[Ferro List] dougs fc parabolic video

[Doug Lacy]

Hi Peter -
It is only one layer of lath for the walls.
It is trowelled on.  The reason I have been reluctant to pursue spraying is because the ten mix a day hand trowelling produces 500 square feet and that is a fair amount of cement to finish, cover-up and take care of.  It seems too problematic to do a larger area in a day.  Now, however, I am considering Progressive Cavity spray rig because this last 40 bag job I finished this last weekend and early last week revealed some issues.  It was a beatuiful design, big seashell light fixtures, nice sculputral details and a flowing Celtic kind of look and all, but it was a difficult struggle, to say the least, to keep on top of the finish while mixing and directing a couple of new helpers.  I had to be everywhere at the same time.  

If I had sprayed the wall, a larger area would have been done in a shorter amount of time, but then I could set down the spray gun, and float the right finish.  Yes, a spray rig is a good idea.  Not that I would do more area in a day so much as it is that it would help us concetrate more time on finishing the shell just sprayed rather than splitting up the workers.  

I think the heat transfer through the WWM would not be significant because the transfer of heat to the shell, because of the direct contact to the non-insulating aspect of the fill, would equalize the temperature.  This would not be the case if the steel was going through EPS. 

 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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> Date: Sun, 20 Apr 2008 09:59:38 -0400
> From: tfe at sover.net
> To: list at ferrocement.net
> Subject: Re: [Ferro List] dougs fc parabolic video
> 
> Hi Doug,
> Great posts, great info, thanks!
> Couple of questions:
> One layer only of lath on your WWM blocks?
> Mortar trowelled or shot on?
> Have you ever calculated the heat transfer throught the WWM? I'm 
> thinking of using plastic form ties between outside and inside layers to 
> minimize this, seeing as I'm in Vermont.
> All the best
> Peter
> 
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