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  1. #1
    Join Date
    Mar 2005
    Location
    Illinois
    Posts
    138

    Default Vinyl siding - what vapor barrier to use?

    It's been about 7 years or so since I've installed any quantity of vinyl siding...7 years ago we used Tyvek or Barricade as a vapor/moisture barrier. More recently I've installed quite a bit of cedar siding and under that we use Tyvek as well.

    This summer I'm building a three season room on my house and I'll vinyl side it to match the siding on the existing house. Over the years I've become kind of anti-Tyvek as a moisture barrier, especially with the thought of vinyl siding as an exterior.

    My plan, unless it seems to be a poor choice for some reason, is to use either 15 or 30 lb felt as my moisture/vapor barrier behind the vinyl siding. I've never done this but it seems to me this would be a much better alternative to Tyvek.

    Any thoughts?

  2. #2
    Join Date
    Jun 2004
    Location
    Des Moines, Iowa
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    3,866

    Default Re: Vinyl siding - what vapor barrier to use?

    Quote Originally Posted by Stayfair

    This summer I'm building a three season room on my house and I'll vinyl side it to match the siding on the existing house. Over the years I've become kind of anti-Tyvek as a moisture barrier, especially with the thought of vinyl siding as an exterior.

    My plan, unless it seems to be a poor choice for some reason, is to use either 15 or 30 lb felt as my moisture/vapor barrier behind the vinyl siding. I've never done this but it seems to me this would be a much better alternative to Tyvek.

    Any thoughts?

    Stayfair

    Tyvek is a poor choice to use as a moisture barrier, it was not designed to be used as such. It is an air barrier.
    Vinyl has the potential to get very wet behind it, as it does every time it rains. When you use a paper to keep out the water, then you drive 5000 little holes in it, then you are suprised when down the road you have problems with moisture in to your wall cavit, or the next owner does, why the suprise?

    Instead use the fanfold foam and overlap it at the seems. At least you have a foam gasket around each nail

    Mark

  3. #3
    Join Date
    Jun 2004
    Location
    Little River, SC
    Posts
    1,234

    Default Re: Vinyl siding - what vapor barrier to use?

    I have been using 2 ply grade D jumbo tex weather barrier for the last 3 years. So far it has been doing great.

    I do quite a bit of tear offs with our projects & I see all kinds of weather barriers. Most commen is tar paper. The main thing I see with this is it being very brittle. Over time it looses its strength & thoughness. Why I don't know, but that is what I have been seeing.

  4. #4
    Join Date
    Mar 2005
    Location
    Illinois
    Posts
    138

    Default Re: Vinyl siding - what vapor barrier to use?

    Quote Originally Posted by Mark Parlee
    Stayfair

    Tyvek is a poor choice to use as a moisture barrier, it was not designed to be used as such. It is an air barrier.
    Mark
    Thanks for the replies guys...

    Mark, looking at Tyvek's web site it clearly states that it is a moisture/water and air barrier. I doubt it's effectiveness and that's the reason for my thread, but it doesn't seem like it was designed just for air infiltration.

    I'd like to look at that 2 ply grade D jumbo tex, I've never heard of it before. Any ideas on the cost?

    Any other ideas besides the foam (which I'm considering anyway just for a little added R-value across the plywood exterior) or tar paper?

    Tom

  5. #5
    Join Date
    Jun 2004
    Location
    Little River, SC
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    1,234

    Default Re: Vinyl siding - what vapor barrier to use?

    Quote Originally Posted by Stayfair
    I'd like to look at that 2 ply grade D jumbo tex, I've never heard of it before. Any ideas on the cost?
    Tom

    For the last 2 years is was $10.95 per 240sq ft roll. In the last 3 months the price has doubled. It is currently $21/ 240sq ft roll. Available at Home Depot & Lowes as well as most major lumber yards.

    There is a product made by Pactive called green guard rain drop. It has ribs in it, kinda like the home slicker product by benjamin obdayke. The problem is finding it locally. Most places carry tyvek or typar. They won't carry a similar product. What's the point of stocking 3 of the same thing is the reasoning you will get. I have never used it so I cannot speak on its effectiveness.

    I have used fan fold many times. It is a good product. The R value on 1/4" is 1.5.

  6. #6
    Join Date
    Jun 2004
    Location
    Des Moines, Iowa
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    3,866

    Default Re: Vinyl siding - what vapor barrier to use?

    Tom

    I stand corrected. I disagree with the claim as to moisture barrier. I have seen results of testing done, I believe an article in JLC addressed this as to the breakdown of the various housewraps and the causation of their failure. It has been my experiance when removing siding, vinyl or otherwise, the housewrap is in somewhat of a deteroraiting state. Tyvek is usally very brittle, nothing like what comes off a brand new roll.
    My choice now for building paper is Dow weathermate plus, and as I stated before fan fold under vinyl due to what I said about the gasketing effect around the nail

    Mark

  7. #7
    Join Date
    Mar 2005
    Location
    Illinois
    Posts
    138

    Default Re: Vinyl siding - what vapor barrier to use?

    Carl,

    Is that 2 ply grade D jumbo tex similar to standard snow and ice shield used on roofs? It sounds like a very similar product although the snow and ice shield seems more expensive (I'm not sure the sq footages are the same in the rolls though).

    Tom

  8. #8
    Join Date
    Jun 2004
    Location
    Little River, SC
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    1,234

    Default Re: Vinyl siding - what vapor barrier to use?

    No, it's not the self sticking stuff. This is more similar to felt. Not as heavy & has a resin in it which makes your fingers sticky after handeling it w/o gloves. Much like felt does. Try lugging a roll of 15# felt on to scaffolding, holding it & then staple it! Not very easy. I will email you a photo of our current job with the 2 ply on it.

  9. #9
    Join Date
    Jul 2004
    Location
    NOLA
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    4,186

    Default Re: Vinyl siding - what vapor barrier to use?


  10. #10
    Join Date
    Jun 2004
    Location
    Central Illinois
    Posts
    4

    Default Re: Vinyl siding - what vapor barrier to use?

    Here's a link that has been around this forum a few times:

    http://www.umass.edu/bmatwt/publicat..._barriers.html

    This is another one of those ongoing debates about which material is better. Better to have the viewpoint of someone other than the manuf. Even better to have the viewpoints of professionals that have used the material in the field - such as the people in this forum.

    I use Tyvek but I would say that most failures are due to improper installation.
    ~ Don R.

  11. #11
    Join Date
    Aug 2004
    Location
    Watertown, NY (NorthernNY)
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    1,111

    Default Re: Vinyl siding - what vapor barrier to use?

    We have resided many homes with vinyl and always use fanfold or insulation board behind it. Working on a tract development were the GC provided 15# felt as vapor/wind barrier, we noticed that our siding was oilcanning. After checking our work for proper nailing, overlap etc. I came to the conclusion that the felt paper was heating up the siding from the back side and causing the ripple. I don't know that that is true or not but we have sinced refused to use felt behind vinyl and have not had that problem since. The best protection that I know is to properly flash all your accessories to bring any moisture back to the weep holes in the siding. The JLC feild guide has excellent advice on this.

  12. #12
    Join Date
    Jun 2004
    Location
    North Carolina
    Posts
    450

    Default Re: Vinyl siding - what vapor barrier to use?

    I don't want to get involved in another Tyvek debate. I think I've been clear inthe past on this. Mark is right. Tyvek is not a moisture barrier. If they are now saying that it is, it must be for marekting purposes only and they must have figured out another legal way to weasle out of any claims of damage by perhaps redefining what THEY mean by a barrier to moisture. It might be a barrier to mositure (indirectly), but it is not a "moisture barrier" as we know it. It is also redundant as an air barrier if you use plywood or OSB sheathing. Why not just seal the joints and you have a perfect air barrier. Instead of taping the tyvek joints , tape the plywood joints (or caulk them). I honestly can't find any redeeming value of tyvek on a house. It makes great mailing envelopes and I like my tyvek jacket. But if all I am going to use for wrap is Tyvek, I just as soon save the money.

    The history of Tyvek is a great study in Marketing.

    glenn

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