[GSBN] using loose straw insulation in roof

Martin Hammer mfhammer at pacbell.net
Wed Nov 1 07:58:23 CDT 2017

Thanks for the info John. I was grasping at the straws of my memory for the
story on the ³China² fire event (and almost said ³or Mongolia²). Not sure if
we¹re thinking of the same event. Either way the point is the same. In
addition to: Don¹t install a chimney against insulation (straw or any
other). Thus "Section AS107.3 Clearance to fireplaces and chimneys² in the
IRC strawbale appendix.

One side note. I sent that last email on Oct 27, but GSBN didn¹t receive it
until Oct 31. Anyone else ever experience a multi-day delay?

Martin (traveling at the speed of straw) Hammer

From:  Gsbn <gsbn-bounces at sustainablesources.com> on behalf of John
Swearingen <jswearingen at skillful-means.com>
Reply-To:  GSBN <GSBN at SustainableSources.com>
Date:  Tuesday, October 31, 2017 at 7:04 PM
To:  GSBN <GSBN at SustainableSources.com>
Subject:  Re: [GSBN] using loose straw insulation in roof

Thanks for all that, Martin.  One note, if we're talking about the same
incident with Kelly, it was a clinic in Mongolia that caught fire shortly
after it was built, because the had installed the fire chimney after the
attic and insulation, and right against it.  The fire brigade was quite a
distance away, many hours, and because the straw was just smoldering, they
had time to move all the equipment and furniture out from the building,
without damage, and then the fire in the attic was extinguished.

John "Insolent Insulator" Swearingen

On Tue, Oct 31, 2017 at 6:52 PM Martin Hammer <mfhammer at pacbell.net> wrote:
> Hi all,
> Good discussion and advice on this.
> The PAKSBAB (Pakistan) SB buildings use 12² (30 cm) of clay-coated straw for
> insulation above the ceiling (photos and drawing attached) (second photo and
> drawing courtesy of Darcey Donovan Messner). Andy Mueller and I used a lesser
> depth of the same ³loose straw-clay² for our SB building in Haiti (photos
> attached).
> Both make a noticeable difference in the building's thermal performance in
> their respective climates. In both cultures thermal insulation of any kind is
> rarely used. But as happy as I am to use this inexpensive natural insulation
> in these and similar contexts, I worry about the flammability of the ³loose
> straw clay². Even if the material resists ignition in the first months or year
> after installation, I¹ve seen evidence over time of clay ³dusting², thus
> diminishing whatever protection it offered the straw initially.
> I remember reading (in a TLS article?) Kelly Lerner describe a straw
> insulation fire that started (electrical source, as I remember) in the attic
> of a SB house in China. It was not part of the prescribed design, but I think
> it was reasoned that if it¹s good in the walls, why not the attic? I don¹t
> remember if it was loose or baled straw, but either way it is an indicator of
> the fire risk of straw as ceiling, attic or roof insulation. This event gave
> SB a bad name in the region that took time to overcome..
> That said, there are many factors at play. I can imagine reasonably fire-safe
> ways to use straw (with or without clay) as ceiling, attic or roof insulation.
> (Leaving the structural issues out of it.)
> I found the following statement in TLS17 (1997):  "Robert Laporte, timber
> framer and straw-clay builder, commonly uses straw-clay stuffed loose between
> rafters as insulation, with the clay discouraging pests."  I don¹t know if
> Robert still practices this 20 years later. His partner Paula Baker-Laporte
> who is on this list, might be able to say more.
> Also, I¹ve attached an article from TLS38 (2002) ³Bales in My Roof . . . A
> Costly Decision?² that speaks to some of the identified issues.
> Lastly, to the extent that it's relevant, and as far as I know, Rikki is still
> working is Spain (and maybe neighboring countries).
> Martin Hammer
> From:  Gsbn <gsbn-bounces at sustainablesources.com> on behalf of John Swearingen
> <jswearingen at skillful-means.com>
> Reply-To:  GSBN <GSBN at SustainableSources.com>
> Date:  Friday, October 27, 2017 at 6:57 AM
> To:  GSBN <GSBN at SustainableSources.com>
> Subject:  Re: [GSBN] using loose straw insulation in roof
> Quite a long time ago we built a house using bales for roof insulation, with
> site built trusses.The biggest consideration about the insulation value came
> with the numerous large gaps between bales and trusses that needed to be
> filled. The building was near a major farmland highway with large trucks
> passing a few yards away, and the bales did an excellent job of dampening the
> low frequency noise of the trucks. I would consider them again is a similar
> situation, but not for insulation; the cost and difficulty of doing a good job
> is too great, and other good alternatives are available.
> This year we have again been up close and personal with fire, this time
> dealing with melting levels of heat, generating tornado winds in
> concentrations of timber buildings feeding off of each other. We have four
> projects that came within yards of the worst fires, but none of them were
> touched by flames, so we don't have any forensic information to offer.  The
> closest endorsement we've had came from firefighters who came to defend our
> house and we showed them our strawbale cabin with a grassy green roof.  They
> immediately freaked, then looked, pondered, said "no problem" and moved on to
> check out the wood structures.  Nothing like thick plaster and few inches of
> wet dirt to slow down a hot fire.
> Since we're designing a home in the same fire-prone region of Napa, we've been
> looking at the weak links that would make a good plastered house vulnerable.
> In an intense fire, assuming the plaster and roof are good, the weak link is
> heat transfer (and breakage) through windows igniting the interior, and we're
> thinking of mounding sprinklers on the exterior within the window cavity,
> primarily for cooling. We've done this in urban situations when a building has
> been inside the required setback in lieu of a one-hour fire wall This would be
> a slightly different use from preventing the spread of fire--primarily to cool
> the glazing area long enough for a hot wildfire to pass. When firemen show up
> before and advancing fire, they do a lot of wetting. We've installed large
> garden sprinklers on our roofs in the forest, and the firemen are big fans of
> those. Water is their only friend.
> Any thoughts on this?
> John "I'm All Wet" Swearingen
> On Thu, Oct 26, 2017 at 7:13 PM David Arkin, AIA <david at arkintilt.com> wrote:
>> Hi World:
>> Having just taught a few workshops where we measured the density of bales and
>> discussed the possible reasons for a minimum density, this is a timely
>> question.  We actually had some bales that didn¹t pass the minimum 6.5
>> lbs./cu. ft. specified in the International Residential Code (IRC).  Reasons
>> for a minimum density include structural integrity, insulation properties,
>> and fire safety.  The use of loose fill that doesn¹t achieve a minimum
>> density is not supported in this code, but that doesn¹t rule out the
>> possibility that some version might be developed that could achieve similar
>> properties to loose fill cellulose and other materials.
>> For insulation, the IRC and also the IBC specify a maximum flame spread index
>> of 25 and a maximum smoke developed index of 450.  An ASTM E84-98 Standard
>> Test Method for Surface Burning Characteristics test of a Straw Bale in May
>> of 2000 yielded a flame spread index of 10 and a smoke developed index of
>> 350, thus verifying straw bale as a viable insulation material.  Note that
>> this was a test of surface burning of a bale, not loose straw.
>> Curiously, the IBC notes that Cellulose loose-fill insulation only needs to
>> meet the smoke developed index not exceeding 450 criteria, provided it
>> complies with CPSC 16 CFR Part 1200 and CPSC 16 CFR Part 1404, and further
>> stating that Œeach package of such insulation material shall be clearly
>> labeled in compliance with' [these].
>> I¹ve heard some folks in the UK have been experimenting with a chopped straw
>> insulation infill, but the exact parameters of the processing and the
>> resulting fire resistance I don¹t have information on.
>> That all said, I¹ve never done it (put straw in a roof / ceiling), nor do I
>> recommend it, but neither can I say with certainty that it shouldn¹t be done.
>> David A.
>>> On Oct 26, 2017, at 4:57 PM, Bill Christensen <lists at sustainablesources..com>
>>> wrote:
>>> In the ASTM tests that Bruce King coordinated back in 2007, one of the walls
>>> was clay plastered.
>>> Yes, the clay cracked and the straw eventually burned (though the clay
>>> plastered wall did better than cement, we believe because it spent the first
>>> 20 min or so "firing" as in a kiln, and the chemical changes from that
>>> absorbed a lot of the heat).
>>> Loosely packed straw might not fare so well once oxygen can get to it.
>>> We had a problem because the clay plastered wall had a crack on the
>>> exterior, which allowed more oxygen in between a couple bales.  Though we
>>> had stuffed and cobbed those spaces maniacally, the fire followed the path
>>> back through the wall.  We had to cut the test off at 1 hour because of this
>>> - otherwise the clay plastered wall probably would have out-performed the
>>> cement plastered one.
>>> The guys at the testing facility told us that "Everything burns...
>>> eventually.   Everything".
>>> I have to agree with the earlier comments in this thread - loose straw as
>>> ceiling insulation is just asking for problems, whether hit with clay slip
>>> or not.  
>>> On 10/25/17 4:56 PM, Bohdan Dorniak wrote:
>>>> Hi All
>>>> Graeme ­ I¹d be worried about your statement about a ³coating of clay² ­ in
>>>> our fire test of rendered strawbales by CSIRO - done in 2002 ­ the earth
>>>> rendered bale (render about 50mm thick ­ Frank Thomas did the rendering)
>>>> started to show cracking in the render.
>>>> Wondering whether eventually they would burn?
>>>> Other considerations is the weight factor and stronger ceiling structures
>>>> (if using thicker coats of render).
>>>> That¹s my 2 bob¹s worth.
>>>> Bohdan
>>>> From: Gsbn [mailto:gsbn-bounces at sustainablesources.com] On Behalf Of Misha
>>>> Rauchwerger
>>>> Sent: Thursday, 26 October 2017 8:04 AM
>>>> To: Global Straw Building Network
>>>> Subject: Re: [GSBN] using loose straw insulation in roof
>>>> I believe another issue is whether the attic space is vented or not, as
>>>> well as the kind of roofing.  After the Oakland fires, I remember this
>>>> being debated furiously, because the codes require attic venting, and going
>>>> with something like polyisocyanurate rigid insulation without vents was
>>>> controversial.  Obviously the fire danger will increase if air can mix with
>>>> flammable insulation fuel (frieze block vents and ridge vents create a
>>>> perfect means for fully combusting the attic materials) . If it is encased
>>>> and covered with earth on the outside and inside (plaster on the ceiling),
>>>> as in a living roof, we can decrease the flammability factor.
>>>> The Lobo fire that swept through our neighborhood recently came right to
>>>> our friend's straw bale house with only superficial plaster damage on one
>>>> corner.  Of course there are far too many factors to say it was saved
>>>> because of being straw bale or not..
>>>> Then again, if you get a fire like just swept through Napa and Sonoma
>>>> Counties, all bets are off...
>>>> Misha 
>>>> On Wed, Oct 25, 2017 at 1:38 PM, Graeme North <graeme at ecodesign.co.nz>
>>>> wrote:
>>>> This list is a fantastic resource for learned info and is greatly
>>>> appreciated I can tell you.
>>>> The fire thing is scary - there is no requirement in NZ for single
>>>> dwellings to have fire resistant ceiling materials, but we do need to have
>>>> smoke alarms near bedrooms and escape routes.
>>>> The really scary thing is that the fire people here advise that a dry house
>>>> with an open attic with light timber rafters or trusses for roof framing
>>>> will burn from end to end in 60 secs.
>>>> Goodness knows what adding an accelerant like straw (without a good clay
>>>> coating) might do. I would advise against it.
>>>> I would use straw coated with clay  - pretty much a LEM mix - if my
>>>> structure allowed it to happen easily and I was considering it for my own
>>>> house but the work required and extra weight decided against it
>>>> and again recently I considered it on another design but the considerably
>>>> increased extra depth of the roof structure to accommodate it, along with
>>>> the extra cost, work, and weight, decided against it again so I went with
>>>> wool insulation in both cases.
>>>> I am also not convinced that cellulose/paper insulation with borax retains
>>>> it fire rating over time - I have seen examples of old (only a few years)
>>>> cellulose insulation that would not ignite when new,  ignite readily with a
>>>> match and it seems to keep burning quite happily.
>>>> Cheers
>>>> Graeme
>>>>> On 26/10/2017, at 5:36 AM, Bruce EBNet <bruce at ecobuildnetwork.org> wrote:
>>>>> Don¹t you love it when someone else chimes into these discussions ahead of
>>>>> you, and says everything you wanted to say?
>>>>> I sure do.  Thank you Derek and John;  what they said.
>>>>> Bruce King
>>>>> (415) 987-7271 <tel:%28415%29%20987-7271>
>>>>> bruce at ecobuildnetwork.org
>>>>>> On Oct 25, 2017, at 7:56 AM, John Straube <jfstraube at uwaterloo.ca> wrote:
>>>>>> I would echo Derek¹s concerns exactly. Loose fluffy straw burns very
>>>>>> quickly and you may as well say you lost the house.
>>>>>> Adding clay slips will increase the fire resistance to the point is
>>>>>> acceptable, as will dense bales with some sort of clay slip top, but once
>>>>>> you do that, you have a heavy and labor intensive roof insulation.
>>>>>> Cellulose with 20%+ borate treatment is inexpensive, gives good R-value,
>>>>>> is widely available, and is very good at fire resistance.
>>>>>> On Oct 25, 2017, at 10:00 AM, Derek Roff <derek at unm.edu> wrote:
>>>>>> I have a different concern about using straw packed at low-densities in
>>>>>> the roof.  I think that the fire risk increase is much more of a problem
>>>>>> than the decrease in insulation value.  If you have seen flakes of straw
>>>>>> or loose straw burn, you will be aware that they are much more flammable
>>>>>> than standard bales.  Straw flakes are probably about half the density of
>>>>>> a building bale, and loose straw might cut the density in half again..
>>>>>> Losing the roof in a fire usually means losing the whole house¹s
>>>>>> integrity and value.  While enclosing the flakes or loose straw for the
>>>>>> roof in plywood, for example, would help somewhat with fire resistance, I
>>>>>> recommend against design choices that depend on a few things going right
>>>>>> to avoid a catastrophic failure in a fire.
>>>>>> An additional consideration that has been mentioned here before, is that
>>>>>> while bales may be relatively inexpensive, placing them in the roof
>>>>>> requires increasing the size and number of the roof¹s structural
>>>>>> elements, which will likely raise costs more than the amount saved by
>>>>>> using bales instead of other insulation materials in the roof.  Using
>>>>>> lower density straw diminishes that problem to some extent, but straw is
>>>>>> still likely to be significantly heavier than other kinds of roof
>>>>>> insulation, for an equivalent insulation value.
>>>>>> Derek
>>>>>> Derek Roff
>>>>>> derek at unm.edu
>>>>>> On Oct 25, 2017, at 4:34 AM, Rikki Nitzkin <rikkinitzkin at gmail.com>
>>>>>> wrote:
>>>>>> Hi!
>>>>>> I don¹t know if you all remember, but not long ago I asked about the
>>>>>> MAXIMUM density of a SB before it begins loosing thermal propertiesŠ most
>>>>>> people agreed that we should not worry about a bale being too dense...
>>>>>> Now I ask about the opposite question: is there a minimum density?
>>>>>> The other day we were talking about using flakes of straw to insulate a
>>>>>> roof. One of the builders insisted that is was important that the
>>>>>> insulation cavity was filled with highly compressed straw, and another
>>>>>> said that as long as the cavity was properly filled (leaving no big holes
>>>>>> for air to circulate) that the density of the infill is not important, as
>>>>>> the straw (loose or dense, but enclosed in the insulation cavity) impedes
>>>>>> the circulation of air, and that is what insulates.
>>>>>> Can any of you technicians refer me to studies about insulation
>>>>>> properties and how they relate to density? or at least clarify my doubt:
>>>>>> Is it important to highly compact the insulation in the roof? and whyŠ so
>>>>>> I can explain it better.
>>>>>> thanks!
>>>>>> Rikki
>>>>>> ______
>>> -- 
>>> Bill Christensen
>>> http://SustainableSources.com <http://sustainablesources.com/>
>>> http://LinkedIn.com/in/billc108
>>> _______________________________________________
>>> Gsbn mailing list
>>> Gsbn at sustainablesources.com
>>> http://sustainablesources.com/mailman/listinfo.cgi/gsbn
>> *  *  *  *  *
>> Arkin Tilt Architects
>> Ecological Planning & Design
>> 1101 8th St. #180, Berkeley, CA  94710
>> 510/528-9830 ext. 2# <tel:(510)%20528-9830>
>> www.arkintilt.com <http://www.arkintilt.com>
>> David Arkin, AIA, Architect
>> LEED Accredited Professional
>> CA #C22459/NV #5030
>> Director, California Straw Building Association
>> www.strawbuilding.org <http://www.strawbuilding.org>
>> CASBA is a project of the Tides Center
>> "There is no way to peace. Peace is the way."
>> ‹ A. J. Muste 
>> _______________________________________________
>> Gsbn mailing list
>> Gsbn at sustainablesources.com
>> http://sustainablesources.com/mailman/listinfo.cgi/gsbn
>> <http://sustainablesources..com/mailman/listinfo.cgi/gsbn>
> _______________________________________________ Gsbn mailing list
> Gsbn at sustainablesources.comhttp://sustainablesources.com/mailman/listinfo..cgi/
> gsbn
> _______________________________________________
> Gsbn mailing list
> Gsbn at sustainablesources.com
> http://sustainablesources.com/mailman/listinfo.cgi/gsbn
_______________________________________________ Gsbn mailing list
Gsbn at sustainablesources.com

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://sustainablesources.com/pipermail/gsbn/attachments/20171101/cf8adaf9/attachment-0001.html>

More information about the Gsbn mailing list