[GSBN] Fire resistance of unrendered straw bales

Fri Aug 3 19:29:40 UTC 2018

Hello Pete Walker, All:

We recently completed a 34,000 sf (3,160 M2) mixed use warehouse / office building, with straw bale insulated walls on the second and third floors of offices.  The project was completed and occupied a few months ago:  https://www.arkintilt.com/salvaged-materials-mahonia    https://www.arkintilt.com/mahonia-mixed-use-building (finished photos coming soon).  

1)      Has anyone else had similar experiences? If so, how did it work out?
Worked out great!  We probably had a similar number of bales (±750) within our building at any given time, with some on palettes and some in the walls, before the plaster work started.  
We hosted a series of three weekend workshops; the first weekend we trained 15 leaders for the second weekend, which had around 60 people, and the third weekend focused on clay plaster.  These Facebook posts are 9 months old now (hard to find), so here are links:
https://www.facebook.com/pg/CASBACaliforniaStrawBuildingAssociation/photos/?tab=album&album_id=1480355395380273 
https://www.facebook.com/CASBACaliforniaStrawBuildingAssociation/videos/1480998491982630/
https://www.facebook.com/pg/CASBACaliforniaStrawBuildingAssociation/photos/?tab=album&album_id=1482517535164059
https://www.facebook.com/pg/CASBACaliforniaStrawBuildingAssociation/photos/?tab=album&album_id=1479606938788452

2)      Has anyone had experience of straw bale buildings catching fire during construction? If so, how did it work out?
Thankfully, no. I’ve heard tell of fires burning loose straw on the ground and up the surface of a wall, and then burning themselves out or being put out, with little or no damage.  Other than a one-room studio, a good number strawbale projects have survived wildfires (post-construction): 
https://www.facebook.com/CASBACaliforniaStrawBuildingAssociation/ (yesterday’s post, re: a project near Redding, CA)

3)      What other fire protection measures have you experienced? Are your walls/bale stockpiles covered by a fire protection layer during construction, before rendering?
‘Straw Management’ was a major emphasis throughout the workshops / installation of bales, and a part of all of our bale-raisings.  We have a document that addresses this specifically, including:
	- fire extinguishers and/or water hoses at the ready
	- a crew specifically dedicated to raking and relocating loose straw
	- absolutely no smoking or flames 
	- electric and hand tools only
Our bales were stockpiled within the building, in stacks on palettes, without protection (other than the roof).  Could someone have snuck into the building, started a fire and potentially burned it down? Perhaps, but that’s true of nearly every building during construction.  

4)      Does anyone have data/information on fire performance of unrendered straw bale walls?
Yes.  Attached is a report on a fire test of unplastered bales.  We submitted this to the City Building Official when they inquired about how the straw met flame spread index and smoke developed index limits for commercial insulation.  Anyone who has tried to burn a straw bale knows how difficult it actually is.  

5)      Any other words of advice?
Ensure that the insurance company is aware of the straw construction, and will cover a fire during construction.  Having a plan for fire protection and straw management during installation is important; perhaps the fire safety consultant would want to assist with the drafting of this?  Limiting the number of unplastered bales could be a hassle, but if it’s the only path available, it can probably be made to work, albeit with programming issues.  We started plastering some walls before others had their bales in, so it could’ve worked for our project, but with issues, and it was a whole lot faster and easier to not have this restriction.  

Hope this helps, 

David Arkin / ATA & CASBA

> On Aug 3, 2018, at 7:14 AM, Pete Walker <P.Walker at bath.ac.uk> wrote:
> 
> Hi
>  
> I am writing on behalf of a leading straw bale builder in UK who has run into concerns from a fire safety consultant concerning exposed straw bales during construction. The consultant is happy to accept the fire performance of load bearing straw bale walls once rendered, but is concerned that the exposed (unrendered) straw bales present too high a fire load risk during construction. To limit this risk the consultant is requiring that the 2 and 3 storey bale walls are rendered in stages as the construction progresses (in sections of around 250 bales per time), rather than all in one go after completion of all the bale walls (around 750 bales in total), as is more usual practice. This will cause significant programming issues for the project.
>  
> Therefore, I am writing to enquire:
> 1)      Has anyone else had similar experiences? If so, how did it work out?
> 2)      Has anyone had experience of straw bale buildings catching fire during construction? If so, how did it work out?
> 3)      What other fire protection measures have you experienced? Are your walls/bale stockpiles covered by a fire protection layer during construction, before rendering?
> 4)      Does anyone have data/information on fire performance of unrendered straw bale walls?
> 5)      Any other words of advice?
>  
> many thanks and best wishes
>  
> Pete Walker
>  
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Arkin Tilt Architects
Ecological Planning & Design

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Thank you!

David Arkin, AIA, Architect
LEED Accredited Professional
CA #C22459/NV #5030

1101 8th St. #180, Berkeley, CA  94710
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