Insulating A Roof

Who says it is OK to foam a roof, for any odd contractor or home owner? We should fear roof rot within twenty years, unless foaming is with perfect completeness and perfect maintenance, forever, of a vapor barrier over the expanded living space. No one can offer that guarantee. A roof, foamed, rotted, is ruined. 

Instead, Raise The Roof. Look for agreement with the statement "raising a roof does better weatherization than insulating the roof ." Practically, it is less a quest to save energy if a bungalow attic has been converted to living space, and is uninhabitable especially in Summer. Claim comfortable living space, and more of it.

Raise a roof, Then weatherize an ordinary attic . Be smart though, about second floor spaces outboard of new and existing attic walls. The excellent builder here sealed none of the large openings between not-conditioned floors, and the walls and ceilings below. Whimsical bungalows will remain challenging of weatherization. Simple cape construction has much hope of rewarding and fairly easy cures, in modified roofs.

As a weatherization contractor working alone, and not as manager of a crew, I have insulated a roof, only a few times. Foaming a roof is not an option, in my opinion. The task with batts is a serious one and will usually be only-wishful thinking of a home owner. As growth of weatherization activity it is not likely in one's budget.

I want to illustrate my general approach, and immediately think of this example of a nice home in the prosperous Irvington neighborhood of Portland, Oregon. The link is a Google Photos album.

This afterthought child's play room in a kneewall closet, was cozy only a few months each year. It was mostly uninsulated, drafty, intolerable in high Summer and deep Winter. Here I begin demolition of flimsy paneling. The work followed thorough insulation of the upper attic and all  other kneewall closet floors, with imperfect treatment of all challenging heat bleeds of bungalow construction. Work done in 2008 is reported here in 2018, as example of best-effort coping with difficult-to-insulate bungalow construction, vs. better practice of raising the roof as an ordinary attic over a full second floor.

My method is durable, unlike found flimsy layup of paneling with nails. And yet, it is not honest treatment of all second floor heat bleeds.

Brittle stiff paper behind the paneling removed, a surprisingly full fill of cellulose on this gable wall only, tumbles down. See that insulation blown from outside with ending any hope the exterior sheathing is air tight, failed to treat very leaky non-insulation about the rough frame of a remodel vinyl window. Insulation was almost entirely bypassed by convection and large leakage-movement of conditioned air, between buckled stiff felt paper, and the flimsy wood-panel sheathing of the knee walls and ceiling.











See that I had previously insulated the ordinary floor of the upper attic, and had air sealed and stuffed floors of knee wall closets.

I am quite displeased with my leaving of perhaps-useless paper-faced mineral wool batts upon the second floor attic walls.





















See my placement of R15 kraft-faced batts with full filling against roof sheathing. In 2x4 space thinner insulation as with joke "R13" - - must not be commanded to cool  the roof. Allowed convection in foolish and ineffective deference to composition shingle warranty, ruins any insulation value. R15 was little enough, to be achieved. See that some odd roof pitches challenge the imagining of how to place batts.  Did I do right?

 























Know now that the kraft facing is nearly useless as an air and vapor barrier. I want both.

Apply then, Tenoarm 6-mil virgin polyethylene vapor and air barrier. Lose my shirt with the immense difficulty of setting strong GP Densarmor drywall. Accept meager payment that was larger than the customer wished. Learn that the room was nice for a family with a little girl, now grown. A heat bleed remains in the triangular wall to left in the photo above, where a difficult, expensive trapezoidal door, was not afforded although framing of the door was provided, just needing a cut through the drywall.

Might the new home owner now wish to raise the roof, for more living space, in a home where rent-out of portions is in great demand?

Insulate Exterior Wall of a Bathtub or Shower

At 3/3/2026 add a temporary message to my loyal reader in Ashburn VA, who consulted this post on 3/2/2026. By chance today I talked with a sales consultant at prominent plumbing supplier George Morlan, in Portland, Oregon, about this post. I have relied on Geo. Morlan for all of my important plumbing purchases, including the Kohler bathtub. I wanted this supplier to be aware of and to promote my solution in promise of never relying on caulk as a water barrier. I described the copper strips and two-part epoxy adhesive sealant. The response was dismissive. 

My plumbing suppler assures that  tub design is for placement directly against wall studs. Butt-placed drywall is set against the 1/2" thickness raised edge perhaps 1/2" tall.  Not so, I say. I offer my argument with some new illustrations.

Absent the copper and epoxy, with sure-to-fail ugly staining caulk, water would wick past the tub rim. 

The airy space under the tiles bottom edge stays clean and  in shadow has the appearance of the tile grout. The wall stays dry and healthy. No ugliness, ever!

Outside walls should be insulated and hard-covered before a bathtub or shower unit is placed. Here is a reverse-chronology abbreviated photo album of my trial of methods, where I demand hard backing for wall tile. 

Here are all photos split into three groups:

First Sixty

Second Sixty

Third Sixty

I really, really want feedback for my effort in the job and in this post.

I use two layers of 1/4" backer board, for reasons including secure tile overlap of a copper seal edge. 

Here are drawings detailing the tiling about the Kohler bathtub:

Kohler Wall

I will not rely on tile or caulk in sealing the tub edge. Here two-part epoxy seals a copper edge to the tub lip and exposed areas of the backer board.

After several trials, I chose a Kohler porcelain tub of ordinary height, with sharpest inside corners. I believe least maintenance and best suitability if handicapped, is with a tub this height, with good shower curtains, not glass doors.



See the pencil tracings on backer board above? Yes, my plumbing supplier took in exchange, an undamaged too-tall fiberglass Maax Skyline tub. I thought the Maax tub flanges would be conducive to edge sealing, but they are not. I find no tub built to not rely on caulk. The copper idea was volunteered by friend Copper By Design. I inquired about stainless steel.

Tiling was done atop ultra-flat 3/8" ACX plywood framed below as a strong and flat table. Bottom tiles will rest on the plywood, and that tile rest edge will remain exposed out of sight, sanitary with full gap filling of flexible grout. Flexible grout has added mildicide. I offer free samples and seek to inspire manufacture of the versatile flexible grout, at blog plasterrepairhowto. I report that anyone may apply a commercially-available equivalent, Custom Pro Tile Grout. Pack grout only to the tile edge under-side, sparingly.

My material, in other applications, has advantage in being sandable-like-drywall-mud. I appeal to Custom, to offer that product.

The finished bathroom outside wall.

The tile is backed with plywood set in the walls, and two layers of 1/4" backer board. Many screws ensure tiles and grout should never be distressed by any action in the wall. Thermal stability with the insulation will help too. 

The plywood is 3/4" thickness and should have extended to the ceiling, for secure mounting of the outer layer of 1/4" backer board even where there are no tiles. This plywood is moderately-well fastened. It may not adequately support grab bar attachment points. I might have toed many more screws to lock plywood to the joists. I could have taken more space, facing 3/4" plywood sheets against the wall joists, for mounting of whatever, anywhere. Think and do not fail to learn. More-ideally, plan grab bar attachment points of solidly-mounted 2x lumber.

Vapor Retarder Two-Thirds Rule

When placing insulation in Portland, Oregon, I rarely use material with a bonded-on vapor retarder (kraft face). I am aware of propaganda favoring cellulose, and raising fear of fiberglass batts, in The Big Burn Video. Proponents of cellulose have dealt with criticism of organic cellulose as inherently less safe than inorganic mineral insulation, and tilt the table too far in the other direction. The video presents ideal cellulose, and fiberglass with no description. I imagine the fiberglass was a least-favorable setting, with air channels (chimney path) the length of flammable kraft facing. A fair comparison would have fiberglass totally filling joist bays, with no kraft facing.

I will never use kraft facing in a wall or in a new-construction ceiling. There I use complete, taped sheathing with polyethylene sheeting designed for the purpose, Swedish Tenoarm. Aside from fire safety concern, I save time and get better fit, in custom-cutting unfaced batts. I also follow the advice of the USA importer of Tenoarm:

http://www.conservationtechnology.com/building_design.html.

I will use kraft batts in an attic floor, to isolate new material from found loose-fill insulation. I use original reasoning in study of dew point data for my location, as reviewed in this posting, with a current update. The commonly-understood two-thirds rule states that a vapor retarder should be to the warm side of two thirds of the applied insulation.