[Greenbuilding] wall envelope - rainscreen

Sat Oct 16 14:15:30 CDT 2010

SCRUNCH – I think that is the sound that an optimistically labelled  ‘high density’ roxul board makes when you step on it and your foot compresses it by a few inches.

Or it could be the expression your face makes when after ‘scrunching’ the board with your foot a nasty cloud of fibres and formaldehyde fill the air.

I had a stucco contractor substitute a similar drainage wrap (spun polyolefin). I wasn’t too keen on it as it was one of these horizontal rain hillside 3 story exposures. The material is so coarse that all I can imagine it doing is holding or directing water against both the sheathing and the stucco. Also you end up with a lot of fasteners all over the place (then doubled with the stucco mesh going over). It looked pretty scrunchy, especially when it had to be cut into small strips to fill in areas. Also it was pricey. 

Roxul makes a 1” drainboard that could be used and it at least offers some insulation value (but with air and water flow?). Same problem with holding water though and the only thing that is going to dry it is ventilation air. It is about 6lb density and probably would have to be run between furring. Not sure how that would comply with code for open area on 16” spacing (and then there is all that urea formaldehyde stiffening those fibers) 

Sorry for confusion about battens – they are not banned but the code requirement here (if someone is being a pain) is 1” nail penetration – so one inch strapping if you are putting it over foam. So for 3” of exterior foam you need to fasten 1” battens with a min. 5” fastener thru to the framing – and then secure cladding to that with full 1” depth fasteners. Basically gets unworkable.

Green guard has another drainmat product that is a dimpled xps sheet ¼” thick that is run over a wrb that is continuous channels rather than a spun mat

JOHN SALMEN ENVIRONMENTAL DESIGN

4465 UPHILL RD,. DUNCAN, B.C.  CANADA, V9L 6M7

PH 250 748 7672 FAX 250 748 7612 CELL 250 246 8541

terrain at shaw.ca

  _____  

From: greenbuilding-bounces at lists.bioenergylists.org [mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of Alan Abrams
Sent: October 15, 2010 12:55 PM
To: ArchiLogic at chaffyahoo.ca
Cc: greenbuilding at lists.bioenergylists.org
Subject: Re: [Greenbuilding] wall envelope - rainscreen

SCRUNCH  (skrʌntʃ)  V.T.  To deform an object, posture, or face, by some means of compression, distortion, bad taste or smell, etc.

the "ban" was the prohibition against hanging siding from furring strips over foam, in John Salmen territory.  

Speaking of John, who, as Lincoln would have it, is "the one who commenced this fuss" -- my project manager just walked in a few hours ago and handed me a brochure for "RainDrop Green Guard Building Wrap" by Pactiv.  

The product is "scrunched" in some fashion to provide drainage channels, "no matter how tightly cladding is nailed to the wall."  16 perms.  15 mils thick.

There you have it.

AA

Alan Abrams
Abrams Design Build LLC
A sustainable approach to beautiful space
 <mailto:alan at abramsdesignbuild.com> alan at abramsdesignbuild.com
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On Fri, Oct 15, 2010 at 9:55 AM, RT <ArchiLogic at yahoo.ca> wrote:

On Fri, 15 Oct 2010 08:52:40 -0400, Alan Abrams <alan at abramsdesignbuild.com> wrote:

would the roxul in this case be rigid
enough to scrunch down furring strips against its surface, and stay like
that for a while, to support horizontal siding?

this of course presumes the ban against furring over exoinsulation does not have a lot of merit.

Huh ? "Scrunch" ? Vass iss dis "scrunch" ? Don't know "scrunch". (Sounds like a sugary kiddies breakfast cereal)

And "ban against furring over outsulation" ? I didn't know there was a ban.

But taking a stab into the dark...

Would the word "Z-channels" be of any use here ?

(They are often used here in MooseLand with the semi-rigid mineral wool boards to provide attachments for siding.)

WRT the ban on furring strips:

What is the intent of the ban ? Does it have to do with concerns about creating leetle chimneys for fire that would schwoop up and make short work of foamed plast-eccchh! outsulation and then result in the whole exterior falling off in a spectacular flaming mess ?  (I just made that up but it sounds pretty good. Eh ?)

If so, the ban may not apply to Roxul since it doesn't burn and the use of Z-channels would make the point moot anyway since there would be no air gap.

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Kanata, Ontario, Canada
< A r c h i L o g i c  at  Y a h o o  dot  c a >
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