Vapor problem with Zip wall?

[shinnlinger]

Hi,

I hung conventional 2x4/zip wall walls on my timber frame a few years ago and time and money has prevented me from getting it done.  Today I went to plug away on the upstairs (I live downstairs) but when I pulled the insulation back to drill holes for wiring I noticed that a significant amount of moisture had been trapped between the inner surface of the zip wall and the pink stuff


Concerning to say the least.  The plan is to put 2 layers of 2 inch polyisocyinate foam continuously over the studs(4 inches) on the inside, foaming/not stacking the seams , strapping it and then hang drywall off the strapping.  That will create a significant vapor barrier but trapping moisture that makes it thru in the stud portion is obviously not a good thing.

I have had a fan blowing on it for several hours and it is drying out and the problem will be lessened significantly when the space gets heated and the interior foam is installed but I wonder if I should put a collar on a drill bit and drill the the zip wall as many places as a can to allow moisture to escape.  I have B&B hung on the outside.

I have an email into JM Huber.  This might just be what happens when you wait two years to finish an unheated space in winter while you live below it and moist air condenses on a cold wall, but interested in your suggestions/solutions before I bury it all back up.

Thanks.

Dave

[Jay C. White Cloud]

Hi Dave,

I am so terribly sorry!!!

I see this all the time.  It's what is in many walls, and if I started writing and rewriting all the problems with pink insulation, house wrap, and general bad building practices, I would be writing into the wee hours of the night.

In short, don't use pink insulation, don't use house warp, (good old shingle laid tar paper still is the best and cheaper,) and make sure you have a cold roof tied into a breathing wall system to create a air current around the thermal envelope of your structure.

Regards,

jay

[shinnlinger]

I wonder if I put a piece  of strapping in the middle of each bay vertically to create an airspace under the pink and drill a small hole at intervals right next to the strapping  so the wall can breathe a bit would be a good idea?  Zip wall is supposed to breathe!  But to be fair how can a piece  of painted OSB breathe?

Dave

[Rooster]

Is there a air space between the back of the board and batten siding and the osb sheathing?

[Jay C. White Cloud]

Zip wall is supposed to breathe!  But to be fair how can a piece  of painted OSB breathe?

So is Tyvek my friend, and in the lab it appears to most of the time, but not in the real world.  If I was called in on a job like yours, I would recommend a "cold roof," tied into a "breathing wall,"  and spray foam the wall to the point of your desired R factor, that way the "dew point" lands inside a waterproof insulative layer.

Regards,

jay

[shinnlinger]

Hi,

Rooster,

The B&B is applied right to the zip wall but the 1x10s are cupped slightly so I bet they breathe pretty good.

Jay,

If I put two layers of 2 inch foam (4 inches polyiso) on the inside of the studs, do you think I put the dew point in the foam?  I have a cold roof but drilling up my eve plates into it might create more problems than I have now but I have 5 ft knee walls so that certainly is a possibility.  Do you think a 1 inch hole for each stud bay up into the roof would work?  I could set a stop collar on an auger bit and probably pull that off with out much fuss actually.  My roof is zip roof topped with 3 two inch panels of polyiso with  a 2 and a 1/4 inch gap (2x + strapping) between the top of my foam and the steel roof

To make the best of a bad situation, I am thinking of putting attic vent panels on the walls to create an air space wherever I can.
http://www.google.com/url?sa=i&rct=j&q=soffit++baffle&source=images&cd=&cad=rja&docid=_t5u4wlBS0HTPM&tbnid=ok-pw8pRVYyVUM:&ved=&url=http%3A%2F%2Fhome.comcast.net%2F~atticpros%2Fventilation.html&ei=YrQuUcrKJqOX0QHn74HACg&bvm=bv.42965579,d.dmQ&psig=AFQjCNEO7WHKViJoE8HGrCYF5rqlQjsxew&ust=1362101731211725

[Rooster]

So just that I'm clear...this is a interior humidity/moisture/condensation problem, not a 'trapping moisture behing the siding" problem...correct?

[Jay C. White Cloud]

Hi Dave,

I feel worse than before for you.  I just don't know what to tell you that is optimistic.  I won't build without a breathing wall and cold roof interface, forming good convective flows around the thermal envelope.  When I saw that product hit the market I had concerns imminently.  If I was seeing this problem with regular OSB, what was this stuff going to do.  I really don't want to say this, but If was working for a client with this problem, I would be talking to the manufacture about some form of a settlement and/or fix on their dime, not my clients.  If you go with all foam insulation, I think you will be fine.  I would install a breathing wall as time and money allows.  I don't think you have a true cold roof form your description, I could be wrong.  A cold roof vents over the thermal envelope and out the ridge and gable.  Most of them have from 2" to 4"  (2"x4" on edge or flat,)  of space sleeper rafters on top of the insulation with no obstructions to the ridge.  It's about the same for the walls.  Keep us up to speed on everything, and good luck.

Regards,

jay

[shinnlinger]

Well I have a call in to HUber, but I do have a cold roof like you describe, the channels  runs from eve to peak, and I really think I can tap it pretty easily.  How big should I make the holes?

I kick myself on the zip wall as I knew deep down that painting OSB green doesn't suddenly make it permeable but they swore it allows 2-3 perms.  Whatever that is....

[shinnlinger]

and Rooster, you are correct, my problem is on the inside....

[Aikenback]

make sure you have a suitably sealed vapour barrier on the inside (warm, moist side), and everything will be fine. look for any signs of mold on the inside face of the osb and maybe spray it with a mild bleach solution or some  mold killing product where its necessary. it will dry out and stay dry with a proper vapour barrier.

[shinnlinger]

Aikenback,

I think you re right (what other choice do I have?) but if it only takes me a day to drill holes and $150 to buy and shove attic vent between the pink and the sheething I figure I should give it a go.

It will be interesting to hear what HUber has to say....

Jay,

You have any pics or diagrams of how you connect your breathing walls with your cold roofs?  It might give me some ideas.

thanks.

Dave

[Jay C. White Cloud]

Aikenback,

I'm sorry, I have to really challenge you on the concept of internal vapor barriers, all the research and field testing has shown they just don't work.  Moisture still gets behind them.  The worse cases of mold and pest issues I have seen are in structures, (commercial and residential,) with interior vapor barriers.  If you are using them and they are working that is great, but the only way to really tell, is tear out sample wall after five to ten years and look.  Most contractors that I know that still use them, don't do that, so there really isn't a way for them to know if they don't have mold and moisture in the thermal envelope.

Regards,

jay

[Jay C. White Cloud]

Dave,

I don't currently but I doing a project right now and I will make sure to take pictures for you.  Also, they can work in concert with each other or be independent.  What is important, is the chimney effect, bottom to top with a good draft.

Regards,

jay

[shinnlinger]

Is your current project in Vermont?  Would it be better if I saw it in person?

Dave

[Jay C. White Cloud]

Absolutely, it would be best in about two weeks, if all goes well on other jobs, but if you want to come by sooner I would love to help and talk through things with you if you would like.  Just let me know.

[beenthere]

I built my home in '67-68 with good poly vapor barrier on the warm side, then fiberglass insulation, southern pine plywood sheathing (sure didn't want to get that wet), and cedar board/batten siding. After 30+ years while adding a great room, these walls were opened up and there was no sign of moisture on the sheathing.

There are some good arguments that the vapor barrier inside isn't the best in the south where the reverse happens with cold air in the home from AC cooling causing condensation on the inside cold walls.

I agree that the mold on the osb is not a good thing, and looks to be a tough one to correct. Likely wasn't good to have the insulation in place and not a good vapor barrier on the warm side of that. But that is in the past. Need to look forward at this point.

[tyb525]

All I can add is, I've seen more rot, mold,and termite problems in homes built in the last 50 years, than the homes that are 75+ years old. One of the major differences seems to be plastic vapor barriers and house wrap.

[Jay C. White Cloud]

As you could tell I began to fall silent.  When folks find an opposite conclusion to what seems to be facts about a technique or method, I take a moment to ponder, but I must concur on those occasions that it is observed other wise, I too have seen more rot, mold, and pest damage in modern homes than I have in vintage.  Oddly enough the older the architecture, the sounder of condition in many cases.  I guess that is why I still tend to build as traditionally as I possibly.  I find that most modern marvels aren't as marvels when really looked at closely.  Just an observation. 

[jueston]

as i have said in other posts, for a while i dealt with situations like these full time, i worked almost exclusivly on stucco homes and homes with eifs, and it was my experiance that the problem was always breathing on the outside not the vapor barrier on the inside. that being said i think there i a big difference between MN and down south where there is more AC and not as much heat. but overall the idea is relativly simple, trapped water causes destruction. it has to escape in or out, and the design should plan for one or both.

as bad as what your looking at seems, i have seen far worse, i have worked on a few mansions where entire sides of the house were destroyed, every single stud so far gone that it had to be replaced or sistered with another stud, top and bottom plates with huge holes in them, headers that were nothing but dust. sometimes i would just look at the house with my engineering mind and be boggled how it is still standing. so looking at your pic my thought was that its good the framing still looks really good, which is a great sign, cutting out rotten and moldy framing and replacing it, is dirty horrible work, as i'm sure you know after pulling out that moldy pink insulation.

but it sounds like you have some good ideas rolling around in this thread and a good plan being formed, you just got to give the moisture someplace to go.

good luck.

[Jim_Rogers]

The only problem I see with drilling a hole to let the moist vapor up into the roof would be that it could also let a fire spread up there too....

I don't know if that would ever happen, or not.

Jim Rogers

[shinnlinger]

Its a valid point Jim, but I'm in a tough place on this.   Do I not vent because of the chance of fire and pretty much guarantee my walls rotting/mold issues , or do I take a chance and vent? Once flame gets in my walls, holes or not, Im afraid Im going to loose the house due to my rural location and volunteer FD so I think I need to take the chance. 

I am still wondering how big I should make the holes....

[shinnlinger]

Jueston,

How would you mitigate this problem?  What solutions did you come up with?

Dave

[jueston]

Well with stucco/eifs the problem is a little more straight forward, the point of water penetration into the wall is usually pretty easy to find. And once we found it, we repaired all the damaged studs and sheathing and another company came through and reapplied the stucco or eifs. The truth is, we really dealt with a symptom and never dealt with the disease, which was breathability. But we always used tar paper on the outside and not tyvek and the stucco or eifs being put on had some kind of drain system built in. but I wouldn't be surprised if in 10 years some of those houses will have problems again, I wasn't the GC while doing this, I worked for a GC who took his orders from the insurance company.

Your situation is less clear to me, I don't really understand if the problem is water coming in from the outside or condensing from the inside or both?

If its condensation, then it seems to me that foam will solve the problem, it will act as a moisture barrier and it won't trap the moisture like the fiberglass does. Since the condensation will be greatly diminished the small amount of moisture in the walls might be able to escape with the current level of breathability. Which would mean no need for drilling holes. But I can't give you any guarantees, just my opinion...

If I were to drill holes, I would go with many half inch holes instead of a few big holes, the reason is that I work on older houses and they tend to have a slight gap between the 1X's on the outside of the studs, a series of small holes would simulate these gaps between each board. Maybe 2 big holes would be just as good, I don't know.

[frwinks]

Encountered the same thing with my father's house a couple of years ago.  Typical warm interior air meets cold sheathing scenario.  His house was built in the 60-70's, pink insulation, poorly detailed VB, chipboard sheathing, vinyl siding.  Decades of freeze-thaw cycles and the house is still standing, with sheathing in tact.  It dries out every spring/summer to both exterior and interior..a breathing wall ;D  sorta'
The best approach would be to insulate from the exterior (keep the sheathing warm enough to push the dew point out of it, for your area 2" of Polyiso will do it).  If that's not feasible, you could do what I did on his house.  Preferred cavity insulation (paper, wool, rock, anything except glass) followed by a 2" layer of foilfaced polyiso.  At .03perm/inch polyiso is a very effective WRB/VB on it's own, the foil is an added bonus.  Devil is in the details, tubes of acoustical sealant, gaskets, spray foam, etc...you really have to go OCD on that stuff ;D  People will laugh and point fingers, but the way I look at it, at the end of the day they're not paying the bills for heating and cooling or wall replacements.  The ones who have no clue about building science will laugh the hardest while they drink free coffee at the pro desk
Top and bottom of the walls are critical to get air tight as well as all the post/beam connections.  Sheathing will still be cold, but at least you're preventing gobs of the warm interior air from hitting it and condensing on it.  Any condensation that does form on it will still be able to dry to the outside.
Is the siding attached directly to the zipwall? No rainscreen/strapping at all?     

For the roof, do you mean soffit vents?  Sounds like our roofs are similar in construction.  I have more insulation and two layers of 2x4 strapping with a 3" air gap washing down the insulation envelope.  Continuous soffit venting is the only way to go IMO.  Size depends on the roof area, but it's always better to oversize the air intakes.  Mine is a 4" wide strip, venting roughly 2500sqft of roof.  Do you have a continuous ridge vent?  You will need one.