Below Ground Climate

[Carl_Brookes]

Hi,

I'm looking to model a below ground basement which will house a space with a high level of respiration activity. We want to get a representative climate file for the ground, i.e. the external side of the wall construction being assessed. I have a reasonable understanding of the annual ground temperature profile at, say, 5m below ground but I'm less certain of the annual RH profile. Is this something I can only generate in WUFI Pro, or is there an alternative source for such data? Any guidance would be helpful.

Many thanks,

Carl

[Christian Bludau]

Dear Carl,
if I calculate a construction in the ground I use temperatures from literature, for example this one:

Temperature below ground (x-axis: meters, y-axis: temperature)

erdreichtemperatur.jpg (75.62 KiB) Viewed 20009 times

From that I generate a sine-curve for the temperature.
You probably have to find something what is corresponding with your location.

For the relative humidity i set constant 99 or 100% as we assume that otherwise nothing will grow.
The catch the influence of the temperature exchange between the construction and the soil I build a layer of soil on the outside of the construction, thickness about 0.5m.

If I have a construction with additional ground water, I generate a climate file (wac) out of that, containing rain every hour.

Christian

[Alberto Morales]

Hi Christian,

1- Any chance to get these temperature values from the graph in an excel or txt file?

2- then if I have understood correctly the "mateiral information" in wufi database about the two types of soils that you added, the weather climate associated to each one are:

2.1 for the case Soil 'Christian' FSP , the weather file .wac should contain three parameters TEMPERATURE (graph above for example), RH (constant 100%) and RN =1000

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2.2 for the case Soil 'Christian' DIN , the weather file .wac (outdoor climate-blue line image) should contain only two parameters TEMPERATURE (graph above for example) and RH (constant 100%)

Captura de pantalla 2022-10-20 001950.png (18.6 KiB) Viewed 13693 times

3 see photo attached. Should I place the .wac file for ground there (blue vertical line)?

Captura de pantalla 2022-10-20 001129.png (33.59 KiB) Viewed 13693 times

4 what don't I understand is how the lines below are defined in the .wac file? Do they correspond for west and south orientation? where do those numbers (-1e11) come from or what do they mean?

-1e11 Longitude [°]; East is positive
-1e11 Latitude [°]; North is positive
-1e11 HeightAMSL [m]

5 I guess that the temperature value is quite high (20 degrees see screenshot above) for a soil and I should put the value(s) from your graph or the right one for the soil in my location (variable for the whole year or constant value depending if I have data available). Am I right?



Regards

[Christian Bludau]

Hi Alberto,

1- Any chance to get these temperature values from the graph in an excel or txt file?

I do not have them, but I also do not need them. You can easily create a user-defined sine curve in WUFI indoor climate from the max and min value for the needed depth. For example in 4m you can use 7.5 °C (blue, April) as min and 11.5 °C (pink, Oct) as max. You can create the sine from that with the following parameters: mean value 9.5 °C and amplitude 2K. To add this in a climate file, you can calculate for one year and export the curve.

2.1 for the case Soil 'Christian' FSP , the weather file .wac should contain three parameters TEMPERATURE (graph above for example), RH (constant 100%) and RN =1000

yes, right, Soil Christian FSP can be used with liquid water, the DIN one only takes in account moisture transport by diffusion.

3 see photo attached. Should I place the .wac file for ground there (blue vertical line)?

yes, right. Further use "Basement" as setting for heat transfer coefficient.

4 what don't I understand is how the lines below are defined in the .wac file? Do they correspond for west and south orientation? where do those numbers (-1e11) come from or what do they mean?

-1e11 means, that no value is given here. A numerical value is necessary here. That is used instead of 0, as 0 would be a valid input.
Position and Height is only needed, if radiation has to be transformed to other values. So for soil these values are not necessary.

5 I guess that the temperature value is quite high (20 degrees see screenshot above) for a soil and I should put the value(s) from your graph or the right one for the soil in my location (variable for the whole year or constant value depending if I have data available). Am I right?

yes, right

Best regards
Christian

[Alberto Morales]

Hi

thanks once again and apoligise i did not realise you replied.

then what I have to do is:

1- create a sine curve for soil at 4 m with april minimum value and october maximum value and amplitude 2 K
2 - export it and place it in the left part of the wufi interface as an exterior climate
3- heat coeff , I have to select basement although i have no basement in the reality because I have slab on ground instead. Am I right?

Questions:

1- why do I take values at 4 m for soil temperature but in wufi I define a layer of 0,5 m?

2- for the case "Soil DIN", do i have to only to take into accoun the temperature (do it in the way you explained using sine curve) and RH at 100% and that is all?


Regards

[Christian Bludau]

Hi,

1- why do I take values at 4 m for soil temperature but in wufi I define a layer of 0,5 m?

I took the values at four meters only as an example. Use the depth which corresponds with your construction. Building in a layer of soil is necessary to also account for the interaction between the component and the soil. But because the soil parameters may difer from the one in the database, I would not use a 4m layer. Further this will lead to alonger calculation time.

2- for the case "Soil DIN", do i have to only to take into accoun the temperature (do it in the way you explained using sine curve) and RH at 100% and that is all?

yes, thats right.

Christian

[Alberto Morales]

HI,

Thanks again for you feedback.

1- Which depth of my construction do you mean? Which layer of my slab on ground would correspond that depth?

Regards

[Alberto Morales]

Hi,,

1- How do you export step by step the sine curve created in "indoors climate" inside wufi?

Regards

[Christian Bludau]

Hi Alberto,

1- Which depth of my construction do you mean? Which layer of my slab on ground would correspond that depth?

That would be the depth your assembly is exposed to.

1- How do you export step by step the sine curve created in "indoors climate" inside wufi?

Use WUFI Pro, there you just can export that easy:

1. Calculate something
2. Goto Outputs -> ASCII-Export...
3. Select "Interior Air Temperature (Interior Climate)" and "Relative humidity (Interior Climate)"
4. Define output file
5. Press OK

Christian

[Alberto Morales]

thanks a lot

Finishing this topic and consultation- i get what you see in the images in my case

soil ("DIN" for diffusion & "FSF" for ground water/water stagnant)
gravel 200 mm
insulation (EPS, density 30kg/m3) 300 mm
Concrete 100 mm (modeled with 3 layers top middle and bottom from fraunhofer institute database)
PE foil (in one case above concret in other case below concrete)
impact insulation (ROCKWOOL)
Flooring (HARDWOOD)

two cases: PE foil above or below concrete
Interior climate two cases : iso 13788 and EN 15026 to see differences

IO VS EN.png (135.31 KiB) Viewed 13435 times

exterior climate see txt files next message

- what i get at the top of the concrete is that PE foil above concrete has higher RH than PE below concrete (75 vs 60%, dot lines) with ISO 13788 with manual calculation (using the calculation method in the center of the building below ground: L/B, d/B, vapor permeability of the materials,...).

Using WUFI and DIN soil/iso 13788 i get at the top of the concrete 75 % for PE foil below concrete but 67% for PE foil above concrete ,... see image below

Using WUFI and DIN soil/EN15026 i get 60 % at the top of the concrete for PE foil below concrete and also 60% for PE foil above concrete after 20 years but being higher until then,... see image below

1- Why is the reason of that?

ground graph.png (46.85 KiB) Viewed 13387 times

- for EN 15026, after 20 years I get same values of RH in the concrete for PE foil above or below,
2- Does it make sense?

- for ground water vs vapor diffusion I do not see any difference in RH in the concrete and slightly in the insulation (apart from the bottom of the insulation) and no difference at all with or without gravel (caìllary break) and no difference at the top concrete for diffusion, ground water + gravel and ground water + no gravel.
3- does it make sense?


4- which material do you use as a fabric filter between soil and gravel ? i saw that people use geotextil but i dont find anything similar in the database. which one do you recommend? becasue PE foil is is used as a vapor barrier or dpm in the higher parts of the ground but not between soil and gravel. Correct me if i am wrong in the concepts of the layers


these are my conclusion:

- vapor diffusion/PE foil below concrete: 300 mm EPS (vapor-tight exterior insulation) keep top of insulation dry so no moisture from soil reach the top of insulation. PE foil doen't moisture from indoors to reach the insulation so concrete ends up at the same moisture level (RH) than inddor climate

- WHEN PE foil is above concrete, RH concrete is below than with PE foil above concrete because no moisture from indoor reach the concrete and no moisture from soil reach concrete due to 300 mm EPS

- EN 15026 get lower RH in insulation and concrete due to lower RH indoors vs ISO13778 Humidity class 2 (+4 g/m3). See graphs from inddor climate in WUFI. RH indoor reach a peak of 90% (75% average) for ISO 13788 while EN 15026 (maximum 65%) meaning unrealisting moisture for indoor climate in a building.

- Manual and WUFI calculation for vapor diffusion - PE foil below concrete and ISO 13778 Humidity class 2 (+4 g/m3) get the same RH at the top of the concrete (around 75%) and this value is below the RH critical for concrete, 85%.

- Manual and WUFI results (RH at top of concrete) contradict each other when PE foil is installed above concrete.

- EN 15026: The presence of ground water does not have impact in the RH of the concrete maybe due to 300 mm EPS (EPS:close-cell insulation so it is resistant to water and moisture. This means that it does not absorb them) because non-existent layer of gravel (capillary break) have hardly an influence in the result regarding to RH in the concrete although in the reality it has.

5- How can WUFI take into account the effect of gravel as a capillary preak?


Let me know if i am right and make my conclusion sense in general

thanks in avnce and apologise for all this

[Alberto Morales]

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[Alberto Morales]

hi,

any feedback or comment please?

regards

[Daniel]

Hi Alberto,

sorry, but we cannot solve such specific topics in detail within the Forum. If you need more detailed assistance, please buy a support package.

If you have short, specific questions, please limit them to one question per post. However, it might take a while to answer. Please understand, that we have very limited capacities.

Daniel