I own a 60s vintage ranch house, conventional frame construction of the day. It seems that it is sheethed with a gypsum product of unknown thickness. The original composition siding was overlaid long ago with aluminum. There is no sidewall insulation; moisture barrier is anybody’s guess.
I want to insulate the sidewalls and eventually replace the siding. My default thinking was to remove both layers of siding and use blown-in cellulose or fiberglass insulation. Then possibly add some rigid foam and/or Tyvek. Final siding is not yet decided.
My main question for the group: Should I consider replacing the gypsum sheathing with something more energy efficient. I really don’t know what is available. My gable ends have no overhang so total thickness with the roof edge is a limitation. If the gypsum is removed, I’ll have to provide diagonal stability. Can steel cable or flat stock be used for this? I’m unsure yet if I need a permit or code inspection.
If I replace the sheathing, I have a lot more options for insulation and getting a very tight job.
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you don't say where you are climate-wise. This is critical to some of your theories proposed.
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I am located in south central Pennsylvania. It gets kinda cold and damp here. (Right now it's hot and damp.)
OK, for a cold climate like that you want the foam on th einside of a wal, not overlaying the exterior where it functions as a VB and traps moisture in the wall cavity.
You can have cellulose or chopped FG blown in without removing the gypsum sheathing you have there. I would want to avoid losing whatever shear strength that provides, even though you probably don't have much worry about hurricanes or seismic action.
Of course, by the time you demo two layers of siding over that gypsum, you may not have much left and would need to replace it with sheathing, but I would do that a few sheets at a time to avoid wracking the house
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Ok, thanx for those good points. I have a rudimentary understanding about moisture and air flow. What about housewrap? There are several types/brands, Tyvek being best known. Does it breathe enough for this application?
My thinking has gone something like this: Remove the two layers of siding and whatever vapor barrier might be there (most likely felt.) Fill my stud bays with blown-in insulation. If possible, apply another layer of suitable insulation <1" thick. Wrap with house wrap. Apply (probably) vinyl siding with whatever spacing/ventilation is needed behind it.
Do you see any flaws in this plan?
Flaws - maybe.Housewrap should go on under the foam, IMO.With adding the foam over the gypsum sheathing you leave me wondering what you will find to nail the vinyl siding to. you may need to add furring strips creating a rainscreen wall.Adding up thicknesses can make you have problems detailing at the windows.here is another thread on similar subject matter.
http://forums.taunton.com/n/mb/message.asp?webtag=tp-breaktime&msg=94278.43
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