Replies

1. Expert Member
   Michael Maines | Dec 30, 2009 01:35pm | #1

   Don, I don't know of a product that meets your need, but have an alternate solution. Would it be possible to use a rainscreen detail, spacing your stucco panels off the wall with vertical furring strips, with an air inlet at the bottom and an outlet at the top? That should eliminate the need for a permeable panel, and the wall will perform better in many other ways too.

2. 
   Don | Dec 30, 2009 04:12pm | #2

   Thanks M.M. for your reply.... The rainscreen detail adds time and cost...Besides, I have always been concerned that during really cold weather the circulation between the sheathing and finish would be poor...What prevents insects from occupying the space between? They seem to be able to get into any space if construction is not tight or if they chew their way in. Are these rainscreens perhaps a problem yet to come?
   Thanks again and happy new year..

3. 
   Riversong | Dec 30, 2009 11:25pm | #3

   Properly built rainscreens have insect screening bottom and top, but that is no guarantee of a permanent barrier.

   Another, completely overlooked problem with rainscreens is that they dramatically increase the fire hazard of a building, creating myriad little chimneys between cladding and sheathing. If a rainscreen is vented into the soffit, then the fire channels extend into the roof.

   Why not use some kind of exterior fiberboard sheathing or exterior gypsum sheathing?

4. Expert Member
   Michael Maines | Dec 31, 2009 11:40am | #4

   Don, Coravent has a product that includes window screening, or you can make your own.

   Robert, that's an interesting point about the potential for a rainscreen to become a conduit for fire. I would think that the shallow cavity would not be as dangerous as a full stud bay but still an issue. Providing an outlet at the top that does not couple to the roof vent (if there is a roof vent) is probably a good idea for that and other reasons.

5. 
   Don | Dec 31, 2009 12:06pm | #5

   Michael and Robert....thank you both for your interest and suggestions... I have had reservations about rain screen cavities, but Robert's remark about all those spaces being small dimension flues adds one more. Medium density fiberboards are loaded with urea formaldehyde and are large emitters. Also they creep... VIROC with its greater ratio of cement to wood fiber is very stable...Manufacturer claims that 1/16" space is sufficient between butt panels. I'm waiting for samples and literature...
   Meanwhile,, happy new year!

6. 
   Julia | Dec 31, 2009 08:05pm | #6

   Hi Don,

   I'm not a builder, so forgive me if I've misunderstood your question. But, I just learned about this stuff called Dragonboard that can be used on interiors instead of sheetrock, and on exteriors, too--it breathes! And, is insect-free. Made from magnesium oxide cement. Apparently, it's big in Florida where mold is a big issue. http://www.dragonboard.com/ Tomorrow I'll visit a site, here in Western Massachusetts, where a builder is constructing a healthy home. If the company website isn't all hype, this stuff is the best building material since the invention of sliced bread. Insect-free, mold-free, on interiors it goes well with American clay. So, if you can apply an exterior product that also will breathe, you might just have that look you're after. Happy new year!

7. 
   user-757117 | Jan 01, 2010 12:29pm | #7

   I found a product called Stedi-R by Georgia Pacific which claims to be a permeable and insulating structural sheathing panel. For a half inch sheet they claim R-1.32 and a perm rating of >15 perms. Sounds great but I wonder if anyone has verified these performance claims?
   http://www.gp.com/BUILD/productgroup.aspx?pid=1070

8. 
   Don | Jan 01, 2010 03:41pm | #8

   Thanks for the interest and suggestions.... Lucas, Stedi-R is a sheathing product...It needs to be protected by an exterior finish product which is what I have been looking for...and Julia, I haven't seen on Dragonboard's website information about permeability... The name and logo concern me a little..is this a Chinese made product??? I'm waiting for a response from them...

9. 
   Julia | Jan 02, 2010 12:42pm | #9

   Hey Don,

   No, it's not a Chinese product, but, there's another one floating around out there, apparently, that IS Chinese--they're not to be confused. Yesterday i actually saw the product on site. It can be used as exterior sheathing, though he's going to use it internally and apply Am. Clay on top. I believe the company says that it's cheaper than sheetrock, and this builder said, no way, not so. He also performed a stress test on it, by applying weight to one sheet, and it broke. "Sheetrock would never do this," he said. Again, not Chinese, but there is another brand of board floating around that is from China, and, if I'm not mistaken, it had to be removed from homes...? I'll be curious to hear what you discover. I'm waiting to hear from other builders who use it. (The company can say anything thye want...I want proof from the field!) Holiday weekend, no replys. But a guy in Brooklyn, NY, a furniture maker, was swearing up and down about its virtues, including permeability. Bau Biologie folks recommended it to the particular I met with yesterday. Ill let you know when I hear more. Best to you.

10. 
    Don | Jan 02, 2010 07:37pm | #10

    Julia...thanks for your input..... Is it your understanding that this stuff is meant to be used as sheathing rather than as a finish surface (which could be painted}?

11. 
    TmnqTLCWW3 | Jan 04, 2010 12:38am | #11

    Hey Don,

    I'm not sure. I'm sorry. I just sent an email to the contractor who's working with it. I'll get back to you.

    ; )