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Thread: Insulating old house

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    DIY Senior Member Master Brian's Avatar
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    Default Insulating old house

    I have a 1915 Craftsman style Bungalow with clapboard siding. I know the walls aren't insulated well/if at all. I am also pretty sure there is no sheeting under the siding, as when I went to drill a hole for a bathroom vent, it was siding then empty wall spac.

    I am going to be doing a paint job this spring on the outside of the house and have a few thoughts....

    I am pretty sure I can pull one or two rows of siding off in a few areas to get access to the inside of the walls and if not, I am thinking I can take my 2" hole saw and just drill holes at every cavity, then replace the plug, fill and sand. The 1st method would be the cleanest and quickest if it works like I think it will, but I know I can do the 2nd method.

    My questions are what type of insulation should I blow into the walls? I still have the lath and plaster and don't want to create any issues with it. I have thought and read about the foam, but think it might be too risky and expensive. At this point, anything is better than the dead air space I have as insulation now.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    My thoughts...without a vapor barrier, you risk rotting the structure if you use something like cellulose. A closed-celled foam might qualify as a vapor barrier - you'd have to check carefully.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member Master Brian's Avatar
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    Quote Originally Posted by jadnashua View Post
    My thoughts...without a vapor barrier, you risk rotting the structure if you use something like cellulose. A closed-celled foam might qualify as a vapor barrier - you'd have to check carefully.
    Can you explain?

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    DIY Senior Member Master Brian's Avatar
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    When I ask to explain, maybe I should clarify...

    I understand the vapor barrier keeps moisture and such at bay, but I thought cellulose was good at combating mold. I'm sure the spray foam is out of the question do to cost and the fact, I probably won't/can't do it myself due to lack of tools for that job.

    I guess I hadn't thought of the vapor barrier angle as I've just heard and seen of others doing this often. How do you get around the vapor barrier and/or how do you determine if it's needed?

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Insulation moves your dew point (the point where condensation occurs), and without a vapor barrier, it could end up inside of the wall. Cellulose doesn't allow air movement much if installed properly so that helps, but if the cellulose gets wet from condensation, it will take forever to dry out. It might not mold, but the wood, can.

    There are companies that sell spray foam in large kits in various configurations that are much more ecconomical than little cans and maybe a contractor doing it. It can be a messy job, and you need to be careful not to put in too much, or you can split walls, break windows, bow walls. But if you follow the instructions and pick the proper foam to do it, you shouldn't have problems.
    Jim DeBruycker
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    Jack of all trades frenchie's Avatar
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    Aside from the vapor-barrier - what about a weather-resitive barrier?

    If there's no sheathing, and you have any leaks in the siding... right now, water gets in but also gets out, and there's possibly enough airflow to dry things out. But if you stuff the cavity with insulation, especially a non-waterproof insulation like cellulose... your house will rot.

    The right foam for this situation is poured, not sprayed, and it's pretty expensive. And if there's no WRB, or if the WRB is degraded, you'll still have moisture coming in via the studs; more to the point, you'll be effectively glueing the siding on, good luck with any repairs later on.

    Sorry, but the only really correct approach, is to pull the siding completely. Insulate, sheath, wrap, and re-side.
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    Quote Originally Posted by Master Brian View Post
    I have thought and read about the foam, but think it might be too risky and expensive. At this point, anything is better than the dead air space I have as insulation now.
    Keep in mind there is more than one kind of foam. There are expanding (looks like shaving cream) and non-expanding foams. Within the expanding category, there are open and closed cell varieties.

    If you're worried about blowing the plaster and lathe, you can use the non-expanding variety, e.g.:

    http://retrofoam.com/
    http://www.usainsulation.net/

    Expanding:

    http://www.demilecusa.com/
    http://www.icynene.com/
    http://www.emegabuild.com/

    DIY kits:

    http://www.tigerfoam.com/

    FWIW, I used expanding foam (Demilec) on plaster and lathe in my finished attic, and only had a problem over one window. I figured that plaster would have needed repair anyway, so I'll just put up some blueboard and get it skimmed when the rest of the room is finished.

    I didn't have any problems with the underside of my roof deck blowing out any plaster. An experienced insulation contractor should be able to advise you. I certainly wouldn't discount it before talking to someone who has experience in retrofitting insulation. You may very well be fine.

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    DIY Senior Member Master Brian's Avatar
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    Frenchie, You are probably correct about the leaks, I had thought about that. I haven't decided what I am doing yet, but I will say, when I paint, there won't be any gaps/cracks anywhere I touch. I plan on using expanding foam spray and 50yr caulking throughout. With that said, I realize there is always the potential for a shift or crack to occur that I miss.

    I don't see any future concerns regarding "glueing" the siding on with an expanding foam, as this is the original clapboard siding and I don't ever plan on replacing it!

    I also checked on a few of the foam products and haven't found any dealers in my area, but I may call them next week and see what they say.

    Tearing the siding off is a thought. I just wonder how much work/trouble it would be furring the windows and such out to account for sheating. Hmm... Siding in and of itself doesn't scare me one bit, as I used to be a siding sub on new construction for a few years. Problem is I've never messed with the clapboard much and I want to keep this original siding.

    Let me ask this, is there some wrap that I could possibly use in place of using sheeting? I know sheeting would be preferred, but.......

    If I pull the siding off, should I just install fiberglass batting? I know the sprays might be more efficient, but I am not easily convinced all of that type of stuff is really worth the added cost. I'm sure not paying someone $10k+/- to insulate my house. The other thing I worry about is getting this house too tight and causing issues. These old houses are designed to breathe.

    Thanks for the things to ponder....

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    Jack of all trades frenchie's Avatar
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    Quote Originally Posted by Master Brian View Post
    I don't see any future concerns regarding "glueing" the siding on with an expanding foam, as this is the original clapboard siding and I don't ever plan on replacing it!
    Even if the foam means it starts rotting?

    I also checked on a few of the foam products and haven't found any dealers in my area, but I may call them next week and see what they say.
    Google "pour foam".

    Tearing the siding off is a thought. I just wonder how much work/trouble it would be furring the windows and such out to account for sheating. Hmm... Siding in and of itself doesn't scare me one bit, as I used to be a siding sub on new construction for a few years. Problem is I've never messed with the clapboard much and I want to keep this original siding.

    Let me ask this, is there some wrap that I could possibly use in place of using sheeting? I know sheeting would be preferred, but.......

    If I pull the siding off, should I just install fiberglass batting? I know the sprays might be more efficient, but I am not easily convinced all of that type of stuff is really worth the added cost. I'm sure not paying someone $10k+/- to insulate my house. The other thing I worry about is getting this house too tight and causing issues. These old houses are designed to breathe.

    Thanks for the things to ponder....
    Yes, you could then use fiberglass, or cellulose... Would the savings, from not using foam, cover the extra hassle? Not sure.

    As for sheathing - house that old probably has left-in bracing for racking/sheer resistance, so it's not absolutely necessary. Probably ok with just housewrap. It's been there for awhile, right? And it's still fine?

    If you open up the walls & there's no bracing, though... I dunno.

    Mind you, if you don't add sheathing, you'll have to be extra-careful with flashing, because it's one less backup drainage plane. And must tape every seam, because it's also your air-seal, now. FG is useless if there's air movement, it's just a big air filter then.

    You're right that the old walls are designed to breathe - they work by a very different process than modern walls. The old walls let water in, but also let it out again; and they have plenty of airflow (drafts) to make sure things dry out, later. That's why it gets complicated when you insulate them. It's easy to cause a disaster. You stick insulation in there, now there's something that holds water if it gets damp.

    So your water-management details have to be tighter, and you have to seal up the drafts, to prevent moisture-laden air getting in & condensing inside the wall. But by doing that you're also making it harder for any moisture that does get in, to dry out... The worst outcome is when you try to compromise between new & old approaches. An insulated wall that leaks, doesn't last long.

    A lot to think about, for sure.
    Last edited by frenchie; 01-12-2009 at 05:55 AM.
    Master Plumber Mark:

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    it smells like......victory......

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    DIY Senior Member Master Brian's Avatar
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    You are correct, there is a lot to think about. The worst part is for every question, there are a dozen different answers!

    No, the foam is not good if it gets wet and the wood rots out. I do think, at least to some extent, that if I at least stay on top of the exterior maintenance, any rotting should be kept to a minimum. It would be one thing, if it sat and sat and sat in damp conditions for years, but, if you can catch the issue, that "should" buy some time. That theory probably works best when dealing with rain and such. The condensation is another thing all together and a real concern, because my windows ice up badly in the really cold weather!

    I have googled pour foam before, but will do it again. I know there are some DIY kits, but they just seem really, really expensive. My average utitlity bill is probably $250-$300, for this 1-1/2 story, 1900 sq ft house with about 700sq ft of unfinished basement. I know that is not good by any stretch compared to today's newer houses, but it is what it is on these old houses. In fact my previous house was 1300sq ft and 1-1/2 story and it cost me about $25 per month more for utilities! My point is, it would take 10+ years to justify spending ~$10k on having someone insulate the house correctly. I just am not certainit's worth that.

    I also know from experience, with watercraft, with two part foams, they do tend to get waterlogged over time. I suppose one solution which wouldn't provide excellent R value, would be to use 2" rigged foam panels, cut to size and inserted into the walls. With that, I would then leave a little "air chamber" as well throughout he outside of the wall, which would allow the wall to still breathe! Thoughts?

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    Extreme DIY Homeowner Scuba_Dave's Avatar
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    I went thru similar problems with my old house - 1905
    Luckily it had sheathing & tar paper
    The inside was a mess so I gutted room by room on the inside & insulated

    The problem I see with the rigid foam boards are they have to be tight
    If you have any gaps it will let air flow in
    That said any insulation is better then none, but better to do it right the 1st time. My kitchen was cold & drafty before, after it was nice & warm.
    I was heating with wood - open floor plan, so it cut down on the amount of wood I went thru

    Is your basement "warm" ? I had single pane windows & a door that did not shut right. New door, new windows, insulated the sill plate all the way around. Basement went from 45 the 1st year to now around 58-63 depending upon outside temps

    How old are your windows? As purchased our house had vinyl replacement windows, But they never took out the sash weights & insulated the cavities. I spent maybe $4500 on new windows, I have since saved that money in reduced heating costs. An added bonus is the house is much quieter
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