[GSBN] Question about SB insulation at foundation

Wed Jan 25 17:38:36 UTC 2012

Hello all,

As our experiment/s with in-floor SB in Ship Harbour were cited by Bruce it  follows that I should comment on where
those are at today.

Background: owner/built 2 storey load- bearing SB constructed in 1993. 25' x 30' interior. Home has
been in continuous use since it was built  with virtually no repairs. Two skylights were added and a new roof
is due - likely this year (looking at metal or reed options).

Infloor SB: the house sits on old telephone poles set 4' below grade/frost line. The back of the house is about 2' above grade
and the front is about 5' above grade. Several layers of newspaper are laid out between two - three layers of spruce board flooring.
Before the floor was laid 2-string  bales were ripped in half between the strings with a chainsaw. The resulting 9"x 14' x 34" bale lengths
were flipped "flat" onto a stretcher and carried to the floor and friction fit between the floor joists.  All well and good to here. 

The problems I had resulted in trying to account for (possible) rising damp by attaching a sheet of 6 ml. poly to 
the underside of the floor assembly .... and then by not adequately flashing  where the poly hit the perimeter joist - creating a perfect opportunity
for wind-driven rain to collect on the poly on the underside of the bales. 

Once the problem was recognized (water collecting on the poly) it was mitigated by slashing the plastic and flashing the edges. 
I will make a point of doing better forensics this summer to look again at what is going on under there. All that being said I think
there are good opportunities for using bales in floors that are above grade, if there is sufficient ventilation or other strategies to account for rising damp. 
There is much to be said for building on piers/post.... and it is (I think) an under-utilized, lo-impact approach to current floor options. 

The other insulation material we are very excited about here is wool. Currently 75% of the fleeces here in NS end up in the land fill!
 Such a waste. So many possibilities for small scale localized treatments.

All the best,

kim

On 2012-01-24, at 12:32 PM, Bruce King wrote:

> 
> The idea of using any cellulosic material at or near grade just makes me nervous and ill.  We have a world of experience telling us that wood, paper-faced gypsum board and straw don't last long there, or anywhere near there.  Recall Kim Thompson's well-documented problems using bales between floor joists over a Nova Scotia crawlspace.
> 
> But how, then, to insulate?  I guess I would argue for the use of a naturally-occuring substance that can make a durable and also effective insulator in the presence of moisture, namely petroleum.  It takes a bit of unpleasant processing to turn oil into foam (that is, something that entraps air which is the real insulator), and god knows we need to improve on the weird stuff currently on the market.  But if there is any good use for petroleum, this is surely one.  Not for our cars, not for crappy plastic packaging & throwaway junk, but for effective, durable, reuseable insulation.
> 
> Or anyway I'm still waiting for a viable "natural" ground insulation suggestion that isn't a super labor intensive fuss job.
> 
> Shredded plastic bags, anyone?
> 
> Thanks,
> 
> Bruce "Oil gladly pay you Tuesday for some polyisocyanurate today!" King
> 
> 
> 
> On Jan 24, 2012, at 8:08 AM, Frank Tettemer wrote:
> 
>> Hi all,
>> 
>> I have just received a message from the designer of the yoga centre, that I was busy criticizing in my previous post.
>> The Sivananda Yoga Centre is still alive and well over a decade later.
>> 
>> I apologize to the GSBN group, and to Michel Bergeron, for handing down that mis-information about the Sivananda Yoga Centre. Michel has had no such reports of mold problems, and as the designer, he would certainly be the first to hear about it.  It takes a foolish commnet from someone like me, to deeply upset the credibility of straw bale construction. And worst of all, this negative comment coming from a straw bale builder!
>> 
>> There's a strong lesson in all this for me, to examine all my sources of information, and to not speak about things of which I have no first hand knowledge.
>> 
>> Deeply chagrined, deeply humbled,
>> 
>> Frank Tettemer
>> 
>> 
>> On Jan 24, 2012, Derek Roff wrote:
>> I'm not sure if this discussion is still alive on the linked site that Joyce posted.  The newest posting is just about a year old, but perhaps the discussion will warm up again.  Bruce King posted a comment last year, when the discussion was current.
>> 
>> Something that wasn't mentioned in the article or comments is the naive assumptions regarding the effective insulation value of the strawbale waffle slab design, even before the bales start to rot.  The assertion is made, and not challenged, that the under-slab strawbale insulation would provide R-50.  Whatever number we accept as the insulative value of each bale, the thermal bridging of the concrete in the matrix would cut the effective insulation of the waffle slab design dramatically.  Thermal bridging isn't a problem with the design sketch that Joyce included, but the risk of rot probably remains.
>> 
>> There is an alternative approach that uses bales as floor insulation, but above grade.  After a European Straw Building gathering a few years ago, traveling with Catherine Wanek, I visited SB buildings in half a dozen countries, including several that used strawbales in the floors, to meet Passiv Haus design goals.  All of these structures were build on piers, so that the bales were above grade and isolated from the moisture concerns that afflict buried bales.  Here is a link to one example, the S-Haus in Austria.
>> 
>> http://www.s-house.at/presentations.htm
>> 
>> Bale-on,
>> Derelict
>> 
>> Derek Roff
>> derek at unm.edu <mailto:derek at unm.edu>
>> 
>> On Jan 23, 2012, at 10:40 AM, Frank Tettemer wrote:
>> 
>> Well now,
>> that is pretty interesting.
>> Thanks, Joyce, for sounding the alarm.
>> 
>> Before I actually (physically and personally), had built any SB houses, I naturally ass-u-me-d that bales in the floor and ceiling were a good idea.
>> It is too bad that the article in finehomebuilding references the experimental work of Michel Bergeron, of ArchiBio, in the ground-breaking book of Steen/Steen/Bainbridge/and Eisenberg.  I love the book, and it is what gave me hope for the idea of burying bales below grade.
>> 
>> Fortunately for me, Linda Chapman, (archi. from Ottawa), talked with me about doing this in the early nineties.
>> She had boldly gone where no one had gone before. And the floor rotted.
>> 
>> And there was the evidence from the huge three-story yoga retreat centre, built in Quebec,
>> which was such a rotten embarrassment, that I won't mention it anymore.
>> 
>> Then there's the theory that if you stick each bale into a garbage bad before you bury them under the floor ...
>> just to say I did, I took a bale, put it into a garbage bag, and placed it into a weather-protected shed, to see what happened.
>> First of all, it took three trys with the garbage bad to place a bale into it, without it being punctured by straw.
>> Secondly, during the summer of 2000, which was a fairly wet year, the bale self-composted, with out having had a drop of rain on it. I imagine that relative humidity was all it took. It was full of mildew in two months time.
>> 
>> I have to say, though, that the idea is so intriguing, that it captures the imagination of quite a few clients, who would wish me to design a foundation using straw bales.
>> Maybe it's just a stupid idea, here in a climate with huge weather extremes, (+35C to -35C), and many days of damp rainy weather?
>> Maybe all the ideas have not been tried as yet?
>> 
>> Frank
>> 
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