38c, to ordinary-density R30, but find the added cost not justified. The R38c better fit is in part from manufacture at 15.5" width. I wish there were more choices of width for R30 batts.

This illustration for floor framing of 4x8 on 48" centers expresses a dilemma. Whether kraft faced or unfaced, R30 batts are available to me at only 16" and 24" width. I want batts to be retained without billowing down below the joists, because space is often limited, and slack batts are at risk of destruction by a challenged, snagging worker. Insulation must somehow be kept in intimate contact with floor sheathing, everywhere; billowing batts with slack wire or twine, must not be allowed. But, what of the batt interference illustrated, where batts are tried without any custom sawing?

At 9/13/2012, note that better information can be maintained on a web page. Here are pages for several joist configurations:
4x6 At 32" On Center 
4x8 At 48" On Center 
2x8 At 16" On Center 

At 5/2/2016, consider this proposal submitted for 2018 revision of the International Energy Conservation Code:

Revise Table R402.1.2 Footnote g, and apply it for all climate zones.

g. Floor insulation shall be in full contact with overhead sheathing and shall be retained by an underside air barrier. If the air barrier is set against joist bottom faces, bays must be over-filled, generally compressed to much less than batt free thickness. An excess of insulation, more than label R30, shall be required for common 7.25" joist depths if batts and air barrier material are not raised to make contact with the subfloor, above joist bottom faces. Where a crawl space or unconditioned basement does not follow outdoor temperature extremes, with outdoor vents safely, easily and assuredly closed during colder weather, air barrier-faced batts shall achieve floor R-value 19 in any climate zone . 

My code suggestion derives in part from success with hard-covering of insulation in a crawl space overhead for immunity to mice and rats: 

The proposal needs substantial revision to look like "code."

The outcome of passage might be be manufacturer offering of fibrous, compliant insulation material bonded to OSB in useful sizes including 43" width for the difficult 4x8@48 situation. Perhaps a standard R19 or so, for any climate zone with CS not vented in extreme Winter.

In the matters of climate zone and practices of winter closure of vents of an unconditioned crawl space, note that venting for radon is a seasonal concern. My home in Climate Zone 4 with vents closed experiences radon levels above 4 picocuries per liter only in wet spring weather with ground water-saturated and is well below action levels in other seasons. I am getting to know how my crawl space behaves while devising the means to condition it as unvented year-round.

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.