Insulating a 1890 balloon-frame Chicago house
I have a couple questions about my 1890 balloon-frame house.
It is a wood balloon frame house with 1″ thick sheathing boards 8-10-12 inches wide. The original siding is a wood clap siding with a paper under it – later the house was covered in a type of tar paper and wire mesh to add a 1 1/2″ cement stucco in a brick pattern (one piece shell) — to give you an idea of outside make up.
I took off some plaster walls in my office to replace with drywall since they were starting to fall off and while those 2 walls are open I figured I would put some insulation in there before the drywall.
Then I got into reading about balloon framing and insulating and now I have more questions then ever.
These walls do have some blocking in the wall by the floor going into the basement with wood which I plan to shoot some foam around the edges of the wood to air seal it better
My question is – is insulating my house a good idea ? I have read about sealing up the outside walls and then they don’t breath and then have read that sealing is a good idea ?
The sheathing boards have gaps where they meet each other and I was thinking of shooting some foam in those gaps to help with air coming in the wall (which there doesn’t seem to be much probably cause of the outside cement siding ) most air seems to come from basement
Then I was gonna add some r13 fiberglass insulation in the wall cavity with the vapor paper facing the inside of the house under the drywall
Is this a good plan ? Air sealing the gaps in sheathing and fiberglass insulating ?
Also when work in attic is completed (electrical and such) I plan to go around and seal all the gaps and holes in the tops of the walls to seal the attic and have someone come in to blow cellulose insulation in
Any info that would help me plan my house insulation and can get these 2 walls sealed up would be great
Thanks David
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Since you have the clapboards to maintain an air gap to the stucco layer it's a pretty good capillary break. It's better if the space between the clapboards & stucco has some vent holes at both the top & bottom to slowly replace that air with outdoor air via convection but it's not absolutely essential.
You absolutely DO want to air seal the walls from interior air migration, since wintertime indoor air's dew point is well above the temperature of the average temp of the clapboards & sheathing. It's fine to seal the gaps in the plank sheathing with can-foam.
Kraft faces R13s are probably not the best solution here. Most 1890s balloon framing used full-dimension 2x4s not 1.5" x 3.5" milled lumber, often with random spacing too. A batt designed for 16" o.c. and milled lumber studwalls will have huge gaps, and will not perform anywhere near it's R-rating due to thermal bypass & convection currents within the space. A better solution would be to staple up some mesh and blow it full of cellulose, but if you're doing it a room at a time and would have to rent the blower that's a non-starter. If batts are the only possiblity, go with unfaced R20s designed for 2x6 24" o.c. framing and carefully sculpt them to fit the width, and install a smart vapor retarder over it detailed as an air barrier. (Certainteed MemBrain is about $110 for a 10' x 100' roll, available at some box stores. Sometimes Menards has 8' x 100' rolls available online for about 100', but both Lowes & Home Depot are starting to carry a few sizes in my area, and can probably be ordered on line.) The air tightness of a broad-sheet air barrier is far superior to anything you can do with a kraft facer (which is also a smart vapor retarder, but impossible to make air tight.)
You'll have to carefully seal around any electrical boxes and penetration, and sculpt the batts to fit without gaps, and tape the electrical boxes to the vapor retarder in an air tight manner etc.
With R20s it will be a compression fit when you put up the wallboard- it's fine if the vapor retarder is wrinkled in the process. When you compress5.5" R20s (R3.6/inch) down to 4" it's R per inch goes up to R3.8-R4/inch so you'll be in the R15-R16 range. But the air-retardency of that compressed batt will be significantly better than an R13, even a perfectly fitted R13, so the effects of air leakage into the cavity from either side will be much reduced.
Thank you for the info - I thought compressing the insulation down was a no no? - I measured the studs in my walls and they are a ruff cut 2x4 in this room but are 3 1/2 deep (maybe a 1/16 over) and all are super close to 16 on center except for a few 8 or 10 inch in corners or by door and Windows
Was thinking of blown in but like you said renting the machine makes it cost a lot in long run
Under the stucco the wire was spaced a little bit when they put it on 1/4 inch or so and since it's a wood siding it does have some space where they overlapped (had to remove some of the brick and reinstall)
I was worried about sealing up the gaps in sheathing and cause the wall not to breath - glad to know I can seal them up - sounds like the biggest place I need to worry about is the air coming from the basement since its decently warm down there
What I have done in the past other houses was put the batt with paper face in the studs and put the paper flaps over the stud and Chris cross one flap over the other when stapling thought when the drywall got screwed down it would seal pretty good but sounds like you don't think so - should I tape he seams ? Or is the unfaced and separate air barrier that much better ?
David,
Q. "I thought compressing the insulation down was a no no?"
A. It's OK to compress a fiberglass batt. Compressing a batt reduces the R-value of the batt, but raises the R-value per inch.
Q. "What I have done in the past other houses was put the batt with paper face in the studs and put the paper flaps over the stud and criss-cross one flap over the other when stapling. I thought when the drywall got screwed down it would seal pretty good."
A. You have described a good method for installing a vapor retarder. The kraft facing works fine as a vapor retarder when installed the way you describe. But this method does not create an air barrier. If you want to reduce air leakage, drywall is a better air barrier than the kraft facing. If you focus on making the drywall as airtight as possible -- by limiting air leakage at electrical outlets -- you'll end up with a better installation than you would if you tried to make the kraft facing airtight.
Here are links to two articles that provide more information;
Questions and Answers About Air Barriers
Airtight Drywall
If the studs are pretty close to 3.5" deep and not wider than 1.75" you can install standard batts without too much sculpting. If they're a nominal 2" wide with 14" or less between the studs you may have to trim the batts a bit to get them to fit without a wrinkle or buckling- the goal is no air gaps, pockets or compressions where air can move. Standard batts are manufactured 15"wide, designed for a snug fit without buckling into a 14.5" nominal cavity width. Rather than kraft faced R13s it will be better to install high density R15s (rock wool or fiberglass) for their higher air-retardency, along with a broad-sheet vapor retarder such as MemBrain. It's more expensive than a contractor-roll of R13 but probably worth it.
Take the time to fit the batts carefully. True perfection is impossible, but if you take the time to tuck in every edge & corner to ensure that it's in contact with the sheathing without any gaps at the framing, then gently tug them out so that they're just proud of the interior stud edge you can do pretty good. Split the batts to accommodate wiring & plumbing, and take the time to make the electrical boxes air-tigth (or replace them with air-tight electrical boxes.)