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House Wrap--Perforated or not?

17 years ago

Sorry if this is an elementary question to many; we're building a home for the first time and are just testing the waters in many areas.

From the research I have done on house wrap, I was very much against perforated house wrap. However, I have now recieved conflicting information from our designer/supplier at the lumber yard. He feels non-perforated wrap won't allow the house to breathe. I asked him to please just order me some Tyvek anyway! But I did want to check here to make sure I am correct in this. The wrap he specified for our materials list is much less expensive than Tyvek, and we all hate to spend money unnecessarily.

Comments (6)

  • 17 years ago

    Your supplier is confused or dishonest. Perforated wrap is usually not even waterproof although it can pass the 10 minute test just fine. Tyvek is one of the most vapor permeable wraps available (this is what he means by the "breathing") so that is not a relevant issue.

    You did the right thing to order Tyvek. This is not the place to buy the cheap stuff. Did the wrap he recommended have the store name on it?

    Check out the installation instructions carefully. It is often just thrown up with a lot of unnecessary staples and cuts and no tape at the overlaps so it often doesn't act as a very good air barrier or weather barrier. But it's the best wrap you can buy.

  • 17 years ago

    Ditto.

    When I use housewrap at all, I prefer Typar as it easier to handle and its UV rating allows for up to 12 months exposure vs. 4 months for Tyvek.

    Here is a link that might be useful: Making Sense of Housewraps

  • 17 years ago

    "He feels non-perforated wrap won't allow the house to breathe."

    Houses don't need to breathe. Unless the house is less than .25 air changes per hour, you do not have to introduce make up air. It takes a lot of detail work to reach this level of air tightness.

    Houses should be built tight, and ventilated right.
    'Breathing' houses are leaky houses that breathe through cracks in walls, ceilings and bring in dust, insulation particles, and humidity.
    the only way to determine the tightness of a structure is to test it. this is usually done with blower doors to determine air changes per hour.

    That said...in my hot humid climate we often use foil faced closed cell insulation boards to the exterior wall.
    using a house wrap over this install reduces the R-value
    of the sheathing board. When all seams are taped, all holes are sealed this is our vapor barrier to the exterior.
    hot humid climates have this vapor barrier location, it changes with different climates.
    in homes with brick exterior we use the foil faced boards,
    some builder's insist on housewrap, so it is a chosen
    battle to ok the install next to the studs with foil sheathing boards over the housewrap. costs the home owner
    more, and labor to install, but R-value of sheathing is not devalued, and with R-15 in a 2x4 wall..with foil/foam sheathing..is R-20+ also the foam to the exterior of studs reduces thermal bridging..but that is off topic.

    I would discuss this more with this person.
    If they are not informed about the use of housewraps,
    permability and install you may have to eudcate yourself
    and then them and make sure the folks actually doing the install have the best info.

    best of luck.

  • 17 years ago

    Did you know that Typar was invented by DuPont when it invented Tyvek? Both are spunbonded non-perforated polyolefin but one is polypropylene and the other is polyethylene. DuPont sold Typar in the US but still controls the name in Europe. It has a lower higher rating but greater resistance to surfactants.

  • 17 years ago

    Did you know that Typar was invented by DuPont when it invented Tyvek?

    I probably did at one point. But with age, my brain has become leakier than perforated housewrap.

  • 17 years ago

    I actually did do some reading on Typar several weeks ago, and at that time I was leaning more towards Typar than Tyvek for the reasons mentioned, namely the UV resistance and the sturdiness against surfactants. I know it is also much thicker, but I didn't know if that was good or bad. It is technically much less permeable than Tyvek, but supposedly they say they are in the "optimal range" for balance between letting moisture out and keeping moisture out.

    We're in a cold climate (Minnesota), so I do think we have more interior condensation issues than some climates because of the inside/outside temperature difference in the winter. I think I will change my order to Typar after the reassurance of this thread.

    Luckily, we have a fantastic GC who is precise and thorough in his work, so I know installation will be well done in terms of lapping, tape, etc., evening if the well-meaning but misinformed guy at the lumber yard has no idea what he is talking about. This, friends, is why it pays to do your research :)