[GSBN] Straw Bale Insulated Ceiling

Tue Feb 4 10:35:24 UTC 2014

Thanks to all of you for your replies

Danny and Jorge - you both mention the difficulty in packing the gaps between bales effectively. I suspected that might be a problem - so good to get your practical experience in the field.

You both also say that sealing with plaster is the best way to achieve fire rating. Bohdan mentioned a fire test from Germany - does anyone know who the author is so that I could look it up? Or does anyone have information on thicknesses of plaster required to achieve various fire ratings?

Bohdan - I understand why you are questioning why they don't just use a natural fibre batt. I think a big part of the reason is ethos. The clients have access to plenty of locallly produced straw bales - which are as close to an unprocessed but effective insulation product as they can get. I suppose another option would be to look at accessing and cleaning a load of sheep fleeces. But if that is not an option - then they need to buy a manufactured product. Only sheep's wool is produced in Ireland (which would be a good option), but it is manufactured in the exact opposite corner of the country. Anything else (wood fibre, hemp) would have to be imported from Europe.

But, as you say, if we end up using an excessive amount of timber to support the bales, then that is not a truly sustainable solution either. It's always a balancing act! As I said in the previous email - we're just exploring the option at the moment.

Jorge - I thought that was interesting that you used the LECA with the lime - I presume you did it to have achieve the maximum insulation values. But with an entire bale doing the job for you, do you think that was an excessive detail? Or was there another reason I missed?

I also have to say I LOVED the look of the house when it was entirely enclosed with bales - great to see bale walls AND roof.

And as an aside - I love the colour of the floor too, particularly the yellow. Was that an earth floor? Did you have very pale earth on the site and pigment it up with ochre? It's a really beautiful finish.

Cheers

Feile

  ----- Original Message ----- 
  From: Van Krieken 
  To: Global Straw Building Network 
  Sent: Monday, February 03, 2014 10:44 PM
  Subject: Re: [GSBN] Straw Bale Insulated Ceiling

  I used strawbales in the roof, with a special atention to fill the voids between the bales (its quite time consuming). We sealed the bales with a hidrated (or aerial) natural lime mixed with expanded clay aggregate.
  You may see some pictures here: http://strawhouses.carbonmade.com

  All the best

  Jorge Van Krieken
  Portugal

  On Mon, Feb 3, 2014 at 4:09 PM, Danny Buck <dannycbuck at msn.com> wrote:

    Our experience here in New Mexico was that the roof structure gave us a lot of voids between bales that were very challenging to pack. If it is a true attic with a flat open surface to work off of, that would be different.

    The surface of the bale that is accessible to air (oxygen) is best sealed with a plaster. 

    Danny Buck
    Daniel Buck Construction, Inc.
      ----- Original Message ----- 
      From: Feile Butler 
      To: Global Straw Building Network 
      Sent: Monday, February 03, 2014 2:57 AM
      Subject: [GSBN] Straw Bale Insulated Ceiling

      Hi All

      I have clients who are considering insulating above the ceiling with straw bales. They have a large attic which could easily accommodate the bales and plenty of outbuildings, so they don't need the attic for storage.

      I have never detailed a straw bale ceiling before, but would like to explore the idea. 

      One of my main concerns is fire. Is it enough to encapsulate the bales within plasterboard/clayboard on both sides (top and bottom)? If we want to deck out the floor above the bales, would it be enough to coat them in a lime or earth plaster before building up the floor above them? Is there any data out there about the behaviour of straw bales in ceilings that I can show the building control officer, particularly with regard to fire?

      Any advice on or experience of straw bale insulated ceilings would be very welcome.

      Thanks

      Féile Butler
      MRIAI B.Arch Dip. Arch Conservation Grade III

      Mud and Wood

      Grange Beg, Skreen, Co. Sligo, Ireland

      T:  +353 (0) 71 930 0488

      M: +353 (0) 86 806 8382

      E : feile at mudandwood.com

      W:www.mudandwood.com

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