[GSBN] Question about SB insulation at foundation/ceiling

[David Arkin, AIA]

In slab on grade situations we're now using mineral wool, aka rock wool, which is available in panels and becoming increasingly easy to get here in the US, and it's been around for quite some time.  Roxul is one brand:  http://www.roxul.com/building+envelope/products/roxul+drainboard®

They claim that the energy used in manufacturing is recovered within three weeks of installation.  It isn't the least expensive solution, but it is entirely rot resistant, and it isn't petroleum.  We've also used EPS under slabs, employing the wisdom of Buckminster Fuller, "We have more than enough petroleum to meet our needs, if we'd only stop burning it."  Rigid foam insulation which enables a building to need less heating or cooling is a justifiable investment, imho.

That all said, this idea of bales under a floor - even a slab on grade - intrigues me, and I do believe one can create a condition where the risk of rot is minimized.  However, building occupants would need to know that frequent (or maybe any) mopping of floors is not possible, and I'd still prefer to see the bales considered as sacrificial.  If the bales were staggered slightly in both directions one could have occasional piers (roughly 2' (0.6m) o.c. in one direction and ±3'-9" (±1.15m) o.c. the other, depending on bale size) that would take over the supporting of the floor if the bales were to deteriorate.  

And of course John Straube beats me to the 'send' button yet again!

David 


On Jan 24, 2012, at 11:17 AM, forum at lamaisonenpaille.com wrote:

> It is true that (raised) SB floor insulation are getting more popular here in Europe but this worries me somewhat because in my pré-SB life I have seen at least 3 floors with water 'standing' on it due to : a frozen water pipe, a broken down washing machine and (the most fun) a friend who put a few beers in the botom of the shower and he opened the tab so the running water would cool the drinks while taking a siesta in our spanish hotel in my 20's. His nap was interupted when the people below saw water comming through the ceiling...  My moral of the story : If  don't use waterpipes in cold countries, wash in an outhouse and be carefull when choosing your friends if you use 'compostable' floor insulation. 
> Sure, some claim that they detail in such a way that water cannot penetrate, but I wonder how this is done in a perfect, cost effective and durable manner. In any case, the french insurance companies made sure SB floor insulation was deleted from our proposal for the recently approved french SB building rules (I wonder why? ;-).
> 
> An interesting technique sometimes used in France is using a tiny fan to blow the hot air (from below the roofing) through pipes under the slab (at a well calculate dept) so that with the time lag this heat comes up during winter. Seems like a clever idea to take away the heat where we don't want it in a way it becomes available where and when we do appreciate it. I have no details of it and there might be practical disadvantages that makes this system less ideal than one might think...
> 
> André - fan of locally made slippers - de Bouter
> France
> 
> 
> 
> 
> Le 24/01/2012 19:10, Laura Bartels a écrit :
>> 
>> In the project I just finished, we used bagged perlite insulation over 6 inches of 3/4" washed gravel covered by a vapor/radon barrier. The perlite was tamped, finishing at 7" for an R-value of 21.9. It is a regional material here, minimally processed, light to transport, and non-toxic. So far, I'm very satisfied with this choice and would like to do more with this material. It is installed under an adobe floor with good results. I had had conversations with Daniel Silvernail, who had also used perlite underfloor, as well as builders in the northwest US. I know there's been some discussion of perlite on this list which I believe I missed due to my schedule at the time.
>> 
>> On a related note, I have just spent a few days with Arlene Blum, PhD and director of the Green Science Policy Institute and learned much more detail of the toxicity of flame retardants which are added to most foam building insulations as well as foams in furniture. More info can be found here - http://greensciencepolicy.org/non-toxic-building-materials. There are some very interesting elements of this issue, one of which is that the flame retardants not only give little reduction in burn time (as in seconds) but also add several additional problems if a fire does occur, such as increased carbon monoxide, soot, along with the cancer causing chemicals that are unregulated as they do not fall under the jurisdiction of EPA or FDA, but are mandated through building standards. And for underslab insulations, flame retardants don't make sense anyway. 
>> 
>> Best,
>> Laura
>> 
>> 
>> Laura Bartels
>> GreenWeaver Inc.
>> 520 S. Third St., Suite 5 
>> Carbondale, CO 81623
>> 970-379-6779
>> www.greenweaverinc.com
>> 
>> 
>> <Mail Attachment.jpeg>
>> 
>> 
>> We've moved to the Third St. Center 
>> http://thirdstreetcenter.net/
>> A community place promoting inspiration, sustainability and creative exchange
>> 
>> On Jan 24, 2012, at 10:09 AM, Derek Roff wrote:
>> 
>>> It would be nice to be able to choose from a richer range of choices than the functional, but high embodied energy, toxic, petroleum foam vs. a more benign product that may rot.  Making a "lesser of two evils" choice guarantees choosing something evil.  It would be great to have ten choices with generally positive attributes, but we do have at least one additional option.  As I understand it, Roxul Drainboard rigid mineral fiber insulation is more environmentally benign than petroleum foam, and more resistant to destruction from human, insect, and rodent activities.  One of the comments in the links that Joyce gave indicates that Roxul Drainboard was selling at a lower cost per R-value, as well, at that time in early 2011, in Virginia, if I remember correctly.  I've never used it.  Any comments from someone who has?  Any other alternatives that you favor?
>>> 
>>> Derelict
>>> 
>>> Derek Roff
>>> derek at unm.edu
>>> 
>>> On Jan 24, 2012, at 9:32 AM, 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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