Error/simulation results + Sources

[Alberto Morales]

Hi,

the Wufi 2D file attached shows a jamb detail. I have a few questions:

1- where should the 1% rain be placed? see image please

2- how should I model the air infiltration from indoors? where should I placed it? see image

3- if you enter 1% rain then, do we need to calculate the strength of that source or WUFI does it automatically for each grid element? does Wufi transform L/m h from climate file to kg/m s to each grid element? how does wufi distribute that 1% rain individually between all grid elements selected in the interface of WUFI 2D (tab sources/sinks)? if we have 3 different exterior boundary due to the different characteristic/properties of the external surface, which one should we associated to the "fraction of rain Load"?

4-regarding to the strength, which "fraction" should we define for each case/climate,...? if BC is kg/m2 s (rain incident), where does this data come from? field measurement? which are the rain measurement field unit typical? if we get BC from field measurements, how do you split this into your different grid elements? because each grid element need to have an individual file or, do you divide your measurement by the ratio area of the grid element/total area and you apply to each grid element? how do you determine/define the L and whole area (A) of the source (I mean in what you base to know the extension of both dimensions in your wufi2D grid and their correspondence with the reality)?

sorry about all these question but I find it that there is a lack of info or at least I am not able to find it.

5- after simulating the model (without any source), the simulation does not finish the whole year. i was reading the most recent post where poeple had the same issue and I tried to follow your recomendations or I hope to have done that. do you find any improvement I can do in the computational parameters? if I use WUFI Graph it is showed a large peak in the water content what suggested some problem. maybe I dis not defined very well some materials. i define the dissecant typical from spacers as a soil because the chemical composition is SiO2, glass as mu 999999 and porosity 0,01, air layer as a air layer without additional moisture capacity, sealant as a foam form Japan databes,...maybe the error come from here. any advice please?

I sent the file to support wufi because it was too large

thanks in advace for your help and patience

[Alberto Morales]

mes y medio.png (25.64 KiB) Viewed 64514 times

mes y medio 2.png (42.02 KiB) Viewed 64514 times

As you can see my simulation stops after one monh and a half when theta and phi starts being zero. I have been reading all post about this issue in WUFI 2d and I follow all of them changing convergence criteria, changing NSW, simplyfy the model, etc etc, I also change the material but, what is the sense of doing that if you real material are other? how can you extrapolate the results?

I rhink it would be good if a guideline for user about this type of error, possible causes, how to solve it (including inamges or steps), etc etc would be useful because this problem has been happening a lot since long time ago for many people.

Regards

[Christian Bludau]

Hi,
according to your questions:
1) in my eyes there is no special need to place a rain source in there or or are you concerned that water may run in next to the window connection?
2) why would you model an air infiltration here. This should be build air tight.
3) you do not have to calculate anything. WUFI is taking 1% of the rain which is available in your boundary condition, already related to the orientation and is spreading that on the area you define.
4) I do not completely understand the question. The fraction of 1% is from the ASHREA Standard 160. The rain is usually measured as rain on a horizontal surface measured in liter or kg per m² and hour. With that, the orientation and the rain WUFI calculates the rainload for the surface:

Code: Select all

Rainload = Rain(horizontal) * (R1+R2 * Wind velocity)

R2 is a factor for the height and R1 is a factor for the inclination, so its 0 for vertical surfaces and 1 for inclinations <90° (in this case R2 is 0).
From this Rainload the 1% is taken.
5) It is often not clearly pointable, what causes an convergence problem. Can be a material, climate condition, etc. I would recommend to simplify your construction especially for the window and frame. I would replace them by a single material with effective values for vapor diffusion and thermal conductivity instead of building them from eg. glass and air. Further check in the WUFI2DMotion, if there is a peak in water content at the moment before the calculation stops. If so, try to change the material at this position.
Last I recommend to switch on the adaptive time step control in the computational parameters as well as in the enhanced settings try, if it helps to switch on the rational interpolation of the sorption isotherm.

Christian

[Alberto Morales]

JAMB SIMPLIFIED.zip

please see attached the detail

I added a coat in front of the window frame to see if supersaturated window frame or insulation does not happen, is it correct to do that in the simulation?


a building is never built perfectly airtight.

i thought I should place a moisture source of e.g. 1% (ASHRAE 160) just in case (as the wore scenario) in the connection jamb/wall because it is possible to find small holes/cracks, poor workmanship works/old house etc etc that makes water enter. a building/house does not stay as-built along the years

[Christian Bludau]

Hi Alberto,

I added a coat in front of the window frame to see if supersaturated window frame or insulation does not happen, is it correct to do that in the simulation?

the coat you are talking about is the metal deck? You can that this way, but this is completely the wrong material, its something like corrugated sheets and they have a very low sd-value. I would use something like aluminum here. WUFI 2D calculates much better if you do not built in tight layers at the outside but considerate them as an sd-value in the boundary condition. So i recommend to do that here. During cold times there will probably form dew water in the air layer on the back side of the metal which also may cause convergence problems.

a building is never built perfectly airtight.

yes, I agree

i thought I should place a moisture source of e.g. 1% (ASHRAE 160) just in case (as the wore scenario) in the connection jamb/wall because it is possible to find small holes/cracks, poor workmanship works/old house etc etc that makes water enter. a building/house does not stay as-built along the years

yes, than do that this way, but keep uin mind that 1% of rain may be quite a lot depending on the yearly rain load at your location.

Christian

[Alberto Morales]

apologise, i though it was the right file. it should be a silicone resin coat

please see the new file

new jamb.rar

(265.31 KiB) Downloaded 612 times

coat resin.png (36.28 KiB) Viewed 64496 times

[Christian Bludau]

yes, thats correct this way, but I would use a sd-value in the boundary condition instead of building it in as a layer, as that calculates much faster. If you do so, switch off the rain for this surface, as the sd-value does only affect the RH and not the rain.

Christian

[Alberto Morales]

thanks for answer, i tried this option but i am still having problem and getting peaks in water content, woul you take a quick look please and see what it is wrong? i tried all strategies but...unless no worries I will keep going

Jamb.zip

(379.84 KiB) Downloaded 635 times

[Christian Bludau]

These peaks in your water content are not convergence errors. They are related to rain events. The aerated clay bricks have quite a high a-value, so they are sucking up the rain water quite fast. In the total water content that shows an high influence. Have a look on the water content of the wooden frame for example, there are no peaks. Or compare with a calculation without rain, that should not show these peaks.

Christian

[Alberto Morales]

hi again,

i have been reading this post

viewtopic.php?f=15&t=794

and I am confused now because the coating that I try to model for the wood window frame (to avoid water can be absorbed/penetrating) can be also defined following the Guideline for modeling water-repellent treatment of a façade

what is the most accurate/right way to do it? defining a sd value in the surface transference coeff (coating) in Weather/climate and switching off the rain or following Guideline for modeling water-repellent treatment of a façade?

Regards

[Christian Bludau]

Hi Alberto,
the method you use for simulation depends on your treatment / coating.

If you have a water tight coating then it is sufficient to take that in account as vapor barrier or on the outer surface better as a sd-value in the boundary conditions. If modeled as a sd-value you would have to switch off the rain.

If you have a water-repellent treatment, where a certain amount of rain can still be absorbed, that can not be expressed as a vapor barrier. In this case you use the guideline for the water-repellent treatment. Here the a-value and µ-value have to be adapted.
https://wufi.de/en/service/downloads/#w ... _treatment

As the water uptake for the wooden window frame is usually quite low and about zero with a coating, I would to model that with a sd-value. The water-repellent treatment is typically used for mineral materials like bricks in historic wall assemblies.

Christian

[Alberto Morales]

thanks a lot. very very helpful

[Alberto Morales]

Results.png (65.3 KiB) Viewed 64461 times

LAST.png (41.44 KiB) Viewed 64460 times

what I observe from the results is that the moisture absorbed in the window frame is transmited to surrounding areas but what I do not understand why is the Relative Humidity BRICK Coating/Brick+water repellent model is different to Relative Humidity BRICK no Coating/Brick+water repellent (i mean coating in the window frame is the difference between both models),

do oyu know why?

another thing i the peaks/jumps observed in Relative Humidity BRICK no Coating/Brick+water repellent and Relative Humidity CAVITY CLOSER no Coating/Brick+water repellent- and Relative Humidity EXTERNAL INSULATION No coating/Brick+water repellent

do you know why?

[Christian Bludau]

Hi Alberto,

what I observe from the results is that the moisture absorbed in the window frame is transmited to surrounding areas but what I do not understand why is the Relative Humidity BRICK Coating/Brick+water repellent model is different to Relative Humidity BRICK no Coating/Brick+water repellent (i mean coating in the window frame is the difference between both models),

another thing i the peaks/jumps observed in Relative Humidity BRICK no Coating/Brick+water repellent and Relative Humidity CAVITY CLOSER no Coating/Brick+water repellent- and Relative Humidity EXTERNAL INSULATION No coating/Brick+water repellent

can you please show me, what positions / areas you are using in detail for evaluation?

Christian