Capillary flux between the indoor and the roof

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WEI LI
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Capillary flux between the indoor and the roof

Post by WEI LI » Tue Apr 26, 2022 11:56 am -1100

Hi experts,

My roof structure has the perlite board as the innermost layer. I know that perlite board is capillary-active materials. However, since it is directly facing the indoor environment, I do not expect it would absorb any water liquid.
When I plot the capillary flux density at the interface between the perlite board and the indoor, it shows that there is more or less some water uptake. Please see my attached pics.
My question is:
Is that physically possible? Materials absorbing water liquid by capillary forces from the indoor?
Thank you in advance.
interface.png
interface.png (17.91 KiB) Viewed 96 times
water uptake.png
water uptake.png (69.47 KiB) Viewed 96 times

Thomas
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Re: Capillary flux between the indoor and the roof

Post by Thomas » Wed Apr 27, 2022 3:04 am -1100

WEI LI wrote:
Tue Apr 26, 2022 11:56 am -1100
Is that physically possible? Materials absorbing water liquid by capillary forces from the indoor?
Hi WEI LI,

no, unless rain is hitting the surface there should be no capillary flow across the component surface.

However, considering the fact that the flows you see are of the order 1e-12 kg/m²s, I should think these are just numerical rounding residuals. After all, a moisture flow of 1e-12 kg/m²s is so microscopically small that at this rate it would take 1e9 seconds or 32 years to transport one single gram of moisture through 1 square meter of surface area.

Best regards,
Thomas

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