[GSBN] Earth plaster and Cellulose and Congratulations!!

Tue Apr 30 11:18:36 UTC 2013

First .... to all who have worked so hard on SB code issues over the years - thank you for your dedication and passion.
There is a resounding ring of hope circling the globe as Martin's latest news spreads and congratulations roll in. So inspiring.
-------------------------------------------------------
Hi Jacob,

Thank you for your thoughtful comments on my question about insulation/air barrier options for the Morris.
I will share them with committee members and let you know what transpires.

Regarding access to the wall cavities -  removal of damaged plaster and inserting holes
as needed to pack cellulose (or other insulation) have been discussed. Your mention of
drying time for straw clay are well taken - this is certainly an issue in our climate. We have had an
air source heat pump donated to the project  which could, we conjecture, (this is new technology to me)
 contribute to accelerated drying of whatever materials we use.

Am continuing to work on the wool insulation option - the local agricultural college is doing experiments in this area and
we hope to use some of their products this year. They are using success of wool batt and blown in, in UK and NZ for their marketing plans.

All the best,

kim

BTW I do indeed know Annie M, Nova Scotia is small!  Just had a view of her starring role in S*** 

Also you may be interested in having a look at a report I did a few years ago for CMHC looking at best practices and challenges for 
building with straw bales in Atlantic Canada. While wood cladding and/or other rain screens are being used on many projects, I wouldn't say
they are the norm. Adding this extra skin is generally recommended on a case by case basis - it is especially effective where a building is exposed to 
our driving horizontal rains, however for material conservation and aesthetic it is often not specified.  Verandas and generous overhangs are often used as well.

Report can be ordered for free from Tel. 1 800 668-2642. Be sure to ask for the full report 
which includes a 20 min dvd of interviews with bale builders and a data base of the of 40+ buildings profiled.
Straw Bale Construction in Atlantic Canada
HIghlights and Full Report   #65828
Order desk: https://www03.cmhc-schl.gc.ca/b2c/b2c/init.do?language=en    

On 2013-04-28, at 11:55 PM, Jacob Deva Racusin wrote:

> Kim,
> 
> Wow, what a great project!  That's a really dramatic image of the Morris House next to the massive glass-faced skyscraper...good on ya!
> 
> I'm a bit hesitant to reply given the tremendous wealth of knowledge on this list, but it's a great question so I'll take a crack.  My understanding of 'nogging' is brick non-structural cavity infill, yes? And you are looking to insulate the empty cavity sections above the brick?
> 
> The concern about creating a moisture problem by introducing insulation is a valid one - there is plenty of precedence for this unfortunate dynamic.  The introduction of insulation reduces the drying potential of the assembly, and can create condensation problems which did not previously exist.  Insulation can be introduced safely, however, if moisture sources are considered and mitigation strategies are designed into the work.  First and foremost, keeping bulk liquid moisture out of the assembly is critical (wind-driven rain and window leaks are two notorious and insidious examples).  That's the most significant source of moisture damage, and even a small window leak that might have previously gone undetected can become a bigger problem when heat loss from inside the building is shut off and drying potential is reduced.  The next step involves air-sealing, which you reference would be part of the protocol.  This is critical to reduce bulk-loading of moisture vapor into the wall through air leakage.  When I do building performance work, I see plenty of examples of weatherization work done in the 80s, when insulation was added in attics without air sealing, and it is not uncommon to see evidence of moisture damage in particularly leaking locations.  I'm unclear as to how you would be accessing the interior of the cavity and addressing air leakage, but this would be an important move prior to/in concert with insulating (I note that none of the insulation materials you reference are air barriers themselves, requiring a separate air sealing approach).  In your climate, air-sealing from the interior - stopping the moisture drive at its source - is desirable, although a primary air barrier on the exterior can work well too if the detailing is tight and the air barrier is vapor permeable enough to allow drying to the exterior as need be.  You mention that there is no vapor barrier in the wall assembly; myself, I prefer such vapor-open strategies, but it is very important that these be deployed with rock-solid water control and air-tightness measures to be effective.  Diffusion through materials alone is very unlikely to cause a problem, but can push conditions in a wall or ceiling into a danger zone if there are other moisture issues also at play. 
> 
> I like dense-pack cellulose because it has a relatively high R-value compared to other in-fill insulation, is fire-retardant without the use of HFRCs, performs a notable amount of air circulation retardation (not an air barrier, but does slow movement down a good bit), has a high hydroscopicity that allows concentrations of moisture to disperse throughout the material (avoiding higher concentrations in specific areas) and dry out if given the opportunity, is pretty ecologically-benign and not too industrially-intensive (depending on the specific product), and installs dry - a big plus compared to many of the wet-wall natural building materials I otherwise favor using.  I am unfamiliar with aerogel in practice, only in theory, so I won't comment, but my bigger concern around straw-clay and hempcrete would be the amount of built-in moisture you are introducing into the cavity.  Provided you can ensure adequate drying within a reasonable amount of time they could work fine if you are alright using a relatively lower-R material, but since moisture is a chief concern of your committee that might be a harder sell.  We don't have much access to affordable wool insulation, but that could be an attractive option - again, providing thorough air sealing measures are taken, as it will be unlikely to stop air flow to any appreciable degree.  I like the idea of the reused brick - the lowest insulative value of any on your list, but I like the nod to finishing the original design, for whatever that's worth (perhaps not much, if your goal is to maximize comfort for the inhabitants).
> 
> I hope that helps.  There are some great case studies on both GreenBuildingAdvisor.com and BuildingScience.com that provide some good examples of similar situations, I can dig up some examples off-list if you have trouble finding them.  Best of luck, keep up the good work!
> 
> Jacob
> Jacob Deva Racusin
> New Frameworks Natural Building, LLC
> P.O. Box 15, Montgomery, VT 05470
> (802) 782-7783 (c)
> (802) 326-2209 (h)
> www.newframeworks.com
> jacob at newframeworks.com
> On 4/26/2013 12:50 AM, kim thompson wrote:
>> Hello all,
>> 
>> I have had a note in progress for GSBN'ers for weeks to ask a question related to Jacob's.
>> A building I am currently involved with was built in 1764. We recently moved the 2.5 storey home 
>> nearly 5 km through central Halifax to a lot where it will be rehabilitated and used for affordable housing for youth.
>> 
>> The Morris House has become an interesting demo of how we can make heritage buildings more energy efficient (and
>> keep them out of the land fill). It has a number of unusual (for Halifax) features including solid brick nogging which fills the cavities in the
>> first and half way up the second floor levels of the Georgian timber frame. There has been considerable discussion amoung committee members
>> involved with the Project about whether or not to fill in the currently uninsulated wall sections, and if so with what. Heritage folks want to employ 
>> minimal intervention strategies and add nothing - they are concerned that introducing insulation will bring with it moisture which will 
>> compromise the timber frame.
>> 
>> I have proposed a few options and would so appreciate thoughts from this group on the building science side of things for
>> our northern maritime climate. Thermal comfort (cold walls especially) will be important to the young people living there, as will be 
>> heating costs... construction materials and systems on this project will certainly be cited as recommendations for future heritage rehabs. 
>> 
>> So my question is  what might be the pros and cons of insulating the currently empty wall cavities above the nogging with one of the following:
>> (a) dense pack cellulose (b) light straw clay (c) hempcrete  (d) reuse of brick from the chimneys of the Morris. (e) blown in or batt wool  (f) aerogel.
>> Assuming any one of these would be installed with great care to avoid air leakage. 
>> Exterior cladding is painted cedar shake, interior is lime plaster/lathe, no vapourbarriers and removal of  the nogging is not an option.
>> Are there other choices apart from providing "extra sweaters"  for the tenants that would not compromise of the structure.
>> 
>> Am hoping that John S. in particular might chime in on this.
>> 
>> Thank you all!
>> 
>> Kim Thompson
>> www.themorrisproject.ca
>> 
>> 
>> On 2013-04-25, at 11:46 PM, Jacob Deva Racusin wrote:
>> 
>>> Hello,
>>> 
>>> My apologies for the cross-post, but I'm trying to do a very quick and broad survey.
>>> 
>>> I was just contacted by a former student I am advising, who is project managing a building currently in design phase, in the mid-Atlantic region in the eastern US.  The wall assembly was initially to be straw-clay, with plaster finish on both sides. Budget and logistics have directed an insulation switch to cellulose.  He is currently advocating for wood lath with lime-stabilized earthen base coat, with finish lime coat (our standard approach for finish exterior plaster).  The architect is balking, suggesting that the moisture storage and release dynamics for which we rely upon the plaster in straw-based designs will not play out the same way with cellulose, that the cellulose will be overwhelmed with moisture and push the dew point deep into the wall.  This is all second-hand reporting of the conversation - I know no more than what I just reported - but I am due to speak with the architect and client tomorrow on my student's behalf, and I'm curious as to whether or not any of you have direct experience with earth base plaster over wood lath outboard of a dense-packed cellulose-insulate wall, or any reason to believe the cellulose would not behave adequately in concert with adjoining plaster (as opposed to straw).
>>> 
>>> The architect is spec'ing (outward from the framing) plywood, housewrap, drainage gap, stucco lathe, plaster.  My impression is that this suggestion would certainly work, but is hardly the natural wall system initially intended.  It seems to be playing off of the concerns of sun-powered vapor drive pushing vapor deep into the wall cavity as a result of a reservoir cladding adjoining the insulation.  As long as there is no interior vapor barrier or Class II vapor retarder, I feel this dynamic is identical to that we've created with straw-insulated walls, and if anything the cellulose would stand up better to incidental vapor or liquid moisture intrusion.  Also note generous overhangs and 24" grade separation are spec'd in the design, as is multiple coats of limewash (and potentially a silicate top coat for durability), which will further reduce bulk water absorption and minimize incidental solar-powered vapor drive.  The wall is designed to dry to both sides of the assembly, in keeping with the variable moisture drive of that region.
>>> 
>>> Perhaps there is another concern here I'm not understanding - I'll find out more tomorrow - but in the meantime if anyone has any perspective on why this situation would work for straw, and not cell, or any direct experience in a comparable climate executing such a system, I'd be grateful for your input.
>>> 
>>> Thanks so much,
>>> Jacob
>>> 
>>> -- 
>>> Jacob Deva Racusin
>>> New Frameworks Natural Building, LLC
>>> P.O. Box 15, Montgomery, VT 05470
>>> (802) 782-7783 (c)
>>> (802) 326-2209 (h)
>>> www.newframeworks.com
>>> jacob at newframeworks.com
>>> 
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>> 
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