New Shop - House Wrap or Not???

[Frank Aaberg]

Building new room INSIDE an existing pole building. The pole building is 30x45 and has house wrap. I will be putting the new room inside that will be approximately 18x26. Building (inside) in the far corner of this existing pole building, I will have the walls against the existing outside pole building with the wrap. Since the other two walls of the shop fall within the pole building (but not against the exterior walls of the pole building) is there any reason to use house wrap there? Thanks!

[Bob Riefer]

In my shop, I have some interior walls with conditioned space on one side and unconditioned space on the other (similar to your situation) and I used batts with the paper backing. My walls are OSB on both sides, so they may act as a vapor barrier potentially, but I'm unsure. This past year, I had a need to open up a portion of one of these walls to run an electrical line, and found the material to be in like-new, as-installed, condition after 10 years of service. I'm not saying this is the proper way necessarily, but thought a practical example may be useful.

[Dave Sabo]

Your location would be useful info for this discussion. There’s a section in your profile page to add it.

What works in Colorado isn’t so useful in South Florida.

Is your shop heated and cooled ?

[Jim Becker]

Frank, my post frame building went up yesterday and I did choose to put in house wrap. Part of that was because I was not sure what insulation method I was going to use when I specified the job. While I've now decided to move forward with closed cell spray foam, the house wrap isn't an issue, especially in the corners as it will help insure that the foam doesn't escape when first applied and it starts to expand. House wrap is relatively inexpensive, too.

FYI, most house wrap is mostly a wind barrier, so it's applicability isn't as affected by geography and it doesn't replace/displace using or not using a vapor barrier which can be geography dependent.

[Dave Sabo]

Frank, my post frame building went up yesterday and I did choose to put in house wrap. Part of that was because I was not sure what insulation method I was going to use when I specified the job. While I've now decided to move forward with closed cell spray foam, the house wrap isn't an issue, especially in the corners as it will help insure that the foam doesn't escape when first applied and it starts to expand. House wrap is relatively inexpensive, too.

FYI, most house wrap is mostly a wind barrier, so it's applicability isn't as affected by geography and it doesn't replace/displace using or not using a vapor barrier which can be geography dependent.

While you’re technically correct - the devil is in the details.

Some house wraps are / can be vapor barriers and specifically what’s used can make a difference. As does location. What works in the desert doesn’t do so well in northern New England and costal Carolina/GA has its own set of issues.


Practically speaking though, and with the little info we do know about this exercise - the answer is “no” there’s not a good reason for housewrap on the walls of an interior room.

[Jim Becker]

I missed the part about whether or not to do it on interior walls and I agree with Dave that "no" is a good answer. Only the envelope when used, IMHO.

[Bill Dufour]

If he lives in Alaska with deep permafrost the answer may be different. Will the mudsill ever get above 32 F?
BILL D

[Steve Rozmiarek]

Echoing the location and use details needed. In 4 season climates where part of the building is heated, part not, there are few reasons to use house wrap on interior spaces.

[Rob Sack]

Frank, my post frame building went up yesterday and I did choose to put in house wrap. Part of that was because I was not sure what insulation method I was going to use when I specified the job. While I've now decided to move forward with closed cell spray foam, the house wrap isn't an issue, especially in the corners as it will help insure that the foam doesn't escape when first applied and it starts to expand. House wrap is relatively inexpensive, too.

FYI, most house wrap is mostly a wind barrier, so it's applicability isn't as affected by geography and it doesn't replace/displace using or not using a vapor barrier which can be geography dependent.

According to the folks at DuPont, when I used Tyvek some 30 years ago under my exterior siding, they claimed that when installed correctly, it was superior to building paper or building felt in vapor transmission in one direction and allowed vapor transmission in the other direction. When installed with the "Tyvek" printing facing out, it acts as a vapor barrier preventing outside moisture from entering the building. At the same time, it allows any vapor in the walls to escape.

[Jim Becker]

That's correct relative to my understanding, too, Rob, and allowing moisture "in" the wall to escape outside is important to reduce the risk of mold and other bad effects that can happen.

[Rob Luter]

I would wrap and insulate the interior shop walls just as if they were exterior walls. This assumes that the interior of the shop will be tempered (heated/cooled) space and the remainder of the pole building will be untempered.

[Steve Rozmiarek]

According to the folks at DuPont, when I used Tyvek some 30 years ago under my exterior siding, they claimed that when installed correctly, it was superior to building paper or building felt in vapor transmission in one direction and allowed vapor transmission in the other direction. When installed with the "Tyvek" printing facing out, it acts as a vapor barrier preventing outside moisture from entering the building. At the same time, it allows any vapor in the walls to escape.

Tyvek is interesting, if you cover a lumber pile with it for example, it won't keep rain out. If it gets stressed and pulls the weave apart, it lets air through, so it's neither waterproof or air proof. However, on a vertical surface it sheds water really well and stops air movement within the walls. A useful tool if used properly.

[Bob Falk]

Tyvek, and similar products, are air flow and water intrusion barriers. Assuming there is no wind or rain inside the pole building, it seems unnecessary.

[Frank Aaberg]

I'm back after being in the woods where the pole building is and the Internet isn't! Never expected to come back to do many answers. I appreciate everyone's input.

My bad that I didn't include location. Late, but I'll throw it out ... Northeast Wisconsin. Very cold in winter (-20) to hot (90) and VERY humid in the summer.

Thanks again!

[Rob Luter]

In that location I'd wrap it. Again, this assumes the shop area will be heated/cooled and the remainder of the pole building will not. If this is the case, the temperature differential alone will impact RH differential between the two spaces.