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  1. #1
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    Default question about insulation inside closed walls

    Hello,

    I am new to TOH discussion boards. I hope to find lots more information here than can already be found in the magazine.

    I have many questions about insulation, but I'll start with just one for now. I have no insulation in the walls in my 1920's house. I am wanting to add it...one room (or two) at a time. I plan to do some from the inside of the house and some from the outside. I have one large room in the back of the house that I wanted to start with, since it is the coldest. It has textured paneling (no grooves) on the wall. The paneling was installed over existing wallpaper, which is over original solid wood walls. The paneling was installed sitting not behind the basesboards, but on top of them. So, 8 feet above that is a seam with a molding to cover the seam. My plan was to remove the molding covering the seam, then remove the top section of paneling. After that, I would drill the necessary holes into the solid wood walls and shoot the insulation down into the bays. I called Home Depot to get a cost on renting the machine and they said they would not recommend I do it that way because the insulation will settle in about 2 years and only 1/4 of the wall cavity would be insulated. Anyway, I'll address that later. My question is this. On TOH.com, there is a how-to video of Tom Silva showing this procedure, but from the exterior of the house. He does not give a reason for this, but I wanted to know why he blows in insulation from the bottom and the top of the wall? I was thinking it was because there might be a fire block in the wall, but he states that you can plug the top hole with a rag while you are blowing into the bottom hole so that the insulation doesn't come out the top hole. If there were a fire block, then surely the insulation wouldn't come out the top. Does anyone know why he goes from the top AND the bottom? Here is a link to the video.


    http://www.thisoldhouse.com/toh/vide...047052,00.html

  2. #2
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    Default Re: question about insulation inside closed walls

    Sophie... congrats on recognizing the need for insulating and tackling this yourself.

    I watched that video and it looked to me that the home was a two story. So the bottom hole may have been for the lower level and the top hole was for the upper level.

    The insulation contractors I've worked with use the two hole method for single level homes as well. Since they can't see inside the walls for any obstructions such as cross blocking .... they drill a hole at the midpoint of the wall to ensure a proper fill in the lower part. The filling from the upper hole ensures good fill from the midpoint to the top.

    Now you may try it from the top but you wouldn't know if there are obstructions inside the wall preventing good coverage lower down.

    Good luck.

  3. #3
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    Default Re: question about insulation inside closed walls

    DwarfWytch ... good point about the K&T.

  4. #4
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    Default Re: question about insulation inside closed walls

    Quote Originally Posted by canuk View Post
    Sophie... congrats on recognizing the need for insulating and tackling this yourself.

    I watched that video and it looked to me that the home was a two story. So the bottom hole may have been for the lower level and the top hole was for the upper level.

    The insulation contractors I've worked with use the two hole method for single level homes as well. Since they can't see inside the walls for any obstructions such as cross blocking .... they drill a hole at the midpoint of the wall to ensure a proper fill in the lower part. The filling from the upper hole ensures good fill from the midpoint to the top.

    Now you may try it from the top but you wouldn't know if there are obstructions inside the wall preventing good coverage lower down.

    Good luck.
    Good observation. I had not really noticed the house was 2 story. But, wouldn't there be some sort of blocking between the 1st & 2nd floors? I'm not completely aware of what is inside the walls of a 2 story house, but I would think there would be some 2x4s at the top of the studs that make up the 1st floor walls and which the 2nd floor studs sit on? If so, then how is it that the insulation was coming out of the top hole when he was blowing it in the bottom hole. You could see a little come out just before he stuffed the rag in there.

    It's true what you said about not knowing if there are any obstructions. But, I think it's safe to assume that I don't have any. Several years ago, my dad & I were doing some work there and it required us to take down the centermatch boards on one wall to shim it....and there were no obstructions like a fire block or anything. Now the room I'm wanting to start on was an addition to the house, but I wouldn't think they would have added that. Not to mention, my house was rewired and I don't remember there being any problem getting the cables down the walls.

    Quote Originally Posted by DwarfWytch View Post
    Sophie,

    Haven't seen the video and not sure if it was discussed, but if your electrical wiring is vintage (especially if it is Knob and Tube (K&T) you wouldn't want to fill those bays until it was replaced (and the old K&T disconnected). If you're in a rural area where electrification didn't occur until later you may find the wiring takes some interesting paths.

    Depending on the type of insulation, usually two or three holes per bay are used to assure the proper fill, and more importantly to avoid overfilling (not a good thing, especially with lath and plaster walls nor near window openings!) . As you explore additional resources you'll find that depending on the method, and the home's construction (for example near a pair or more of windows, etc. installed individually not mullioned together) you may actually have to drill three holes, or even four if there is a solid obstruction, pipe, brace, etc. across a stud bay to fully insulate the cavity and avoid cold spots.

    Did they demonstrate the use of a hole saw (on a drill) in the video? Saving the plugs for filling the wood holes might prove useful (and numbering them or something with a pencil) in case you later decide you want to expose the wood walls (matching grain, etc.).
    No, my house was rewired from the old knob & tubing before I purchased it. It was all still up in the attic, but it was abandoned. Since purchasing it, I had the entire house rewired about 4 years ago.

    I was planning on using the cellulose insulation. I don't have lath & plaster walls.

    Yes, the video shows him drilling the hole. He did not use a hole saw, he used a 1 1/8" spade bit.

  5. #5
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    Default Re: question about insulation inside closed walls

    Sophie... depends on when that house was built and the type of construction used.

    It may be ballooned framed in which the studs run continuous from the foundation to the upper story. Newer method is called platform framing which the studs only run from the floor to the ceiling of each level so in this case there would be an obstruction.

    That's good news your place has been rewired.

    Good luck.

  6. #6
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    Default Re: question about insulation inside closed walls

    DwarfWytch........

    ***! You've given me alot to think about. I guess I was hoping for a simple & straighforward solution to my problem. I keep telling myself to expect the worst when working on an old house.

    My lunch hour just ended, so I have to sign off. I will go back and read through your post again when I have a few minutes.
    Last edited by SophieC; 10-22-2007 at 01:33 PM. Reason: .

  7. #7
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    Default Re: question about insulation inside closed walls

    DwarfWytch.....

    OK....it seems smileys don't work the same way on this site that they do on TheCatSite.com. I am not upset or mad. There is no need to apologize. When I put that smiley, it was meant to be sort of a joke when I said I was looking for a simple & straighforward answer. I know that there usually is none when talking about old houses.

    To clear up the confusion, the house was rewired from the old K&T before I purchased it. But, after I purchased, I had the entire house rewired. I don't remember the electricians having any problems running the new cables down the walls. But, since I was at work while they were there, I'm not sure how it was done. It seems likely that they may have attached the new to the old from within the house and then pulled it up into the attic. Now that you mention those corner braces, I do remember then having a problem in one spot....and it was on a corner. I even stuck my hand up the hole to try and grab the cable. We could hear that it was "right there" but no one could grab it. They ended up running the cable under the house.

    I would be weary about using the low expanding foam in the wall cavities. The reason for this is that if in the future, I decided I need to run some wires or cables down the wall, then it wouldn't be possible, right?

    It's starting to sound like this may not be a good project to tackle. The last thing I want to do is start taking everything down to the studs. It almost seems that would be the only way to ensure proper fill....and at the point, it would be rolled insulation if I have the walls completely open. I also read in an article yesterday in Old House Interiors that blowing cellulose into an existing wall is not the best idea because of exactly what you mentioned.....you won't be guaranteed of full coverage and it will settle.....making all the effort worthless.

    Maybe just re-insulating the attic will make a difference.
    peace,
    Sophie

  8. #8
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    Default Re: question about insulation inside closed walls

    Quote Originally Posted by SophieC View Post

    It's starting to sound like this may not be a good project to tackle. The last thing I want to do is start taking everything down to the studs. It almost seems that would be the only way to ensure proper fill....and at the point, it would be rolled insulation if I have the walls completely open. I also read in an article yesterday in Old House Interiors that blowing cellulose into an existing wall is not the best idea because of exactly what you mentioned.....you won't be guaranteed of full coverage and it will settle.....making all the effort worthless.

    Maybe just re-insulating the attic will make a difference.
    Sophie ... you shouldn't be scared off insulating your home. It's a good thing that you would be doing for your comfort and energy savings. There would no need to tear down the walls as if done properly the blown in cellulose insulation will work fine for your retrofit.
    At the start of this thread you provided a link showing Tom Silva blowing in insulation and at this one http://www.thisoldhouse.com/toh/arti...9167-6,00.html you will notice some of his evaluations of insulation... note the cellulose.

    There can be confusing information and it can be discouraging ... don't be ... you're idea of insulating is a good one.

    Cheers.

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