Please consider virtue in the accurate and strong build-out of 2x4 to 2x6 thickness in this exterior wall section of my 1955 home in Portland, Oregon. Here is that build-out immediately upon demolition of the wall formerly separating the kitchen from an on-foundation concrete back porch. Found 2x4 framing in this exterior wall is strongly thickened to 2x6. New outside wall framing is 2x6.
And here is this kitchen in a nearly-complete condition, September, 2018. Added depth of exterior walls was important too, to better framing of windows and a door, and simplified plumbing and wiring.
I had despised drop-ceiling headers over kitchen cabinets. Such headers are awful heat bleeds in most homes, where at exterior walls they are not accessible for insulation. Too often, none of the headers are filled with insulation. I have the opportunity to expand my kitchen 40% with modest effort where the little kitchen exited to the back yard via a concrete porch fully on-foundation.
It was a crummy little kitchen, and held down the usefulness of the house, beyond being the last room in my house where I had not demolished interior drywall to accomplish data and power wiring improvements, plumbing replacements and tight R15 insulation.
In this one room I would accomplish R22 wall insulation in 2x6 framing.
The improvements are a lot for an individual to accomplish, and are still in progress. For now, share just the details of a 2x4 wall built out to 2x6 with innovation important to progress in existing home energy efficiency and in preservation of well-built homes of the 1950s, defending against demolition.
See my build-out to 2x6 thickness of an existing 2x4 wall. At top place an on-flat 2x4 and 1/2” plywood rip. Stitch on lengths of 5” rips of 1/2” plywood as composite beam webs. Place 2x2s true vertical and flat, leaving 1/2” thermal breaks of both the 2x framing and the webs. The 1/2” gaps behind 2x2s enable simple running of wires, without steel plates to mess up drywall flatness.
Fit 2x6 extensions of the wall bottom plate, and set screws to align the 2x2s flat and vertical. The 1 1/2" raising of nailers for drywall and baseboards, is very useful.
No! There is a better way.
Serious about this in late Summer 2017, I have reset the wall build-out to employ an upright 2x4 at the floor, for better baseboard attachment opportunity, and insulation a bit better.
I will have a much better kitchen, in a home that inspires possibilities with solidly-built homes of the 1950s. Details here are near-final. I do all work except cabinetry fabrication.
While exposed, the built-out framing was a laboratory of insulation methods, sharing photos in conversation with Insulation Institute . I started out with an exceptional exterior wall judged to be R_total = 5, U = 0.2 not counting added value of wall joists and to-be-added insulation batts. To a generally-applicable R3 value of airtight sheating inside and outside, add R2 value of Celotex sheathing . Exterior air tightness is achieved both at well-set old-growth cedar siding, and at overlap of Celotex edges. Start with less than half the conductivity and heating cost of common, cheap, non air-tight construction, Rtotal = 2.5, U = 0.4.
Walls built this way are to be treasured and preserved. I'm not sure what should be done with more-ancient walls, hopelessly leaky, hollow, cobweb strewn, with structural defects and dangerous wiring, ruined of insulation value. I suspect though that salvageable homes are determinant not by age, but by investment at time of construction.
Where is the pride of any employee or contractor of the US Department Of Energy paid to support residential energy efficiency, when USDOE Home Energy Scores treat all exterior walls without some insulation stuffing, as of paper, R_total = 0.4, U = 2.5 ? This perhaps-deliberately fuels older-home demolition regardless of solid construction. This is applied for all insulation opportunities, exterior walls, ceilings and floors. It encourages false claim that very-huge energy savings can be achieved by a blow-and-go scammer foolishly just adding some partial insulation atop wiring, plumbing and structural messes, if the home is not demolished.
The subjects with Insulation Institute have been layering of batts to kill framing thermal shorts, full batt containment to avoid air circulation, and lack of value where insulation does not fully fill available space.
I wait, and wait, for recall of misinformation in this NAIMA instructional video of year-2012 . I bought and here tested a bag of the yellow Certainteed R13 insulation placed by the championed installer. Please watch the video, and see that the installer takes great care to not press edges beyond joist faces. I just don't know how to do that, making a fluffy batt 3" thick look like it fills the cavity space, as it must. It seems that alone among insulation manufacturers, Rockwool (formerly Roxul) , makes batts specified for a framing depth, that reliably fill the space. Look closely at the beginning of the video to glimpse Rockwool as exemplary insulation.
In my 2x4 garage wall, here is a length of Certainteed unfaced insulation wrongly rated as R13 in a 2x4 wall. It has been placed here for more than a year, in incomplete communication with NAIMA, North American Insulation Manufacturers Association. At 2016 hearings for revisions to 2015 International Energy Conservation Code, NAIMA defended code-allowed underfill of framing, defeating my proposed requirement of full filling always, by overfill that accommodates small-batt tolerances
In fact, R13 batts NEVER fill 2x4 framing. Where gaps will exist all around a batt, then with low flow resistance for air. Air circulation, driven by energy convection and outside wind pressures, may reduce insulation value to zero. There is no reason this should be allowed.
At last rounding this corner with drywall, I apply last-minute grouting of a vent annulus, with my always-available flexible grout. See that Rockwool R15 insulation thoroughly fills the space, accurately cutting to width from 23"x 93" batts. Do the math on cost of this Rockwool vs. the experimental Certainteed R13 with no value, for one 16" oc frame bay, batt area 14.5*92/144 = 9.3 sq ft. The Rockwool cost $649 per 1000 sf. The R13 cost $397 per 1000 sf. The one batt cost, 9.3 sq ft, is $6, vs. $3.70. Proper code must keep a silly person from pocketing the negligible difference in installed cost. A DIY home owner must never be tempted to do wrong in a cheaper choice, by believing a "For 2x4 Framing" label on a crummy R13 bag.
I think insulation installers wrongly do not expect to find a family of batts that in layers, add up to fill the space, giving promised R-value. AFB batts about R8 are not sold as suited for layering with object sandwiching. 2x6 walls may be filled with R23 Rockwool batts, or when necessary, with layered AFB: R8 and R15. 2x4 walls may be filled just-barely, with R15 Rockwool batts, or when necessary, and perhaps better always, with two layers of AFB. Layering of manufactured consistent batts to deal with odd cavities, is not just good practice. Rockwool batts do not part, and hacked cuts make a big mess of a job, with puzzle pieces that challenge patience and result in deficient R-value.
In new 2x6 walls, begin with AFB batts. there is certain ability to stuff an inch of effective insulation behind a crossbar that allows outlet placement distant from a 2x6 joist.
Here again see my trusty commercial bread-cutting knife, used for all cutting of batts. Cutting in and around friable Rockwool batts is easier and more precise than in stranded fiberglass batts. Where we admire honest, uniform thickness and easy shaping of Rockwool batts, also celebrate discarding of ill-conceived kraft facing as a leaky, crummy "vapor barrier."
We need combinations of mineral wool batts that may sandwich wiring, as parting is just too awful. One R15 batt and one AFB batt, or one R23 batt. nicely fill a 2x6 space. Doubled AFB batts as sandwiching in a 2x4 wall have excessive overfill. One needs many screws to pull in the drywall with compression.
Overfill is not the goal. Overfill is demanded only where batts have unreliable thickness, to get complete fill always.
With full demolition of drywall at the garage 2x4 wall, see dripped flexible grout from wall header sealing in the attic long ago. Plaster the gap now.
Seal the wall header fully.
For good reason and as demonstration of good example, buy a new coil of Resource Conservation Technology BG32 EPDM gasket.
The BG32 gasket consumed here will cost me less than $6. With flexible grout sealing of existing drywall, it will block a leakage path to the attic that is poorly accessible, and was not sealed before.
At the somewhat conditioned garage wall, insulate with R15 and layered-R8 Rockwool.
Finish GP Densarmor drywall pieced-in, using flexible grout and Structolite plaster, over joints well stitched with screws and backing lumber. Set joint paper tape in 24" lengths, at ceiling and wall corners only.
Date: 2/23/2018. Ideal condition for wall observation with an infrared camera. And, I don't own one. A camera investment of about $10,000 can have no economic return to me. I leave no voids, always maximizing insulation value. I believe there was nothing more to do, to improve comfort and reduce operating costs at these exterior walls. I have at least the R23 before-framing-allowance achievable in 2x6 framing, with tight mineral wool batts. The modified 2x4 wall is yet-better insulated. And, ask now, by how much, and how much some defensible difference, matters. Least-rigorous math has 1/Reff = 0.25/5.2 + 0.75/23, Reff = 12.4 for simple 2x6 walls with 25% framing factor, R23 batts. Use Insulation Math for this home, Annual cost of heat = $2.4*Area*U. U = 1/(R + 3), Wall area 250 sq ft, Annual cost of heat = $39. If I could somehow have R23 framing, the annual cost of heat would be $23. I'm being glib about window and door much larger heat losses accepted as imperative. Have I done something wrong to accept $16 per year unavoidable heat loss for walls in this room?
I will not be shamed by extremes in this current blog post of Insulation Institute:
3/21/2019, Mineral Wool: A Solution to Thermal Bridging
See what they might have me do as exemplary use of mineral wool batts:
I see wasteful failure to fill 2x6 framing space. I see exterior insulation that can't be part of sensible and strong construction. I see failure to be realistic about thicknesses and labeling of on-offer batts, 2" R8, 3.5" R15, 5.5" R22, 7" R30. There are no 3" batts. There is no acknowledgement that mineral wool batts can't be parted to go around wires or pipes. Then offer layering, for example:. 2" + 3.5" = 5.5", ~R22.