Sources

[manexi]

Hello,

I'm now trying to simulate flaws on my walls. I was told I should do this by using sources on my model, but I cannot find info in the WUFI help on this.

I know I can use Heat, Moisture and Air sources, but when should I use these and how should I define them? (Source types, what's the associated boundary for?, how do I define airchanges [1/h]...?)

For example, what's the difference between the definition of an airSource and a moistureSource? Are they equivalent?

Do you have an example where sources (moisture, air) are being used?

Well, I know it's a lot of questions, but if you had an article on this or an example it would greatly help me.

Thank you for your time!

Best regards,
Manexi.

[EoinDIT]

Hi,

I'm having similar problems with creating a moisture source to imitate a failure in a damp proof membrane in a roof construction. When I run the video no moisture appears to be created where I have placed the moisture source in the grid. I'm using 100% fraction of rain associated to the outside boundary, a flat roof with a climate file attached to it. Any help on this would be much appreciated,

Thanks,

Eoin

[Christian Bludau]

Hello Eoin,
are you sure there is rain in your outer climate file? Go to analysis in the climate window and check that.
Furthermore Wufi2D will end up the calculation if a material is supersaturated, what for sure will happen, if you put 100% of rain in your construction. Please check in the calculating window, if there is a value for T and RH or everything is zero during the iterations.
Christian

[EoinDIT]

Hi Christian,

Thanks for getting back to me, I was working on the model quite a bit last night and its all running fine now. I am however confused as to the best way of imitating a leak or failure in a roof membrane. If the source I have is 1mm x 1mm, located just underneath the roof membrane and it receives 100% of the rain would that not recreate the scenario of a 1mm hole in a roof membrane? Sorry if I am just not getting this calculation method.

Thanks,
Eoin

[Daniel]

Hi Eoin,

if you use one singel grid element you'll get maximum the amount of rain into your structure which falls on an aerea of the grid element width and one meter length (maybe reduced to free saturation ect. if chosen under clipping). If you have a hole in the membrane the amount will be similar - only difference: if the absorption capacity in one hour is lower than the offer, the remaining rain water will run off...

In reality the water film will penetrate the hole and a much higher amount of water can run beneath the film - not only locally. But in this case you need no simulation to know that the structure will fail.

So what exactly do you want to simulate? To use the sources in an adeuqate way you need to have an idea about the amount of rain water whiche penetrates the hole - this amount you cannot simulate - its part of your input data...

If you have a certain leakage I'd propose to run the simualation even in 1D and use a homogenuous source!

best whishes
Daniel

[EoinDIT]

Hi Daniel,

I'm trying to simulate the drying out ability of different wall and roof build ups when a roof membrane fails. ie a parapet detail. The structure is Cross Laminated Timber and I am comparing using different types of wall build ups to see which will allow for the timber structure to dry out and which will not.

Originally I simply increased the water content in the CrossLam but would like to re-create the scenario in which a roof is leaking and using the climate file and a water source to imitate it.

I have until now placed the source within the CrossLam and have been unsure as to what % fraction of rain to input. To put it simply I want a source to simulate the amount of the water that would ingress through a leak in the roof to reach the Cross Lam structure.

On a side note I have tried looking into creating a source file but have not found much information on it.

Thank you for any help you can give,

Best Regards,
Eoin

[Daniel]

if you have a wooden flat roof (vapor tight sealing) with rain water leakages you will always get some damages (at least locally) - so it's not a good idea to simulate permanent rain water leakages in that way.

If you have such a leakage and following a high water content you have to seal it and then you can check ho long the drying period is. Therefore please start with a high moisture content in the exterior wooden sheating - for example 30 % by mass - or a value according 2 kg/m²...

Then you can check if additional drying measures are required or not.

For a wall which is vapor permeable to the outside you can use the 1 % rainwater source - but not at one single grid element but over the whole hight of the wall!

best regards and happy Easter
Daniel