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  1. #1
    Join Date
    Mar 2009
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    5

    Question Blown-in cellulose and mass confusion - please help me!

    I have 1918 United Grain Growers catalog home, located near Saskatoon, Canada. -40c in the winter is fairly normal. The house has no insulation in the walls - zip, zero, zilch. It's built like a tank - plaster over wood lathe over 1x6 shiplap over the studs, a hollow cavity where the insulation would normally go, and some nice tight siding. But it's chilly.

    The plaster and lath has been removed from the 2 exterior walls - they are stripped down to the shiplap. The original plan was to remove the shiplap, install fibreglass batts, vapor barrier, and drywall. But after trying to remove a few pieces of the shiplap, I'm (a) nervous about doing so, as it seems to provide some pretty solid structure to the walls, and (b) really reluctant to undergo this massive task - this stuff isn't coming off easily, which reassures me that it is meant to be there.

    Great for my rock solid house... not so much for my gas bill.

    And then I had a thought... now that it's pretty easy to drill into the wall cavity, and I know that the cavity is completely empty, what about just sealing up any gaps and blowing loose-fill cellulose insulation in?

    I'd be heading to Home Depot first thing tomorrow and renting the blower, but I want someone to set my mind at ease first. The more I read, the more conflicting opinions I discover, and the more nervous I get. Blowing in cellulose would mean that I would have the following layers, from the outside in:

    exterior siding
    loose-fill cellulose
    1x6 shiplap
    gyproc
    paint

    The words 'vapor barrier' do not appear in that list. Should they? I read that cellulose doesn't need a vapor barrier, and then I read that it does. Would it be wise to put a vapor barrier between the shiplap and the gyproc, or is that unnecessary, or is it stupid?. I live in a climate that is very cold in winter, not too bad in the summer, and the air is pretty dry most of the time. I read so many conflicting things from so many parts of the world that I don't know how to tell what is right for my house and climate!

    Thanks so much for setting my mind at ease...
    Cheers
    Tracy

  2. #2
    Join Date
    May 2009
    Location
    Elyria, Oh.
    Posts
    245

    Default Re: Blown-in cellulose and mass confusion - please help me!

    Drill the holes, put the blower hose and go. It is impracticle and impossible to blow cellulose into the wall and add a vapor barrier also. It is not the ideal situation but houses built before the 1970s had virtually no insulation because gas was cheap. Homeowners just turned up the heat. I've done this several times and it is easy to do. You need two people, one to feed the machine and one to direct the hose. Home Depot used to have a deal if you bought so many bales of insulation you got the machine for free.

  3. #3
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Blown-in cellulose and mass confusion - please help me!

    Now there's a blast from the past --- along with the old Eaton's and Canadaian Alladin mail order homes.
    Though those U.G.G homes were more in Saskatchewan I believe since that's where U.G.G was formed ---- Indian Head if I recal correctly.

    Anyways ........

    Typically for us folks on the prairies we generally would always consider a vapour barrier installed in any home.

    With cellulose , fiber glass , rock wool and even 1/2 pound open cell spray foam --- building code would require an additional vapour barrier installed with any new construction or renovation in our climate .

    However, in a retrofit application it is allowed and there wouldn't be any need to require a vapour barrier.

    This works without the vapour barrier as long as you seal the wall as air tight as you can make it.

    If you were to take down the walls then it would be best to apply a vapour barrier.

    The existing walls probably have several coats of paint with some being at least 2 coats of oil based paint --- or even some layers of vinyl wall paper.

    The many coats of paint ( especially the oil based ) combined with the plaster itself acts as a vapour retarder. While the walls will allow some vapour to pass through the process of diffusion, it will slow and limit the diffusion . Whereas if you were to out up 6 mil poly vapour barrier this material does not allow vapour to pass through ----- hence the difference between retarder and barrier.


    The main concern is air infiltration from the indoor space into the walls that will create moisture issues --- regardless what type of insulation.


    If you aren't taking down the walls and are simply going to blow in the insulation just make sure it's dense packed.

    just some thoughts.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  4. #4
    Join Date
    Mar 2009
    Posts
    5

    Red face Re: Blown-in cellulose and mass confusion - please help me!

    Thanks guys! I guess I need to be more specific.

    The lath and plaster are already gone on those two walls - it is down to the shiplap. I am going to seal the gaps and cut hole in the shiplap and blow the insulation behind.

    I guess what I want to make sure is that I need a vapor barrier OVER the shiplap, i.e. between the shiplap and the gyproc I will be covering it with. It is my understanding that I do... but I haven't been able to find a specific example of this. I guess what I need to know is... is there any circumstance under which this might be a BAD idea? It would be poly sandwiched between shiplap and gyproc, not much space in between for air flow. Is there any danger of moisture building up in between and damaging the wall?

    A second scenario - what if I put a layer of pink foam board over the shiplap, i.e. between the shiplap and the gyproc. If I sealed all the seams between the foam boards, do I need a vapor barrier then?

    Thanks for any clarification you may be able to provide!

  5. #5
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Blown-in cellulose and mass confusion - please help me!

    Quote Originally Posted by skimmer View Post
    Thanks guys! I guess I need to be more specific.

    The lath and plaster are already gone on those two walls - it is down to the shiplap. I am going to seal the gaps and cut hole in the shiplap and blow the insulation behind.

    I guess what I want to make sure is that I need a vapor barrier OVER the shiplap, i.e. between the shiplap and the gyproc I will be covering it with. It is my understanding that I do... but I haven't been able to find a specific example of this. I guess what I need to know is... is there any circumstance under which this might be a BAD idea? It would be poly sandwiched between shiplap and gyproc, not much space in between for air flow. Is there any danger of moisture building up in between and damaging the wall?

    A second scenario - what if I put a layer of pink foam board over the shiplap, i.e. between the shiplap and the gyproc. If I sealed all the seams between the foam boards, do I need a vapor barrier then?

    Thanks for any clarification you may be able to provide!
    Your second scenerio would be ideal and you wouldn't require any vapour barrier.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  6. #6
    Join Date
    Mar 2009
    Posts
    5

    Thumbs up Re: Blown-in cellulose and mass confusion - please help me!

    Thanks Canuk!
    Just one last question... I wouldn't need a barrier in the second scenario, even WITH blown cellulose behind the shiplap? Like the foam board all sealed up is enough of a barrier?
    Awesome, thanks so much for your patience

  7. #7
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Blown-in cellulose and mass confusion - please help me!

    Quote Originally Posted by skimmer View Post
    Thanks Canuk!
    Just one last question... I wouldn't need a barrier in the second scenario, even WITH blown cellulose behind the shiplap? Like the foam board all sealed up is enough of a barrier?
    Awesome, thanks so much for your patience
    You got it.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  8. #8
    Join Date
    Mar 2009
    Posts
    5

    Smile Re: Blown-in cellulose and mass confusion - please help me!

    Brilliant. Thanks so much

  9. #9
    Join Date
    Feb 2010
    Location
    Eastern MA
    Posts
    75

    Default Re: Blown-in cellulose and mass confusion - please help me!

    Did you say -40C? Go with closed cell foam for the higher R-value. If you are stuck on cellulose, have it done professionally by someone who can do dense pack. Can't be done with a Home Depot blower. Dense pack is done either in a spray applied application or inserting the blowing tube in the wall. It is truly dense and will not fall out of an opened wall. You probably should have a vapor barrier in your climate. I would use vapor barrier paint. Don't forget to seal all the cracks, such as where the floor and walls meet.

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