Water content in green roofs, WUFI Pro

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Water content in green roofs, WUFI Pro

Post by Theasjo » Thu May 14, 2020 12:41 am -1100


I try to simulate the changes in the green roof water content over time (and look especially on the water content in the substrate). I have tried to simulate the green roof both with the green roof material data from the material database in WUFI and the climate data from the climate database in WUFI, as well as used-defined material and climate data (I have added my own material properties for the green roof sedum and substrate. I have also added climate data specifically for the area I am looking at). My problem is that the results do not match the measured moisture results and in general do not make sense. In the simulated results, it looks like the moisture accumulate in the substrate before it becomes constant, even though there are drying periods between the precipitation events, positive solar radiation and higher temperatures. My measured results shows a large moisture content fluctuation over the same time period. It also looks like RH is 100% over the whole year. I clearly do something wrong, but I dont understand what. My questions are therefore:

What do I do wrong? What can be possible reasons for the results I get in WUFI? How can I fix my model?

I also want to double check that the water content (kg/m3) means kg water per m3 substrate?

I attached screenshots of the model build-up, as well as the results from "show graph" and "WUFI-Graph" in WUFI.

Thank you so much for you answer in advance.
water content + precipitation "show graph"
wawtercontent_substrate.JPG (37.58 KiB) Viewed 84 times
Water content WUFI graph
water_contentleca.jpg (30.3 KiB) Viewed 84 times
Model build-up
Profile.JPG (56.94 KiB) Viewed 84 times

WUFI SupportTeam IBP
WUFI SupportTeam IBP
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Joined: Tue Jul 19, 2005 2:50 am -1100
Location: Fraunhofer IBP, Holzkirchen

Re: Water content in green roofs, WUFI Pro

Post by Daniel » Fri May 15, 2020 4:37 am -1100

Dear Theasjo,

what climate location do you use? In our measurements we found between 98 and 100 % RH all year round in the measruement at the bottom of the green roof layers.

So it might be not so unrealistic. However, at dryer regions in Germany we found lower values. So, both is possible. However, if the moisture content cleraly falls below 98 % RH no more normal plant growth is possible.

So, to anwer your question I need some more information.

best regards
Dr. Daniel Zirkelbach, IBP Holzkirchen

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