[Ferro List] dougs fc parabolic video

[Doug Lacy]

Oakridge has a program for creating computer models for thermal performance on alternative home desigs.
If I were plastering by myself, I would only do a half a wheel barrel at a time and then plan on making a second coat later so you are not rushed to get it perfect by yourself.  Also, carefully measure out the area you are going to plaster and do half of it, and finish it all the way and then do the other half.  That way you are not having to go in overdrive.  The mix in the wheelbarrel will last longer than the mix on the wall.

I have thought about the one man operation a lot.  4 wheelbarrels may be too much for a  day with one guy but, doing the half batches that will plaster 25 square feet.  If you break that down into two bites at a time, that is 12.5 square feet or an area of about 3 feet by 4 feet.  That is about as large of an area I would attempt in one bite.  It would still be a little rush to get that shell all done but it it is going to be two coat, meaning another skim the next day or so, then you can quickly brush that area with a fresh slip of cement and water

Another key plan for making the one-man operation work, or just a smoother operation for the regular 4 man crew, is to make ready two dry mixes of the cement slip.  Whip up the first right when you start to plaster you first 12 square foot patch.  And the second right befor you do the other.  Usually we mix a big bowl of cement powder and water when we start.  The problem with that is that you end up adding more and more water to the slip to make it brushable.

When you brush on freshly made cement slip over freshly applied plaster, it does the most good because it lets you brush plaster that would otherwise be way too wet for a standard wet brush or float, you still have to wait a bit, and it makes a very hard finish while wipping out the surface pores.  

Trying to do this with an old watered down slip starts to cause water runs and dusty flaky finishes.  Even if you were doing a scratch coat, I would use the slip to help the thinshell keep its moisture, plaster over it and apply another one.  A big waste of cement it may seem, but if is done right it really helps one man show.

 Cellular Concrete has some engineered charts for 'R' value at given densities.  It is at the Litebuilt site from Australia.  The 28 lbs per cubic foot mix is r 2 plus per inch.  I am not sure the clay and straw would do better but not sure.

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> Date: Mon, 28 Apr 2008 09:35:02 -0400
> From: tfe at sover.net
> To: list at ferrocement.net
> Subject: Re: [Ferro List] dougs fc parabolic video
> 
> Hi Doug,
> Thanks for the info.
> Yes, modeling the thermal performance is hard. What program are you 
> referring to, from Oakridge?
> A friend of mine recently built a Yurt-type structure with 12 inch walls 
> made from a straw-clay insulating mix, which probably performs similarly 
> to foamed concrete; the thermal performance was great. Even in the depth 
> of winter (25 below), the unoccupied house maintained a constant 65 
> degrees with hardly any fluctuation, with one small fire a day in the 
> woodstove.
> When finishing the surface, what are you looking for? What kind of 
> timing is involved in the finish treatment?
> Is there an issue with the mortar staying workable long enough to trowel 
> on the whole batch?
> I'm mostly working alone without helpers--wondering how the timing will 
> work.
> Peter
> 
> Doug Lacy wrote:
>> Hi Peter -
>> (snip)
>>
>>  The thermal performance of the wall shell by itself is a complex thing to model.  I really worried about the first house and how it would compare to its counterpart for a winter season.  It did well by using only one small tank of propane instead of two as did the standard insulated masonry counterparts.  Someday we will be able to invest in a thermal model program from Oakridge National Lab.  I think the thermal performance will surprise a lot of people on how well it can conserve heating and cooling.  If it fell short on insulation for a cold climate, the EIFS system on the exterior would take care of it.  EPS foam or sprayed foam on the outside and then a thin fiberglass mesh and polymer modified cement shell.
>>
>> Doug
>>
>>   
>>
> 
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