House wrap after siding is up

[Cbrauer]

Our post frame building has been built, and in 50/50 hindsight, I realized I wish I had asked the contractors to install house wrap. We live in Oregon in a wind corridor (our wind even has its own name), and it seems like wrap would help limit air infiltration. We plan on insulating and putting up walls once we fix a few other problems. Eventually the whole building will be temp controlled.

I really don't feel inclined to remove the siding, wrap, and replace it. But I'm wondering if it would be worth putting tyvek up from the inside, stapled to the girts / posts and seam taped. Then follow with insulation. It seems better than nothing and a lot less hassle than taking the siding down.

We do have one shear wall that has plywood behind the metal siding, nothing in between. If we wanted to wrap that wall, we'd have to remove the siding to put the wrap between the metal/plywood. Anyone feel that it's important enough to add that barrier that we should do it? Or is plywood in direct contact w/ the metal siding not that big of a deal.

Thanks!

 

[u2slow]

Metal sweats, so it should have at least tar-paper behind it. My whole shop is wrapped in double layer tar-paper before the metal roof and siding went on. (Per code minimum in 2013.)

Also on this west/wet coast.... Poly VB on the inside of your stud walls before drywall.

 

[FredWanaker]

The wrap manages moisture also. Depending where you are in Oregon you might be able to install a vapor barrier on the inside walls before the drywall goes up, but you would want to check with the local insulation companies, or building dept to see which side the vapor barrier goes on there. Oregon is kind of a weird climate. Maybe reading this might help, there is also a map with climate zones on it (these are not the same zones as plant climate zones): https://insulationinstitute.org/im-...idance-2/moisture-management/vapor-retarders/

 

[Cbrauer]

Will definitely be installing vapor barrier on the interior side of the insulation prior to walls. Damp is a real problem here, we live in rain and fog soup for the better part of the year, but the summers are nice and dry. We'll have a mini-split with cooling capabilities, but 90% of the time we'll be running heat, so my understanding is vapor barrier between the walls and insulation will help.

I guess I will try to make my peace with taking the shear will siding down to wrap, at least. I imagine that moisture buildup between the plywood and metal is inevitable and not good for the long haul.

 

[u2slow]

The wrap manages moisture also.

I would be careful with housewrap (tyvek) *and* poly VB in our cool/damp climate. Moisture ingress can exceed the venting ability and walls mold/rot. I felt traditional tar-paper was a "less tight" and why I went with it.

 

[billconner]

House wrap manages water, not moisture. It's quite permeable.

If you're heating, you want a vapor barrier inside insulation

OR

at least inside enough insulation that it will stay above dewpoint. I like simple and proven and tolerance of less than perfect workmanship, so prefer poly inside. Many would say spray foam, which will replace housewrap in terms of keeping water and wind out, and will stop condensation in the wall if thick enough - in the 2" neighborhood. Good foam contractor, it can work. Rockwool or fibreglass or cellulose or more foam between inner wall and foam. If not foam, inner wall should remain permeable so it can dry in - drywall and plain latex or equal.

 

[Rc_Guy]

spray foam from the inside.

 

[FredWanaker]

My understanding is in western Oregon the barrier, if any as it may be better to let the wall breathe, goes on the outside. In the very early morning the sun's heat is driving more moisture into the air but the inside the wall is still cold after the night cold has soaked part way into the insulation and wall. The outside moisture needs to be stopped from getting into the wall, or allow the wall to breathe and not collect water. In early night it is cooler outside and the wall is warmer so moisture doesn't condense, so there is no need for a barrier.

Colder Eastern Oregon the barrier goes on the inside because inside humidity is higher than outside and it would condense within the cold wall in winter, so the goal is to stop that inside humidity from getting into the wall.

That is also what the link I posted indicated.

spray foam from the inside. (closed cell) works too as the last post indicated.

 

[Dakotadadv8]

Tar paper over treated plywood works well.

 

[u2slow]

House wrap manages water, not moisture. It's quite permeable.

That permeability is a double-edge sword. Yes, it keeps liquid water out. But vapour that condenses to water inside the wall (or direct water leakage) may never get warm enough again to escape.

It's a standard problem in coastal BC... I suspect WA and OR have similar climate.

 

[FredWanaker]

House wrap manages water, not moisture. It's quite permeable.

"mois-ture": water or other liquid diffused in a small quantity as vapor, within a solid, or condensed on a surface.

Wrap is meant to be permeable to the vapor, but hold condensed water back. That way any water that gets past it can breathe back out when it evaporates. By allowing that it manages the overall moisture content within the wall, which includes condensed water, and water that may have soaked into the wood. If I said it manages water, someone would water trapped within can't get out unless it is in vapor form. You folks are brutal.

 

[egdede]

When you say shear wall siding, that would mean nailed on 4" schedule on the perimeter in my jurisdiction. If nailed with ring shank nails it might hard to remove....

 

[rayra]

At this point you’ll need to spend big and seal the structure with spray foam.

 

[Uncle murph]

Our post frame building has been built, and in 50/50 hindsight, I realized I wish I had asked the contractors to install house wrap. We live in Oregon in a wind corridor (our wind even has its own name), and it seems like wrap would help limit air infiltration. We plan on insulating and putting up walls once we fix a few other problems. Eventually the whole building will be temp controlled.

I really don't feel inclined to remove the siding, wrap, and replace it. But I'm wondering if it would be worth putting tyvek up from the inside, stapled to the girts / posts and seam taped. Then follow with insulation. It seems better than nothing and a lot less hassle than taking the siding down.

We do have one shear wall that has plywood behind the metal siding, nothing in between. If we wanted to wrap that wall, we'd have to remove the siding to put the wrap between the metal/plywood. Anyone feel that it's important enough to add that barrier that we should do it? Or is plywood in direct contact w/ the metal siding not that big of a deal.

Thanks!

On the inside?Really really bad idea,it certainly helps when correctly installed on the OUTSIDE,but hardly a disaster to proceed with out it.Do a nice job insulating and finishing the inside and you will never miss it.

 

[Miss the Pontiacs]

One thing I would do is ever hirer these siding people to do any other work for me. They should have suggested the use of wrap to begin with. Or are we missing something?

 

[CraigStu]

I am with Uncle, I see no reason to even consider wrap now. I know that wrap is pretty much standard but think back. How many places in your structure would actually leak air? Heck wrap may do more to protect the sheathing before the siding is installed (waiting on the siding subcontractor) than it does in the completed structure.