Suspended floor over open crawlspace.

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rrenaud
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Suspended floor over open crawlspace.

Post by rrenaud » Thu Oct 28, 2021 9:46 am -1100

I am trying to model a wood framed floor in a historic building that is above a open crawlspace. The floor consists of Harwood flooring, rosin paper, wood plank sheeting, and 2x10 wood joist framing. This have a 2' crawl space open on all sides.

We have set the inclination to 0 degrees, set shortwave radiation absorption to "No absorption/emission" sine the exterior surface faces straight down and turned off the Adhering Fraction of Rain to "No absorption" for the same reason.

The interior environment is 72degrees +/-2 degrees and 40% RH +/- 5% RH varying over the period of a year as a sine curve.

The problem is regardless of insulation specified for the joist spacing, regardless of where we locate a vapor retarded in the assembly (or also not having one) or locating an air barrier on the exterior (Or also not having one) the RH goes to 100% at the bottom of the insulation. The outside climate is Charleston, SC, USA.

Am I missing something or is this beyond the programs ability to simulate.

Christian Bludau
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Re: Suspended floor over open crawlspace.

Post by Christian Bludau » Thu Oct 28, 2021 7:02 pm -1100

Hi rrenaud,

you can simulate such crawlspaces with WUFI. Also the way you set the boundary conditions sounds ok.

there may be several reasons for the high RH at the bottom of the insulation. Is there a vapor tight layer bellow the insulation? Is the heat transfer coefficient at the bottom 0? Do you start with a high initial moisture which may be redistributed to the cold side?

Can you describe the construction as well as the boundary conditions more detailed?

Christian

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