[GSBN] Straw Bale Insulated Ceiling
John Swearingen
jswearingen at skillful-means.com
Tue Feb 4 16:54:24 UTC 2014
For the "igloo" method, we did do a bale vault in the desert. One source
of concern we had was about vapor being able to escape to the outside,
since the latex roof membrane was directly on the bales. After plastering,
the bales contained a lot of moisture, and the house wasn't occupied, and
with the building at an equilibrium with the outside temperature, little
drying was happening, and we went running to Dr. Straube for advice. He
suggested we turn on the air conditioning, and that created enough
temperature differential to drive the vapor to the outside. I'm not sure I
would do a roof anywhere but the desert without some sort of venting at the
top of the bales.
An interesting feature we noted in our monitoring was that the vapor moved
around in the bales in the vault quite a bit following the heat of the sun.
We've observed this in walls, as well--vapor moves freely around inside
the bales following temperature conditions, particularly from the sun. One
thing this means is that if you have a condensing surface at the top of the
bales (often the case), and a source of excessive moisture (air leak), heat
will drive vapor to the top of the wall where it may condense and cause
damage.
Nice bulidings, Jorge. On the first house, what's the ceiling? It looks
like wood slats...
John "I go Igloo" Swearingen
On Tue, Feb 4, 2014 at 6:45 AM, Van Krieken <vankrieken at gmail.com> wrote:
> Feile
>
>
> 1. As well as in the walls, the gaps bettween the bales on the roof have
> to be carefully closed with loose straw. Its a easy task, but it takes time
> to be really well done (as everything else, I guess! :-)
>
> 2. When you put the bales on the roof (and afterwords the top wood
> structure) you'll notice that its not really very flat (as the walls
> aren't), so, if you just plaster it you'll find many places with 5, 6, 7 or
> even more cm of plaster. Thats very heavy. This is one of the reasons I
> prefer to use LECA mixed with the lime (just enought to agregate the LECA),
> because we can put 5, 6 or more cm without a height problem. I do not thing
> you need to put it on the bottom side of the bales, the ones in contact
> with the OSB, but before puting the bales I spray OSB and bales with a
> generous borax dilution, let it well dry and then put the bales. You may
> also wanto to use a special anti-fire OSB in the roof.
>
> 3. The fllor. because we need thermal mass, we use a 20 cm limecreet
> (stones, 1/2 lime and 1/2 cement). Then 5 or 6 cm of sand mixed with 50%
> lime and 50% white cement (just a little water on it). When is still fresh,
> we apply the powder: white cement and natural ochre with a tiny little bit
> of red (iron sulphate). In that particular case we used 700 g white cement
> + 150 g ochre + 10 g of red. After, you should apply some wax or natural
> vernish (we use form www.ecospaints.com ). Thats it.
>
> I like the "igloo" method (complete surrounded by insulation) to make a
> house. Its looks to me that is much more easy and fast, and with no thermal
> leeks. We are also building several houses with cork, using the same
> "Igloo" procedure. You may see one here (we have build this one in 12 days,
> 6 persons (140 m2).
>
> http://www.queridacasa.com
>
>
> Hope you enjoy! All the best
>
> Jorge Van Krieken
> Portugal
>
>
>
> l
>
> On Tue, Feb 4, 2014 at 10:35 AM, Feile Butler <feile at mudandwood.com>wrote:
>
>> 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 <vankrieken at gmail.com>
>> *To:* Global Straw Building Network <GSBN at sustainablesources.com>
>> *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 <feile at mudandwood.com>
>>> *To:* Global Straw Building Network <GSBN at sustainablesources.com>
>>> *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 <%2B353%20%280%29%2071%20930%200488>*
>>>
>>> *M: +353 (0) 86 806 8382 <%2B353%20%280%29%2086%20806%208382>*
>>>
>>> *E : **feile at mudandwood.com*
>>>
>>> *W:www.mudandwood.com*
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--
John Swearingen
Skillful Means Design & Construction
2550 9th Street Suite 209A
Berkeley, CA 94710
510.849.1800 phone
510.849.1900 fax
Web Site: http://www.skillful-means.com
Blog: https://skillfulmeansdesign.wordpress.com
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