[Greenbuilding] Exterior insulation retrofit

Mon May 23 10:21:39 CDT 2011

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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On 2011-05-20, at 9:03 PM, JOHN SALMEN wrote:

> I'm a bit stuck on this one. Not fastening mechanically means relying on a
> liquid applied wrb typically on a gypsum board - which is the recommended
> substrate. Now as in the past that will work great for 95% of the surface
> but any seam larger than 1/4" will be a problem (as per 'high performance'
> barrier suppliers spec). I've rarely seen any kind of sheathing applied that
> does not have larger gaps somewhere and have also seen sheathing buckle as a
> result of no gaps. Also 2x framed buildings move, foundation settle, etc... 
> 
> In my thinking any sheathing with a liquid membrane will not be complete and
> will typically fail along an otherwise impermeable drainage path (isn't that
> how things work) largish cracks in an impermeable path allow large flows
> which prevents any potential for drying in that path (despite the gap) which
> results in some spot of saturated wood/gypsum that has limited drying
> potential and becomes food for decay.
> 
> Mechanical fastening perforates the wrb thru the drainplane with probably a
> couple of holes per sq.ft. which could also lead to problems but I can't
> help but think that most flows in this situation would be directed as
> drainage against a layered wrb and any moisture thru a screw hole has
> greater potential for drying in the assembly.
> 
> I am saying this as I am considering using a liquid wrb on a ply sheathed
> building and my common sense tells me that it is the wrong approach - I am
> embarrassed to say that my concern is the aesthetic telegraphing of the
> screws (which is all anyone sees) as well as being in compliance with some
> local practice.
> 
> By the way I think NZ has quantified the insulation loss for air movement
> with drainplane for eifs at something around 20% (if memory serves) as a
> code modification for insul. Values. I need to check that memory.
> 
> John
> 
> 
> -----Original Message-----
> From: greenbuilding-bounces at lists.bioenergylists.org
> [mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of John
> Straube
> Sent: May-18-11 7:24 AM
> To: Green Building
> Subject: Re: [Greenbuilding] Exterior insulation retrofit
> 
> The class action suits Eli mentions where in the early 90s were not drained,
> relied on caulking to keep water out.  Not surprisingly, caulking failed,
> windows leaked, and disaster ensued.  Drained systems have not had these
> problems.
> The question: "does a drained gap behind the insulation short-circuit
> insulation" has not been definitively answered. It has been studied and
> reported on however.
> What is clear is that a small gap (say 1/16" or less) with a drain opening
> at the bottom only works very well as a drainage system and has a small
> impact on R-value.  How small? Hard to tell, but under 10%, and my best
> estimate is 3-5%.
> If you have larger gaps and vent openings top and bottom, then the loss will
> be greater and can be rather significant in theory.
> So, use a small gap and vent only.
> Also, if you dont like EPS foam (Rob Tom?) you can install EIFS over high
> density Rockwool.  We tested such a system in the mid 90's, which had large
> vent openings (trying to get pressure equalization, which was the fad then),
> and could not see any impact on R-value, but it was a field test so we cold
> not really measure better than 10%.
> 
> The drainage plane on the substrate should be high quality: building paper
> does not cut.  EIFS producers sell fluid applied air and water barriers that
> are high performance.
> 
> The most problematic EIFS are those that use mechanical fasteners (screws)
> through housewraps.  While they can work, the screws tend to move and cause
> cracking far too often, and the differential moisture absorption around the
> screw causes slight discoloration.  After brief flirtatons with mechanically
> fastened EIFS, most suppliers have gone back to the tried and true
> adhesively attached version.  While many on this list would prefer not to
> rely on adhesion (I am one of them) there is a very long track record of
> success with EIFS, and there are enough problems with screw attachments to
> make me avoid them.
> 
> 
> 
> For stucco (cement, sand mixes) cladding over insulation, different rules
> apply.
> 
> 
> On 2011-05-18, at 9:58 AM, elitalking wrote:
> 
>> Exterior Finish Insulation System does provide the exterior finish,
> thereby reducing the cost of another finish. I know dryvit had a class
> action lawsuit that was settled for bulk water drainage problems.
> Ultimately the solution was to assume imperfections in the flashing
> installation and manage the water by overlaying a building wrap on original
> wall with a drainage space maintained.  My question is does that drainage
> space on the conditioned side of the insulation create a convective path for
> air leakage? In the best of all worlds, the building wrap would be a perfect
> air barrier. Just as with the bulk water flashing, perfection is hard to
> achieve.  Could that be a source of air leakage from the building?
>> 
>> In my installation, I located the bulk water drainage outside the
> insulation with 3/4" osb furring strips for siding screws.  I attempted to
> seal between the insulation boards to achieve tight air barrier.  I also
> added a redundant building wrap layer to do the same.  Both were vulnerable
> to imperfections.  However, there is no known hole on conditioned side.
>> 
>> Eli
>> ----- Original Message ----- From: "John Straube" <jfstraube at gmail.com>
>> To: "Green Building" <greenbuilding at lists.bioenergylists.org>
>> Sent: Tuesday, May 17, 2011 9:42 AM
>> Subject: Re: [Greenbuilding] Exterior insulation retrofit
>> 
>> 
>>> Being done all the time in North America.  Although this really only got
> common in the last decade.  I expect to see a lot more.
>>> The problem is, you have to like the look of stucco, which is not always
> what is wanted, and the impact resistance of EIFS leaves lots to be desired.
>>> 
>>> On 2011-05-17, at 9:27 AM, Norman Feldman wrote:
>>> 
>>>> In April I heard an architect describe how they're using EIFS insulation
> in Germany and Austria to insulate existing buildings from the exterior.
> They apply EIFS panels to the outside of the building while tenants are in
> the building then, once the insulation is done, bring the windows out. I
> will forward more about this offlist if anyone wants.
>>>> 
>>>> http://en.wikipedia.org/wiki/Exterior_Insulation_Finishing_System
>>>> 
>>>> 
>>> 
>>> Dr John Straube, P.Eng.
>>> Associate Professor
>>> University of Waterloo
>>> Dept of Civil Eng. & School of Architecture
>>> www.buildingscience.com
>>> 
>>> 
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>> 
>> 
>> 
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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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John Straube
www.BuildingScience.com