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Thermal break in conc. wall

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I’m working on a passive solar residential project where a large concrete mass wall is an important part of the program.  It’s an internal wall, running through the centre of the structure, 10’ in the basement, 10’ main floor, and 11’ upper floor, 32’ long.  The design is driven first by thermal storage requirements, and there are several options, but one that we probably will not go with got me thinking and talking to my colleagues yesterday. 

 

This is in the Tetons (NW Wyoming), zone D, and most of the E-W shear is going to end up in this wall.  A cheap(er) way to go would be to build the wall continuous from the footing, but we would require a thermal break between the basement and main floor.  How would anyone go about this?  If we poured the basement portion then capped it with 2” compression-rated blueboard, we could transfer the lateral across the break with the bars, but there are significant vertical floor & roof loads all the way up.  Compression in the blueboard would not be a failure mode, and I assume it would (almost) all take place at the time of the pour, but what happens when a big roof GLB point load is applied 2, 3, 4 weeks into the concrete cure?  It’s a similar problem to compression perp. to grain in wood, except that with concrete things are brittle.  Dead loads on the roof are big (green, sod), as are live loads (Pg = 120 psf).  I’m not aware of anywhere this is addressed in ACI 318, but it’s the sort of idea that could have a code stipulation that reads:  No.  Never.  Period.

 

Any ideas?  Thanks.

 

Gordon Goodell

Driggs, ID

 

 


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