[Greenbuilding] Exterior insulation retrofit

John Straube jfstraube at gmail.com
Mon May 23 10:50:06 PDT 2011


That cavity is 20 mm wide!  That is an insane width for installation behind the EPS in an EIFS wall.
Products are considered to have a big cavity when they are 3 mm wide.  most are in the 1 mm wide.  
A 20 mm cavity will let a lot of air to flow through it, especially if vented at the top and bottom and then I would reduce the R-value by MORE than 50%.
But for the Sto, Dryvit, Synergy etc products on the market, the gap is just for drainage, not for ventilation.

On 2011-05-23, at 1:10 PM, JOHN SALMEN wrote:

> Hi John
> The original reference was from a current NZ eifs manuf spec. Sheet (BRANZ
> appraised) which required a .45 factor for derating anything outboard of the
> sheathing. The standard was NZS 4214 which is pretty old - here is an info
> sheet from BRANZ 
> http://www.branz.co.nz/cms_show_download.php?id=6d94af4d279466880e748b2d382c
> 7998e6fde45b
> 
> I don't know how the current standard has changed as I couldn't access any
> free versions of it but assume the drating is still in effect.
> 
> As for the liquid membrane we will be  using it. I'm pretty curious and the
> ext walls are all engineered shear walls so movement has been limited. To be
> honest the product application specifications I think put it in the grey
> area of overall credibility. Legally I think the liability is so diffused
> that the product cost is probably more related to managing risk than
> reality.
> 
> 
> 
> 
> -----Original Message-----
> From: greenbuilding-bounces at lists.bioenergylists.org
> [mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of
> jfstraube
> Sent: May-23-11 8:22 AM
> To: Green Building
> Subject: Re: [Greenbuilding] Exterior insulation retrofit
> 
> Hiya John
> Liquid applied membranes, at least the ones out there, are all significantly
> superior to mechanically attached sheet membranes.
> They can be applied to plywood or non-paper-faced gypsum (the paper facing
> was of course the biggest problem, not the gypsum).
> They all require joints to be treated with a tape of special mastic before
> roller/spray applying the membrane.
> I attach two photos of non-EIFS systems, but all the EIFS folks have their
> own as well.
> Even Tyvek now has a fluid applied air and warter barrier as part of its
> family.
> CCMC has tested these systems and included the testing of movements and
> drainage. I have tested several for drainage, and water resistance.
> In every way, except cost (they are more) and weather-sensitivity during
> construction (they need to cure before it rains), these fluid membranes are
> superior in performance, often significantly.
> 
> I know of a lot of work done at BRANZ, and have collaborated with them on
> their ventilated wall research, but I have not seen them tackle the heat
> loss question yet.  Any idea where this 20% (which seems very high) comes
> from? Could not find it by googling.
> 
> 
> 
> 
> 
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Dr John Straube, P.Eng.
Associate Professor
University of Waterloo
Dept of Civil Eng. & School of Architecture
www.buildingscience.com




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