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Insulation for a thin wall

ajs | Posted in Energy, Heating & Insulation on September 29, 2008 06:58am

I want to insulate the walls in my house (southern New Hampshire, built in 1840, post and beam construction, wood sheathing with clapboards on the outside and plaster and lath on the inside) and the wall opening is only about 2″ deep. We have a similar situation at our church (balloon construction, built in 1896 with wood sheathing and cedar shingles on the outside and plaster and lath on the inside) where we want to insulate some of the office and meeting space and the wall opening is only 7/8″ deep.

I assume that the preferred insulation material would be foam so that a higher R value could be achieved. Does anybody have experience with insulating shallow walls like these either DIY or using an insulation company. If so, did you use foam, were you able to reliably fill such a shallow cavity, how did you get the insulation in, and how did the job turn out.

Thanks,

Al Smith

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Replies

  1. User avater
    xxPaulCPxx | Sep 29, 2008 10:10am | #1

    There is a slow cure pour in foam that might work.

    Rebuilding my home in Cypress, CA
    Also a CRX fanatic!

    I don't feel it's healthy to keep your faults bottled up inside me.

  2. DonK | Sep 29, 2008 12:43pm | #2

    No experience with walls that thin, but I would be interested in/concerned about the structural support it could provide, enough so to investigate it.

    Foam might work. It tends to get expensive, especially when used in small applications. Another option would be to build a new wall inside the old one to give you more space for insulation.

    Don K.

    EJG Homes    Renovations - New Construction - Rentals

    1. frenchy | Sep 29, 2008 04:51pm | #3

      DonK

       If that wall has stood up for 113 years and shows no sign of failure I suspect it will hold up longer.

      Edited 9/29/2008 9:52 am ET by frenchy

    2. User avater
      JDRHI | Sep 30, 2008 05:41pm | #8

      With post and beam construction, there are no structural issues with the partition walls.

      J. D. Reynolds

      Home Improvements

       

       

       

      1. frenchy | Sep 30, 2008 06:19pm | #9

        Jaybird,

         I don't believe this is an interior  partion wall since he is using insulation for thermal protection. 

        1. User avater
          jonblakemore | Sep 30, 2008 06:47pm | #10

          In a post and beam structure (you know about these, right?) the exterior wall is not really structural. You have wind loads to contend with, but no loads or any significance. 

          Jon Blakemore RappahannockINC.com Fredericksburg, VA

          1. frenchy | Oct 01, 2008 02:24am | #12

            Jon

             Gee! What's a post and beam <grin> 

              OK   Most exterior walls are structural. (mine are but then I'm wacko...)

        2. User avater
          JDRHI | Sep 30, 2008 06:53pm | #11

          Didn't mean interior partitions....meant the exterior, insulated walls.

          J. D. Reynolds

          Home Improvements

           

           

           

      2. DonK | Oct 01, 2008 04:15am | #13

        Hi Jon -

        I understand post and beam construction. My note to OP was as much related to the church with the balloon framing. I've worked on them before, but have never seen exterior structural walls of that thickness.

        Don K.

        EJG Homes   Renovations - New Construction - Rentals 

         

        1. ajs | Oct 01, 2008 05:54am | #15

          Don, I am the OP and I am also puzzled by the 3/4"-1" space between sheathing and lath at the church. The church building is arts and crafts style, built in 1896. It has stone walls typically up to about four feet, with a framed construction on top of that. The exterior has cedar shingles and a slate roof and the interior has plaster walls, oak floors, and stained oak for trim. In preparation for insulating the walls, we bored 8 test holes from the outside in different parts of the building and found that the space between sheathing and lath was about the same in each. It appears that the builders used double sheathing with a heavy duty gray paper, something like resin paper, between the sheathing layers. In the next day or two I will go into the attic and try to get a look down on the framing and see how they laid it out. Today I read the web site info for tiger foam and one or two other suppliers of DIY foam. in addition to spray nozzles they have a nozzle for filling up space in existing walls to be used with low expansion foam. I will call them tomorrow to find out if their foam is runny enough to work with 7/8 inch wall spaces and if so, what vertical and horizontal hole spacing they recommend.

          1. ajs | Oct 02, 2008 07:09am | #18

            I contacted Tiger foam tech support and was told that their slow rising foam should work with a wall opening as thin as 1 ". Compared with the regular spray foam, the slow rising foam has a retarder in the catalyst that delays the foaming action. The sprayed material stays lavalike until it settles into the nooks and crannies and then it expands over the next 90 seconds or so. The tech support person stressed the importance of agitating the tanks before using, particularly the "B" tank. It has both water soluble and oil soluble material that needs to be mixed well before using. Rolling the tank in the yard is an effective way to do this.
            He also stressed the importance of having the tanks warm enough. A warm-up in the hot tub or bath tub was suggested now that cooler weather is coming. The main challenge is to have all the wall access holes readily accessible because once you start to apply the foam, if you stop for more than about 45 seconds, the foam may begin to harden and you may have to change the nozzle. The following link to a fomofoam web site has a good description of how to fill walls with slow rising foam: http://www.fomofoam.com/Soundproofing.htm#ExistingIt suggests that if you have concerns about the foam filling a wall cavity, just get some clear plastic tubing, slip a foot or two of tubing over the nozzle, shove it through the access hole, and direct toward the bottom of the cavity. Both Tiger foam and Fomofoam are owned by the same parent company and sell the same product. The tanks are shipped by UPS freight and weigh about 115 pounds. The foam unit can be shipped to your home address or to a UPS office for pick-up

          2. PapaHeiser | Oct 02, 2008 07:59pm | #22

            I have a house that was built in the 1890's that has 2 x 4 construction for the outside walls, and I was initially thinking that the walls were only 2" thick (because I was looking from the outside through a hole where the siding had been ripped away) but I came to find out that the walls actually have a layer of plaster and lathe in the MIDDLE of the stud cavity. There are 2x2 cleats nailed on the inside of every stud cavity and there is plaster and lathe nailed to the cleats. So I now have vinyl siding on the outside, then the original wood dutch lap siding, 2" of airspace, a layer of plaster and lathe, another 2" airspace, and then drywall (originally plaster I'm sure, put replace by drywall by the previous home owner) I'm really scratching my head as to why this was done, so if anyone can tell me, I'd be appreciative. I had an insulator come in the look to give me an estimate to install polyurethane foam. He couldn't believe what he was seeing - said he'd never seem anything like it. Long story short, I was thinking I had thin walls like you, but after tearing off some drywall inside the house, I found out that I actually had 4" thick walls. I don't know, but maybe they used it to help stop air infiltration and create a dead air space so that the house is warmer? If so, it didn't work very well.

  3. DickRussell | Sep 30, 2008 02:58pm | #4

    I always wonder about how well insulating a really old building works with respect to moisture and mold/rot. Those old buildings typically leak air like sieves, and all that air movement quickly dries out the wind-driven rain that gets behind the siding and around windows that weren't flashed with the materials available today.

    If you put into the cavity something that impedes the ability of the wall to breathe (ie. leak air like a sieve), what will happen inside the cavity over time?

    I would think that closed cell foam would be best, since it would be a barrier to air infiltration and diffusion of moisture from either side. Still, I have to wonder about the wood sheathing absorbing the rain leaks.

    I'll watch for posts by those who have done old buildings and had good results over time.

    1. frenchy | Sep 30, 2008 03:30pm | #5

      DickRussell

        Wood is wood.. it really doesn't matter if it is todays OSB or yesterdays old growth pine.  If you get wood wet and keep it wet it will rot.. if it should remain dry  it won't. 

        They were as capable of building well made buildings back then as they are now. Witnessed by the number of survivors from that era..  

        Foam is actually more likely to prevent rot than any other insulation.. because foam can exclude moisture from entering the cavity in the first place where fiberglas or celluliose will allow water to enter and then retain it longer than it would have other wise.

        IN addition foam greatly strengthens a building. SIP's which are simply two sheets of OSB glued onto a block of foam is 200% stronger that the same wall made traditionally with 2x4's or 2x6's and sheathed in plywood and sheetrock. 

       Thus Foam structurally strengthens an old building and is capable of excluding moisture intrusion.  I fail to see a down side to the use of foam..  

      1. DickRussell | Sep 30, 2008 04:26pm | #6

        I was thinking more of the rain leaks that would wet the sheathing and outside faces of the studs, soaking into the wood. With the loss of exposed surface where the foam meets the inside of the sheathing and the studs, there would be only the outside of the sheathing exposed to drying. More modern construction, if properly done, has better flashing and a WRB to minimize the soaking of the wood.I guess it would depend on the particular old building in question.

        1. frenchy | Sep 30, 2008 04:41pm | #7

          DickRussell

           I'm thinking now of boat construction.. It's seldom unless worms or other organisms get to it that wood in direct exposure to water rots..

           What rots is usually the part exposed to air. 

           So if we exclude air from the back side of wood aren't we achieving the same thing? 

  4. User avater
    Jeff_Clarke | Oct 01, 2008 05:15am | #14

    Hi Al -

    Yes, I've done this professionally, although with a 2" cavity in between solid wythe brick masonry exterior wall and plaster/wood lath interior.

    We used Tripolymer foam - http://www.tripolymer.com/tripolymer/index.html - it worked great.  The foam was injected into holes drilled from the interior.

    Here is the building, a National Historic Landmark - http://en.wikipedia.org/wiki/Image:Joseph-henry-house.JPG

    View Image View Image

    This building, which houses the Council on the Humanities and the Society of Fellows at Princeton, has been picked up and relocated on the campus no less than three times - so this is it's fourth location.

    Jeff



    Edited 9/30/2008 10:32 pm ET by Jeff_Clarke

    1. ajs | Oct 01, 2008 06:27am | #16

      Hi Jeff,The Joseph Henry house looks like quite a place. The original part of our house ( 1840) was much simpler, 36 feet wide and 16 feet deep, two rooms over two rooms. The tripolymer foam looks like a quality product. On their web site, they say that a 1" minimum void is required for the efficient flow of the Tripolymer foam into all joints and corners. So it might work for my house, but probably not for the church. Do you know if the supplier makes it available for the DIY user?Thanks,Al

      1. User avater
        Jeff_Clarke | Oct 01, 2008 07:01pm | #17

        Almost sure they don't.

         

        Jeff

  5. bruce22 | Oct 02, 2008 03:21pm | #19

    Since your house has plank walls, there is no cavity to fill with insulation. I would strip the plaster and lath, install at least 2" hi-R foam board and rock right over that. That will give you a continuous layer of insulation and reduce air infiltration considerably.

     

    1. ajs | Oct 02, 2008 06:20pm | #20

      Your suggestion has a lot of advantages, but four years ago we re-wallpapered and my wife says that we are not about to touch it.

      1. User avater
        xxPaulCPxx | Oct 02, 2008 07:41pm | #21

        No problem, just put the foam board over the wallpaper!

         

        "What?  I didn't touch it!  Your wallpaper is perfectly safe under the insulation."

         

        ;)Rebuilding my home in Cypress, CAAlso a CRX fanatic!

        I don't feel it's healthy to keep your faults bottled up inside me.

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