insulating balloon frame w/ brick veneer

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Old 11-04-13, 07:18 PM
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insulating balloon frame w/ brick veneer

I'm currently renovating my 1909 home in SW Pennsylvania, which is a three-floor balloon frame building with brick veneer on the first two floors. I just gutted the second floor bedroom down to the studs. I would love some advice on how best to insulate (or not insulate at all) the walls.

The exterior walls are constructed as follows: brick, ~1" cavity, ~1" thick wood plank sheathing (laid horizontally across the studs), 2x4 studs, wood lathe, plaster. The sheathing planks have variable gaps running between them, from 0" to about 0.5". The studs run all the way to the foundation.

The original plaster and lathe has all been removed. My original plan was to put batt insulation in the interior wall cavities before hanging blueboard with veneer plaster. After doing some reading though, I am concerned that filling the wall cavities could create moisture problems. There is a cavity between the brick and the sheathing to keep the batt away from the brick. Would that be sufficient to provide proper airflow, or should I keep the interior wall cavity open and just hang the board over it?
 
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Old 11-05-13, 03:53 AM
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Brick is difficult as it has lived with the heat and air flow for 100 years. I have two links that will help you understand your options.

The boards and gaps will expose the batt insulation to air movement which will reduce its effectiveness. For insulation I would prefer Roxul, a dense mineral wool.

As for the balloon construction, it is necessary to provide fire blocks across each stud bay at each level. Check local codes for max height, but it is necessary to slow (heaven forbid) a fire.

Happy reading
Bud

BSI-047: Thick as a Brick — Building Science Information

BSD-106: Understanding Vapor Barriers — Building Science Information
 
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Old 11-07-13, 05:10 PM
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Thanks for the info, Bud.

I've glanced through BSD-106 previously, but in most of those scenarios I am limited by an inability to do anything with existing exterior wall (i.e., I can't add vapor retarder or rigid exterior insulation between the boards and brick.) Reading it more closely I'm starting to understand the principles, though. Definitely something to think about.

Roxul is a great recommendation. I was considering UltraTouch denim before, but Roxul definitely looks like a superior product.

Fire blocking has been on my mind as well. An article at JLC indicates that mineral batt is an approved fire blocking material. I plan to ask around locally to see if something like Roxul would be acceptable to our inspectors.
 
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Old 11-07-13, 06:50 PM
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So, how will you insulate it?


Gary
 
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Old 11-08-13, 05:05 AM
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Fire blocking is not hard to install. Locate it where you plan to have a seam on your drywall so it serves two functions. As for the Roxul, you may need to space it for a tight fit. If those old 2x4's are a full 4", the 3.5" insulation may not be tight. Old homes require a lot of attention to details and fudging to compensate for dimensional materials.

What you can do with the exterior walls is preserve the air gap behind the brick, between the brick and the board sheathing. Make sure it has an air path to allow air in and out once you seal and fill the cavity. Others can correct me (please), but I would cut and fit panels of house wrap in each cavity. Glue and staple to the studs on each side. That will provide a moisture permeable air barrier to protect the cavity from air but allow drying to the outside. As long as the bricks have an air gap for drying, the boards will benefit from the same. They have survived this long in that position.

If the inside of any exterior walls have space you can add 1" of rigid foam before the drywall to reduce the thermal bridging. Adjust electrical boxes as needed and decide what you will do around doors, windows, and the floor. Use fire rated caulking to seal any holes for electrical or other.

Bud
 
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Old 11-10-13, 02:22 PM
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Lol, Bud, I meant the OP.

What you have suggested is fine. BSC in this link, Fig.9 shows for a cold climate behind brick/air space- ply or OSb (0.75 perms); then cavity insulation of low density (0.5#)SPF then asphalt faced paper or MemBrain v.r. You could use EPS rigid f.b. (3 perms), and compressed f.g. (R13 = R-10) plus EPS (3 perms) on the face for thermal bridging as you suggested. Total perms= 1.5. IMO, use some XPS (1.5 perms twice, as said; one layer on the wood sheathing, one layer on the stud faces for total 0.70 perms at R-20 whole wall. ADA the drywall.It could still dry to the inside with a perm rating similar to cavity ocSPF or a faced batt as pictured. Fig.9; BSD-012: Moisture Control for New Residential Buildings — Building Science Information

Owens Corning Fiberglass Batt Compression Chart - Num Sum

http://commercial.owenscorning.com/a...35d75090ec.pdf

Info-401: Air Barriers

Gary
 
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Old 12-07-13, 07:21 PM
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Hey guys! Sorry I left this thread idle for a while. I really appreciate your advice and didn't mean to ignore it. It's just that some more pressing issues came up and my insulation project got put onto the back burner. Finally ready to move ahead now though.

I like your recommendation to use XPS.

Based on what you guys told me so far, my plan of action is to put 1/2" XPS directly against the existing wood sheathing, and then follow that with 3.5" R-15 ROXUL. That should fill the entire 4" wall cavity.

There will then be some space to play with on the stud faces. The existing window frames extend about 3/4" out from the studs (old plaster & wood lath was removed). So, I can do another layer of 1/2" XPS followed by 1/2" gypsum board, butting up against the frames where necessary. That will leave 1/4"-5/8" to make up with trim around the windows, depending on the thickness of the veneer plaster.

Is FOAMULAR Insulating Sheathing the right product to use?

Let me know if this sounds like a solid plan!
 
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Old 12-10-13, 03:16 PM
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I don't like rigid foam on two sides personally but Gary does know his numbers and application.

I would prefer to leave a small air space between the sheathing and the XPS to allow the sheathing and brick some vent space. Something akin to a reverse rainscreen but for air movement. Seal all the seams in the the stud cavity at the XPS to stud connection and make an air tight wall assembly. This will keep the moisture from inside out of the wall and allow the wall to dry to inside when it needs to.

Something about older brick veneer and changing the breathing that gives me a bit of misgivings.

Gary's way will work 100% as well but I have usually done it this way.
 
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Old 12-13-13, 10:42 AM
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I would prefer to leave a small air space between the sheathing and the XPS to allow the sheathing and brick some vent space.l
I considered that as well. The problem is I have 4" of cavity to work with, so leaving a gap would require the Roxul to be compressed. That's not necessarily a showstopper, but I'm also concerned that moisture condensing on the cold side of the XPS would run down and then pool at the firestops (between XPS and sheathing).

I guess moisture could still condense between the XPS and sheathing even if they are right up against each other, but at least it won't pool as badly. There is already an air gap between the brick and sheathing, so hopefully that will provide enough ventilation and drying action. The last thing I want is for the 100-year old wood to start rotting.

Does that make sense?

As far as XPS on two sides, is your concern that it would create a double vapor-barrier? One of the documents that Gary posted stated that XPS doesn't necessarily create a double vapor-barrier. Although, that seemed to assume that there would be a lower-perm vapor barrier like 6 mil poly on the warm side of the wall. It didn't specifically apply to using two layers of XPS. With that in mind, would it make sense to remove the plastic facer from either layer of XPS so that one is more vapor permeable than the other?

I'm heading to Lowe's today to pick up materials, and hoping to get started on the work tomorrow. If you guys are still with me and have any final thoughts, now is the time to chime in!
 
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