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I'm building a tiny house and it will have metal siding. My dad has worked a lot of construction and says he's never installed a house wrap for a metal building in his life. Most info I can find online says if it's climate controlled it needs wrapped. Just wondering how important it is when it comes to metal siding?

Also, I may cut it close when I get to the tops of the walls, I'm planning to use the rest of the #15 asphalt felt I used on the roof to finish the job if I run out so I don't have to buy another roll. Is this a good idea?

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    Is this tiny house going to be moved ever? Or is it being built in place ? – Criggie Mar 13 at 10:39
  • Tiny as in, not very big, or tiny as in, could appear on "Tiny Houses" on HGTV? – Joe Mar 13 at 14:04
  • @Joe with 25 questions, I'm surprised we don't have a tag tiny-house. – SQB Mar 13 at 15:14
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    @joe I haven't added a tag before but my state defines a tiny house as a mobile or fixed structure from 100-400 sf. i tried to add that we will see if it works, – Ed Beal Mar 13 at 15:50
  • Makes sense, you just have to add it to the question now :) – Joe Mar 13 at 15:59
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I don’t see a problem with felt for a portion as it was used for years, I believe a wrap is a good idea as it will increase the energy efficiency and keep the condensation from the metal off the sheathing. If you use insulation under the metal as used in many roofs you probably would not need a wrap but it would still be a good idea.

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    I agree. Felt is just fine. The reality is that felt is probably better suited for metal in that it should not absorb. The drawback is that it can get brittle and it sometimes rips during install. – DMoore Mar 13 at 3:27
  • I did not think of brittle but over the years it will get brittle, if the small house is on a trailer this may be more of a concern.+ – Ed Beal Mar 13 at 13:38
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While I don't doubt that your father 'never installed a house wrap for a metal building in his life' I have to wonder how many of them were residences? Buildings with walls that trap moisture or where higher efficiency insulation is often needed? Bare and exposed insulation on the inside doesn't count.

Wrap is about what is INSIDE the wrap, not what is OUTSIDE the wrap. Tyvek lets moisture out while not letting air in or moisture in. Tar paper was the old school solution but it blocks air and moisture in both directions. Tyvek or other similar modern building is needed for insulated walls with poor circulation, metal or no metal.

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  • Metal also traps moisture and stops airflow in both directions so keeping the condensed moisture off the sheathing is important to prevent it from rotting. – Ed Beal Mar 14 at 13:53
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I don't see what the issue would be with the Tyvek (or any other) house wrap. When my renovations were done, much of the brick was removed & replaced with OSB+Foam Board+ House Wrap + Hardiplank (cement board). I don't see why the metal siding would any different from the cement board in so far as using a house wrap.

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    Metal condenses moisture on the underside in cold weather if no wrap or felt was used the sheathing would not last long especially with metal. – Ed Beal Mar 14 at 13:50
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Also in this case, a reliable way to get all necessary information concerning possible moisture, insulation and mold problems is to input each material in the layer fields on the professional Ubakus website, which is free for private use. Each layer can be switched on/off with a single mouse click to immediately see the difference.

Another important aspect is a good grounding of all metal parts in order to avoid dangerous voltages resulting from the electric installations or static charges. The mobile telephone/ router/ smart home signals may be affected, depending on the windows.

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  • It would be good to indicate if you've got an association with that web site or not. No problem if you do, so long as you issue that disclaimer. – FreeMan Mar 13 at 19:44
  • @FreeMan I do not have any association with that web site, I do not benefit/profit in any way from my recommendation of that site. It is just by far the most professional and sophisticated site to calculate and visualize the relevant insulation parameters that I have found up to now. For DIY the free access seems to be ideal. But I can't tell anything about the commercial option since I do not have access to it. – xeeka Mar 13 at 20:19

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