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General Concern - Insulating 120 year old walls


Inindo's Avatar
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01-02-16, 04:00 PM   #1  
General Concern - Insulating 120 year old walls

I am insulating the attic on a small (under 1,000 square foot) house built in the 1880s. But, now that I am up in the attic, rolling r30 batts between the joists, I was thinking about the walls.

Has anyone had negative experiences insulating walls on an old home? I was thinking of blown-in insulation. But I read nightmares about the insulation growing mold.

The exterior walls of the house are lath and plaster, with real 2x4 framing. The siding is redwood lap. There should probably be some kind of exterior sheathing, but there isn't. House is in Los Angeles.

I noticed in the attic the top plate is 2x3 atop the 2x4 studs. I was wondering if the 1" gap, which I can look down from the attic, was intentional for ventilation?

I am hesitant to pump insulation into the walls as it hasn't been there for 120 years - kind of don't rock the boat mentality.

Thoughts, comments, or stories would be appreciated.

 
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01-03-16, 03:59 AM   #2  
Is the house more than one story tall? If so, it could be balloon framing. One obstacle you will encounter in older homes is perlins across the stud bays about 4' off the floor. Blowing insulation only from the top will leave 4' of uninsulated space at the bottom. Generally, once all the framing is determined, a contractor will drill 1" holes every 16" (or in the center of each stud bay) at the top and midpoint from the inside (yes in the plaster and lath) and blow insulation in, repairing the holes when finished. We can't see it, but it is one option.

 
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01-03-16, 11:28 AM   #3  
Yeah, it's tall, steep roof, decorative Victorian house. Technically 1 floor, but ceilings are 13' on first floor, and attic is 13' too. It's taller than my neighbors 2 story home.

Perlins are the diagonal framing members I assume? I see them when people have their siding removed. I looked up perlins/purlins, lots of Google images look like they're roofing members (look like 1x3s across the rafters).

My studs are sometimes 24", in other places 16". Like I said though, that gap in the top plate makes me feel the walls shouldn't have insulation. Wonder if it helps move air?

 
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01-03-16, 12:04 PM   #4  
Wonder if it helps move air?
The ideal solution is to prevent air movement, so that theory may have been of the 1800 thinking genre. Perlins are horizontal "fire stops" running between studs. They would stop you from installing insulation from the top for complete coverage.

 
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