Author Topic: Insulation question- This Old House  (Read 739 times)

accolay

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Insulation question- This Old House
« on: March 02, 2017, 01:53:44 PM »
A renovation project. Unfortunately had to tear out some plaster and lath (not all-I like plaster walls) due to the crumbling nature of it since original owner at some point let the roof go/water intrusion...etc.etc.

The insulation question involves the vapor barrier question. The inside walls are lined with tar paper. Outside walls were lined with tar paper, then wood siding (I think most is still there) then lined with some kind of old aluminum lined barrier fabric, then sided with wide 50s/60s/70s asbestos siding.

My question is....do I cut out the interior tar paper then put down faced insulation batts...or unfaced batts with additional plastic vapor barrier...or what. Drywall will house

I find it very confusing, and reading up on the subject through building science, green building advisor and others makes me more confused instead of less. This house is in Minnesota, warm humid summers with air conditioned interiors, cold winters with dry warm interiors.

Lulee

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Re: Insulation question- This Old House
« Reply #1 on: March 02, 2017, 04:42:21 PM »
I've never heard of such an arrangement, even on some old houses I've been around, including one old shack that was converted from housing pigs to people.  Looking forward to hearing from more experienced folks like paddedhat who might have seen this before.

Could you skip the entire issue by stripping down to the exterior wood cladding and then going with spray foam insulation?  This would give you an air infiltration and vapor barrier all in one along with a better R value than the batting.

accolay

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Re: Insulation question- This Old House
« Reply #2 on: March 02, 2017, 05:31:09 PM »
Definitely could go with spray foam int he walls, but there is the cost issue. I am having the rafters and probably the rim joist spray foamed though.

Lulee

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Re: Insulation question- This Old House
« Reply #3 on: March 02, 2017, 09:36:13 PM »
I believe there was a discussion a while ago about diy spray foam insulation in this sub-forum.  My takeaways were 1) it is possible and makes it more cost-effective and 2) definitely to use the head-to-toe coverall as it's a right misery to get the stuff out of your hair once it hardens.

My limited understanding has been that the vapor barrier goes between the insulation and the outside.  This keeps water intrusions and moisture away from the insulation where it can molder.  The inside of the insulation is left to breathe and dry to the same moisture level as the house interior.  No idea how you could manage this in your situation.  The outside layer of tar paper on your house would help protect against any water that squeaks in through the siding layers but it isn't a proper vapor barrier.  Perhaps it is enough though?

Fishindude

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Re: Insulation question- This Old House
« Reply #4 on: March 03, 2017, 07:05:27 AM »
When remodeling old houses like that I recommend disturbing as little as possible.   If you've got the plaster and lath stripped off the inside, down to exposed studs, just do you wiring, stuff the stud cavities with fiberglass insulation, then install your interior drywall or wall material.   In some cases, I've actually removed the wood trim and laminated a layer of new drywall right over the old cracked plaster.  It worked out good for me and a screw will catch just about everywhere as it's solid wood lath behind the plaster.

paddedhat

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Re: Insulation question- This Old House
« Reply #5 on: March 03, 2017, 07:11:46 AM »
Honestly, no offense to anybody here, but I wouldn't ask a question like this on anything but a building sciences forum, then I would simply ignore anybody who I couldn't vet as an expert, in the responses. As you are probably aware, your question is highly complex, and the variables are numerous, including everything from your location, to the smallest of original construction details. The materials and methods you choose can be wildly successful, or literally destroy the building. As a result the true experts in the building sciences field, like all good scientists, are constantly reviewing and challenging their ideas of best practice. Comments like, "well that didn't work as well as we hoped, so try this", or " this method is now generally accepted as a disaster in climate zones 5-8, but can preform well in southern zones" are common.

Incorrectly placed vapor barriers, spray foam, and/or high density cellulose installations have all successfully destroyed buildings. Doing so by creating conditions where brick exteriors spalled, cracked and eroded to the point that hundreds of years of wear occurred in the few years. The same products and techniques have caused mold growth and moisture damage in the walls of wood frame buildings to the point that demolition revealed severe cavity rot, mold and trapped moisture, rendering the building uninhabitable. They have also created conditions where wonderful old buildings no longer can keep a coat of paint on them, since the vapor dynamics have been altered, and wall cavity moisture in now migrating through the paint, and rotting the siding underneath. Sadly, the "cure" for this is often to hide the ongoing failure under vinyl siding. This is an logical as curing a lung infection with a nice new sweater. Oddly enough, the same techniques and material have been highly successful in other applications, other homes, other locations.

 Currently, for the first time in my life, I'm doing battle with a sweet mid-century ranch we just bought. It is the first old home we ever bought, and in many ways it's an amazing place. Unfortunately, in the 1950s, there was no need to worry about heating costs, since oil was dirt cheap, so the place not only has no insulation in the walls, and no hope of putting any in. The place is built of block, with a brick exterior and furring strips and plasterboard nailed to the interior. Now if you live in Fl. or AZ. you might say, "what's the issue?" but this place is  located 1000 miles north of there, on the east coast. While doing a lot of the same research the OP is doing, I found that best practice is to gut the interior, build stud walls an inch inside of the block, and spray at least R-10 closed cell foam on the block wall. Second choice, at a much lower cost, is to demo. Attach 2" of extruded poly to the walls, and stud frame the interior. Now there are two huge issues here. First, the interior of the home needs to be destroyed and rebuilt to accomplish this task. Second, the end result, according to a white paper from the DOE, is that I can look forward to a 9% reduction in heating costs. I about fell out of my chair when I read that figure, for two reasons. First, the savings are nearly negligible,  and can be offset with things like a smart thermostat, and savvy buying of heating oil. Second, after destroying and rebuilding the interior of this home, my payback would probably work out to forty or fifty years, if ever. The fascinating part of the whole concept is that doing this type of retrofit to an existing brick building can, and has, destroyed many beautiful old brick structures. The reasons are complex, and basically boil down to. it would probably work fine given the specific details of my project, including location and condition of the structure. However, five hundred miles north, on the New England coast, with a building a century older, it may very well destroy the exterior in a few years, by compromising the ability of the exterior wall to full dry between rains, or snow, and leave saturated bricks to freeze and decompose.

In closing, I don't have an answer for you, I'm literally not smart enough, or well educated on the subject. Which you will find is a problem with 95% of those who you will deal with on the topic, ESPECIALLY insulation, remodeling, siding etc... contractors. I do know that there are many folks in you situation that have done energy audits, followed by comprehensive sealing and weather-tightening of the structure. The results can be shocking, and often result in a home that is totally comfortable, and much cheaper to heat, without going down the rabbit hole of, "will I totally F this home up by filling the walls with X,Y or Z, and who can I trust to give me the right answer to that question?"

 As for specific recommendations, I would do the following, based on the assumption that you are keeping the majority of the exterior and interior wall surfaces intact. First, get an energy audit with a blower door test to see where the place is leaking. Next go gonzo on obsessively sealing everything and anything that leaks, doors, windows, electrical outlets, baseboard, rim joist, attic access, everything.  Next, if needed, install quality triple track storms on every window, and good storm doors on every door. Finally, air seal and insulate the attic to the highest standards possible. In many cases this can result is savings of 50% and more on energy bills, and totally improve the "feel" of a drafty old place, which for a lot of folks makes the wall insulation problem go away. Good luck.

J_Stache

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Re: Insulation question- This Old House
« Reply #6 on: March 03, 2017, 07:22:04 AM »
I find it very confusing, and reading up on the subject through building science, green building advisor and others makes me more confused instead of less. This house is in Minnesota, warm humid summers with air conditioned interiors, cold winters with dry warm interiors.
Three points:
1. If you are only repairing a small section, it won't matter what you do, since the rest of the house will remain as it was.
2.  I'd ask the question on GBA (http://www.greenbuildingadvisor.com/qa) instead of trying to find a similar situation via search.
3. Buidling Science has great write up that should help you understand vapor and air barriers and climate zones: https://buildingscience.com/documents/digests/bsd-106-understanding-vapor-barriers

accolay

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Re: Insulation question- This Old House
« Reply #7 on: March 03, 2017, 03:03:44 PM »
Thanks for your responses. Paddedhat... I know, right? You must read Bob Yapp's blog. I also feel like many contractors either don't know about these issues, or don't care. I'll check out those other forums.

Fishindude...I agree with doing as little as possible. I love historic homes and hate that too many are screwed up (don't get me started on replacing original windows). Unfortunately it was not an option in this case in these areas, as it's another semi-bastardized house, in a cheap/poorly built house to begin with- you can see it in the plaster installation, i.e. the keys pushed between the lath or lack thereof. The two areas in question are the bathroom and kitchen. The bathroom had the glued-on faux tile stuff...when I removed it it took off the finish coat of plaster. Then I found the rear stud wall had the studs flipped...how do I say this...so the plate was on edge and the studs instead of perpendicular were in line with that. Anyway, the result was that when I pushed the entire wall moved. This is the wall behind the tub and I didn't want to tile a moving wall. It's rebuilt.

The kitchen already had the plaster removed on one wall and re-drywalled. The top of the wall had faux brick stuff at the top two feet.

Beyond those rooms, the ceilings in the kitchen and bedroom they had covered with acoustic tiles to hide existing plaster damage. I took it off (not conducive to cleaning off cigarette tar). To install those, they hammered 1x4 strips along the ceiling to hand the tiles, further ruining any good plaster. The water damage was about 50% of the ceiling already, with nail damage, probably only 25% left was good plaster.

Like pealing back the layers of an onion in remodeling old houses, especially when previous owners had bad ideas, or didn't do maintenance (second house where owners let the roof go too far.)