[GSBN] Straw on edge with stick (stud) frame
mfhammer at pacbell.net
Tue Jul 5 17:27:27 CDT 2016
The system Jacob mentions (invented?) uses ³dense-packed² cellulose
insulation between framing, and tight against the already stacked bales. I
included this in a recent code change proposal for Appendix S Strawbale
Construction in the International Residential Code (IRC). You can see the
added language underlined in the section below. It was approved in April and
will be in the 2018 IRC. (The IRC is the model residential code in the U.S.)
Jacob, and others who practice this method in the northeast U.S. wanted this
explicitly allowed in the U.S. SB code because it was being or they feared
it being questioned or disallowed by building officials.
AS104.2 Purpose, and where required. Strawbale walls shall be finished so as
to provide mechanical protection, fire resistance and protection from
weather and to restrict the passage of air through the bales, in accordance
with this appendix and this code. Vertical strawbale wall surfaces shall
receive a coat of plaster not less than 3/8 inch (10 mm) thick, or greater
where required elsewhere in this appendix, or shall fit tightly against a
solid wall panel or dense-packed cellulose insulation with a density of not
less than 3.5 pounds per cubic foot (56 kg/cubic meter) blown into an
adjacent framed wall. The tops of strawbale walls shall receive a coat of
plaster not less than 3/8 inch (10 mm) thick where straw would otherwise be
Related to this I¹ve used 2x4 studs at 46² (117 cm) with stacked 3-string
bales on edge in between. The studs nestle into the curved-corner joint
between stacks of bales and stacks fit tight at bale ends. A minimal roof
bearing assembly the width of the bales bears on the studs (which are on the
outside wall face only). I call it a ³light post and beam² system.
David Arkin (on this list) and others have used a similar system, but with
TJIs (truss joists¹) installed vertically like studs, with bales stacked
between them. Unlike the system I¹ve used, it has a vertical framing member
both inside and outside (the flanges¹ of each truss joist) and with great
out-of-plane strength, allowing for tall walls or other high out-of-plane
demand designs. It has minimal thermal bridging through the OSB web of each
These systems don¹t do one thing I think you¹re trying to achieve. That is,
adding a layer of insulation to the stacked straw bales. I like that you use
wool between the studs in your system, as long as it¹s packed tightly
against the bales and framing. Trying to avoid uninterrupted vertical spaces
that could be a ³chimney² for fire.
Martin Hammer, Architect
1348 Hopkins St.
Berkeley, CA 94702
On 7/5/16, 8:45 AM, "Jim Carfrae" <jim.carfrae at plymouth.ac.uk> wrote:
> Thanks Bruce
> I¹m adding an extra layer of insulation to keep up with current standards like
> PassivHaus (I don¹t build PassivHaus, but clients like to hear that you¹re
> using similar levels of insulation.)
> Unless anyone else wants to chip in, I¹ll reference Jacob as the originator.
> Jacob, If I continue using a version of this method would you like to be
> credited in the documentation for planning approval etc?
> From: Gsbn <gsbn-bounces at sustainablesources.com> on behalf of Bruce EBNet
> <bruce at ecobuildnetwork.org>
> Date: Tuesday, 5 July 2016 at 16:10
> To: Global Straw GSBN <gsbn at sustainablesources.com>
> Subject: Re: [GSBN] Straw on edge with stick (stud) frame
> I¹ll chime in here just to say that I first heard of the system from Jacob, so
> as far as I know he deserves credit. (Thanks, Jacob!). You can add other
> insulation fairly easily, but generally don¹t need to, other than to plug the
> thermal bridges created by the wood studs where there is no straw.
>> On Jul 5, 2016, at 7:11 AM, Jim Carfrae <jim.carfrae at plymouth.ac.uk> wrote:
>> Hi Dan
>> My interest was mainly to do with combining the structural simplicity of a
>> stick frame with the potential for significant extra insulation, as in the
>> StrawCell example.
>> Does your system involve much additional insulation?
>> In the UK I have been using a 4 by 2 frame with wool as the insulation
>> between the studs. This combines with the straw to reduce the U value from a
>> nominal 0.16 W/m2K for a rendered straw wall down to 0.11 W/m2K for the
>> hybrid wall.
>> From: Gsbn <gsbn-bounces at sustainablesources.com
>> <mailto:gsbn-bounces at sustainablesources.com> > on behalf of Dan Smith
>> <dan at dsaarch.com <mailto:dan at dsaarch.com> >
>> Date: Tuesday, 5 July 2016 at 14:48
>> To: Global Straw Building Network <gsbn at sustainablesources.com
>> <mailto:gsbn at sustainablesources.com> >
>> Subject: Re: [GSBN] Straw on edge with stick (stud) frame
>> Hi Jim,
>> We¹ve been working with a similar system of bales "on end" between 2x studs
>> at 2¹ o.c., with ply/fiber board on the exterior, and have a large addition
>> to an adobe house planned to use it soon, working with Bruce King as
>> engineer. I¹d be happy to chat as well and send details.
>> Dan Smith
>> d s a architects
>> 1107 Virginia Street | Berkeley | CA 94702
>> ph. 510.526.1935 | www.dsaarch.com <http://www.dsaarch.com/>
>>> On Jul 5, 2016, at 6:35 AM, Jim Carfrae <jim.carfrae at plymouth.ac.uk
>>> <mailto:jim.carfrae at plymouth.ac.uk> > wrote:
>>> Hi Jacob
>>> Thanks for the response.
>>> I have been experimenting with a version of this technique myself, and I
>>> principally wanted to find out if:
>>> 1) I was using someone else¹s protected¹ design.
>>> 2) It might feature in an upcoming academic paper, and I wanted to know
>>> who to reference as the originator.
>>> The post that I saw had a photo of a demonstration wall section and a couple
>>> of SketchUp drawings Was that you?
>>> From: Gsbn <gsbn-bounces at sustainablesources.com
>>> <mailto:gsbn-bounces at sustainablesources.com> > on behalf of Jacob Racusin
>>> <buildnatural at googlemail.com <mailto:buildnatural at googlemail.com> >
>>> Date: Tuesday, 5 July 2016 at 13:39
>>> To: Global Straw Building Network <gsbn at sustainablesources.com
>>> <mailto:gsbn at sustainablesources.com> >
>>> Subject: Re: [GSBN] Straw on edge with stick (stud) frame
>>> Hi Jim,
>>> We've been doing this technique for a few years now, in a few different
>>> ways. We coined a term "StrawCell" to describe the hybrid system, a web
>>> search for that term should turn up a few blog posts and videos. I'm not
>>> sure if I was the originator of the post, as others have been using this
>>> technique as well, but I'd be happy to chat further.
>>> On Mon, Jul 4, 2016 at 4:58 AM, Jim Carfrae <jim.carfrae at plymouth.ac.uk
>>> <mailto:jim.carfrae at plymouth.ac.uk> > wrote:
>>>> A couple of years ago details of a bale wall system using bales on edge
>>>> against a stick frame were posted here.
>>>> I can¹t find the original post, and would like to contact the originators
>>>> of the idea.
>>>> Can anyone out there help?
>>>> Dr Jim Carfrae
>>>> Environmental Building Group
>>>> Room 302 Roland Levinsky Building
>>>> School of Architecture, Design and Environment
>>>> Plymouth University
>>>> Drake Circus
>>>> Plymouth PL4 8AA
>>>> 07880 551922
>>>> jim.carfrae at plymouth.ac.uk <mailto:jim.carfrae at plymouth.ac.uk>
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