Working With Mineral Wool Batt Insulation

In two jobs of attic floor insulation, and again in the completion of a kitchen remodel in my home, I have made a thorough try of mineral wool batt insulation by Roxul, by the company now called Rockwool, and by Owens Corning, product called Thermafiber.  One experience is summarized in this post. All are collected in blog posts search; Label: Mineral Wool Batts. I am late in preferring mineral wool batts to fiberglass because I work mainly in attics and crawl spaces, where mineral wool has seemed difficult and extravagant. In fact, real momentum in the deployment of mineral wool batts is since the 2013 acquisition of Thermafiber by Owens Corning.


Second Home With Attic Floor Mineral Wool Batt Insulation
This 1918 home has excellent 4 ft wide roof eaves sheltering windows and walls and giving an 18" tall attic perimeter. R49 attic floor insulation out to exterior walls is uniquely possible. Good elevation over exterior walls is an asset to running modern wiring down the exterior walls.

The attic has been barely accessible, dark and dangerous. Despite hostility, the large attic has household items preserved in storage. There is appearance of thick insulation, but many defects reduce effective value to a very poor R5.

After the attic floor has been framed to support an attic ladder,  set a barricade to contain dust and plaster chunks of new attic access cuts conveniently aligned with a stairwell.

The found 2x6 attic floor joists will be strengthened to 2x12, with box beam methods. Build and install a ladder rough opening frame, using select 2x12 lumber. Bahco hand saw cuts through lath and plaster are guided true against the RO frame that is well fit to the ladder frame.

11 1/4" plywood rips serve as box beam webs. Beam top elements are longest-possible 2x4. Everywhere the found loose-fill mineral wool is only 2" deep; found batts draped over that had no value and were in my way. I am happy to reset all found fiberglass batts within the box beams, packed intimately and with much elimination of framing thermal shorts. Found fiberglass batts are progressively shaken free of dust and roof debris upon sheets and into 55 gallon drum liners. Cleaned batts are piled and rationed as base fill within variable spaces below the level of flooring 2x4 nailers. 

I started out knowing only of Rockwool batts, available as R15 and R30, and in unrated 2" thickness. Cut batts 23" wide, to lengths (shorter dimension) accurately fitting framing spaces, using a long commercial bread knife.

18" tall perimeter vertical framing is continuation of exterior walls below, always with closure of cavities in the attic floor (not balloon framing). Hard-covered insulation is 12" thick. I am able to go anywhere in the careful placement of wiring, lighting and new fans, then to be capped with a maximum depth of insulation.

In a final, nicely-accessible zone 54” wide at the North end of the attic, show learned exemplary use of mineral wool batt insulation. I ran out of found wimpy fiberglass I had been recycling for the base layer. At LHS, 2” of loose-fill mineral wool gives intimate bedding on lath and plaster roughness. Over that add R11 kraft-faced batts and R8 mineral wool batts, a total of R21. Crossing Thermafiber R30 batts 24” by 48”, 6” thick, bring the total in 11.5” depth, to true R49.

Over the master bath drywall at RHS, there was no found loose fill. begin with R11 unfaced batts for 1 1/2” fill to tops of on-flat 2x4s found.

Make note of more insulation stack-ups in 2x12 box beam cavities, exemplary of the use of mineral wool batt insulation, rarely disposing found insulation. 

This is typical. I gave up on the use of housewrap strips after nearly hurting myself with kick of a circular saw dividing the plastic housewrap roll. Melted plastic becomes rock. Never again!

Note batt stack-up nearing attic completion, with little remaining found-fiberglass and no raised flooring. Total about R52. What else might one do to achieve serviceable insulation greater than R49? Top-layer R30 batts 24” x 48” are placed, and may be retrieved, from the flooring edge. A covered bath fan and lights will need service someday, then not destroying insulation. The stackup will vary with what materials are at hand, and with needs to fit objects buried. 

This is the Fakro LTK 25/47 attic ladder leading to the completed attic now very energy-efficient, and useful.

Summarize the placement of 1/2" CDX plywood, 22.5 sheets reassembled from 24" rips.

Summarize the attic features.

Summarize the best energy-savings opportunity, closure of attic floor pits. I employ a concept of "equivalent bare area", to collect the savings value of closing air-tight and insulating over the pits.

Here are summary photos of the floor pits as found, and as closed. The opportunities are mostly associated with drop ceilings of closets, now closed or filled full. Energy losses in the floor pits account for most of the math that found insulation was only R5.

Looking Northeast from atop the attic ladder, see an expanse of flat and level flooring. There is easy access to fans and to wiring that is concentrated at the periphery.

From atop the attic ladder, look Southwest past the safety pole, and see all stored items, now easily accessible.

The  full story of work in this attic may be seen in job photo album:
Kabeiseman Attic, June 2018

The story of happiness in finesse work with mineral wool batts, mainly Rockwool now, will go on and on as I continue my work as an exemplary weatherization contractor, age 75 and growing, working always by myself for the experience-to-share. Here are more job albums with employment of mineral wool batts (stone wool):

Coleman Garage Attic, April 2018

Varma Attic, June 2019

Crockett Garage Attic, June 2019

Worthington Attics, January, 2020

I am grateful always for readers, and watch for progress at StatCounter. In this January 2020 update of my post I am inspired by a reader in Japan. I am especially grateful for reader response in comments to a blog post. I will respond to post comments, and I will respond to direct email contact:
pjnorman@gmail.com

To Prep Or Not To Prep

Doing right or not is the question, in contrasting this bid , with the superior work I do. The customer is my sister, who I will love and protect. The bidder is the most successful weatherization contractor in Portland, Oregon, and is allowed, thus encouraged, to do minimum work at maximum cost, by weatherization sponsor, Energy Trust Of Oregon. It is a national problem of counterfeit weatherization under the veneer of grand Home Performance with Energy Star, HPwES. Do a required blower door show, maybe. Deliver blow and go, for little result, at top dollar. Want a useful attic? Forget it. Problems and safe access will be obscured with least-cost blown loose fill.

I hope the reader will care to study poor work offered, but that will make more sense after I describe the work actually done. For now, just know the sponsored bid is perfectly typical of those issued under sponsorship by nonprofit Clean Energy Works Oregon, CEWO, now renamed Enhabit . Now-Enhabit bids with extremely high overhead cost must come to a bid total of about $20,000. If you are an uncooperative home owner, like my sister, the Enhabit bidder will drop you in an instant.

Prep for weatherization, or anything, is not simply doing what is possible. The means must be found, to do thorough, best possible work. Here, access is not initially an issue. It is an unusual 1952 home, Cape-Cod style, where a bedroom is built over a low-ceiling garage. The CEWO bidder called it 1 1/2 stories. I call the opportunity, construction with a loft ceiling, as contrasted with cathedral ceiling. A loft ceiling is not a transition from conditioned space to outdoor conditions with the large energy transition that rots cathedral ceilings; a really good idea. 

Anyone might work in this well-used, lighted attic, so some of the prep is easy. Drop ceilings over the kitchen might be filled, not concealed; yet the CEWO bid missed this opportunity.

Attic walls about the loft bedroom are uninsulated despite concealing mineral wool batts. Many are falling-down. This prep opportunity, to take down batts and provide intimately-fit insulation is also beyond the offering of the CEWO contractor.

Attic contents now fill the loft bedroom over the garage, the nearest move from the attic. And, yet, there are obstacles. Demo the stored plywood. Pull up the shiplap flooring, preserving most of it as treasure to be shared with neighbors. Keep the best, long pieces.

Head bangers are taken-down, to be replaced with roof-peak steel strap ties.

Forty-year old yellow batts look nice, and the CEWO competitor would have left them as-is.

Lift the edge of any of the yellow batts, and see an intolerable mess. The batts are wimpy R13, ancient technology subject to wind washing where not covered, and a health hazard. A foil facing was slashed everywhere although a partial air barrier would have been beneficial. There are voids under the batts where base mineral wool is uneven and spotty. Any insulation simply poured over the yellow batts, as bid by the CEWO contractor, would have no insulating effect, where energy transfer possibilities (natural convection) must drive air flow. There will be much work (prep), in stripping the ratty facing to reuse batts, and for many actions down to the drywall; none in CEWO bid.

This is the untouched condition of mineral wool under the slashed fiberglass batts of the attic floor. Absolutely uneven, much bare drywall, no chance of intimacy with topping fiberglass.

All found wiring will be replaced, with new boxes, devices and LED luminaires.

Wall headers are sealed 100% with flexible grout, as they are revealed.

The central attic floor, within knee wall braces, is raised to 9 1/4" framing depth (2x10), by composite beam method , and this space is used to consume most found mineral wool and all wimpy fiberglass batts, stripped of facing. Needful raising of floor supports for preservation of insulation, strengthening the floor, and restoring useful space, is large work of prep never imagined by the CEWO contractor. 

Complete house rewiring is happening concurrent with insulation work. Most work is outboard of knee walls, conveniently emptied of insulation.

I claim R38 insulation value for cumulative five or six layers of found insulation. Batts are filled proud of the 2x10 framing, to become slightly compressed. The air barrier plywood flooring adds to insulation value, compensating for batt compression. A covered-all-around no-voids condition shall be required of all insulation. 

As flooring is created, move stored items to begin insulation of the floor at the attic entrance.

As further wiring is allowed, modernize power outlets. Always install junction boxes against wood backing. It is OK with my unique opportunity, to offer better methods to electricians.

Long 1x8 shiplap is treasured. Protect it out-of-the-way, until storage space is found.

Work will get easier where there is an excess of floored space.

Some of the composite beam webs are challenged where 2x4 framing is staggered. I readily cope, placing web pieces wherever convenient, about a straight 2x4 nailer path. 

2x4 nailers zigging between plywood web elements yet come out level. The plywood floor will be level and smooth.

I keep moving the needed chop saw station.

Bring in drum liners now, to dispose a dirty layer of cellulose in-the-way, over the bedroom. Disposal is not because of a contained sprinkling of gardening vermiculite. This is a morning activity in high Summer. 

I cut away most bracing at the crawl-in over the bedroom, very needful to make the access bearable.

An 8'x16' space outboard of a knee wall is needed for lumber to be stowed, and more. Build decking elevated over R38 insulation. Know that this framework is built in place, not fitting through knee wall braces.

An uninsulated space about the chimney has been troubling. A person can't fit. The CEWO contractor overlooked it or saw it was too difficult, so don't mention it. I will just do it, fully filling the space with batt insulation using reach poles. It is in the nature of prep, fitting in at a final stage in the insulation of the loft ceiling.

Neat, complete. Tight.

Despite low headroom over the bedroom, raise framing as 2x10.

Before setting insulation and flooring over the bedroom, fill 36" ceiling slopes. Run new wiring.

At last get ready to move out of a 4'x8' space, moving in plywood flooring.

A crawl-upon surface is a lot more valuable than evident headroom. This should be decked, for many reasons.

The attic walls must be largely completed where insulation laces with that atop the bedroom.

Build out 7 1/2" framing for R30 attic wall insulation.

Someday, this attic wall process will be commonplace.

With forethought, there is maximum plywood piece size, and minimum waste.

Composite beam webs raising the supports of attic flooring, are inderrupted or slotted everywhere  wires cross the found floor framing. Where a single batt thickness fills the added height of the composite beam, wires are revealed by lifting only those top-layer batts. This is very important innovation in safe, serviceable household electrical wiring. This practice should be taught to electricians. Use slightly longer wires to run them at the periphery of raised flooring.













The attic is poorly ventilated absent a powered fan. Rebuild the found, dead fan, in a "aperture box." The screen against bugs is of much larger area than the gable louver now not obstructed. I recycled a corroded and crumbling copper screen that had been blocking the louver.

Completion photos, at last. Despite giving up 6" of headroom, the attic is much more useful.

See long lumber stowed over the bedroom. That is a further benefit of the covering of attic floor insulation. See also importance of the covering over the stairwell ceiling. As with skylights, one might else have a very dangerous step-through fall.

Look back before completion, to note some details of the insulation outboard of knee wall braces. In one of the few offers of prep by the CEWO contractor, four soffit vent baffles were offered, surely cheap cardboard. I have my own ways, broadly shared, employing good 1/2" plywood, 2x4 scraps and a few deck screws.

Plan each baffle to accommodate variable meeting of roof and floor joists.




















Know that the Enhabit contractor would have put up cardboard baffles falling-down with small staples, to rot in less than ten years, following Energy Trust Specifications .

Top-layer batts reach all the way to eaves. See little revealed of edge batts 16"x23". At a baffle, place a batt 12"x23", well-stuffed-down. A common edge is achieved for R19 batts 24"x48" in a regular pattern easily rebuilt someday.

The usable volume of a closet off the garage is doubled after demolitions needed for house wiring. The completed better garage closet has 1" combined drywall thickness and a floor of fire rated plywood.

With the complete house rewiring, prep was more than 90% of the job. The wiring was mandatory, starting with a decrepit fuse box and corresponding decrepitude of wires and devices. My way, there was a unique and one-time opportunity to get wiring up to code for the next sixty years. There must be much more mandatory work for electricians, publicly supervised and funded, prerequisite to weatherization. Much post-war wiring is far more dangerous than the knobs and tubes sometimes set in the way of weatherization. Let decrepit roofs and plumbing also be in the way of weatherization, with public solutions. There shall be no deceitful blower-door barons of public action. Damn the actors of Building Performance Institute, still in the way of true weatherization and crucial maintenance of our homes.

In specific weatherization work, prep and the energy savings due to my unique methods, prep is always at least two thirds of the job. The CEWO contractor would have completed criminal fraud in the "prep", the can of foam trick , in an hour. Please read his bid  and see that there is no offer of the gaining of access, to do real prep.

Discounting the exterior wall ruin of blown insulation, furnace replacement and some pretense in the crawl space, all of the CEWO contractor's work would have been done in a day. There would have been no real prep, no honest work done, and my sister's house and finances would have been in ruin. We live on the edge, and fraud can ruin lives.

I will be adding to this in context of challenging weatherization at a national level, soon to participate in debate of proposed changes to the International Energy Conservation Code. My contribution is first in better rules for attic access drop-down ladders, doors and other portals .  There will be debate of lots of rule changes on required house tightness as measured with a blower door. In this, as with hype about attic ladders, there is a lot of misunderstanding, and no comprehension of the math and the meaning of numbers. Some of my thinking in preparation for the code conference is presented in recent update of my post My Home Performance Test . For most houses, tightening against infiltration, at best is effectively the closing of one or two holes 5" diameter, each amounting to reduced infiltration by one ACH50. ACH50 is the number of changes of the air volume in a home in an hour under artificial conditions that of a 20 MPH wind blowing against all outside surfaces. For my home and again suggesting this might be a national average, the ACH50 air flow under natural draft is 7 cfm, perhaps one tenth the flow of a bath fan. Make-up heat to bring that air to 65°F ambient, costs about $10 per year.

The poor understanding of physics and math by blower door practitioners, the CEWO/ Enhabit/ HPwES bidders of my sister's home, is evident in their bid:

Absent a test, they proposed that a blower door would have read 1068 cfm at minus-fifty Pascal test conditions in the home. A number 10.7 air changes, is air changes per hour, at the test conditions. It has nothing to do with the word occupancy. It is an affordable, healthy amount of fresh air, 0.5 ACHnat, changes of house air volume per hour under natural pressure differential. Nothing offered in the bid would have caused reduction of the blower door number in test-out. Any sealing opportunities would be found by sight, long after a test-in, and never guided by the observations in the home under test conditions. 

$2628 would have been stolen. Theft. Fraud. Whatever, it is a commonplace HPwES crime. For all who go along with blower door madness , it is at least a great misunderstanding. I hope I can address this at the code conference, productively.

Absolutely, air sealing is prep, and it is the best investment one can make in weatherization, with quickest repayment, where done at fair cost without the testing scam. Mainly, the sealing in an attic will be of floor pits, with little or no impact on a blower door test. Test-out or none, an existing-home owner will most probably have wished fresh air of about 0.35 ACHnat. Should he have less, he won't be offered expensive mechanical ventilation schemes that might be affordable only in a home under construction.