Condensation issue

[Romain Ravenel]

Hi everyone,

I'm writing to ask for your help with the ‘Show surface condensation potential’ option. I've looked at the documentation and the video illustrating the use of this display with a metal frame, but unfortunately I haven't found the answer to my question. My various searches on the forum were in vain.
Specifically, I'm attaching the Therm model screenshot (version 7.8.16) I'm studying. The colour codes are as follows:

 - Orange, pink and green: Future rigid or blown-in insulation.
 - Yellow: Existing insulation.
 - Grey: Concrete structure.
 - Beige: Air space.
 - Purple: Fixing materials for future windows (Purenit).

The aim is to identify potential condensation problems in this construction detail. Unless I'm mistaken, it seems to me that THERM is not at this stage in a position to determine whether there would still be a condensation problem inside the wall (between the grey concrete and the green insulation, for example). In the examples I've seen on both forum and THERM website, THERM only identified problems on the inside of an internal wall. Is this correct?
If this is confirmed, do you know of any other software that would be able to meet my needs? I've heard of Glasta and Wufi, and I sometimes use the Ubakus site ( https://www.ubakus.de/u-wert-rechner/? ) but it doesn't allow me to take such complex walls into account.

Thanks in advance for your help !

Romain

[Romain Ravenel]

Hi,

I'm taking the liberty of relaunching the post in the absence of a reply for the moment.
Does anyone have any ideas?

Romain

[Zugur Rakhmanov]

Hi Romain,
If as I understood correctly your aim is to determine the value of a dew point temperature and show the isotherm of that temperature in your detail.
If so you should first determine the temperature of a dew point using  Td = T - ((100 - RH)/5)  formula or simply use the calculator https://www.calculator.net/dew-point-calculator.html?airtemperature=23&airtemperatureunit=celsius&humidity=50&dewpoint=&dewpointunit=celsius&x=Calculate/
 For your case the dew point temperature will be 12 °C.
Next you can set display results of calculation in the Calculation --> Display Option window. For the min temperature and interval of isotherm step set the value which would not miss in the diapason of the temperatures of your calculating, for max temperature set the value of the dew point temperature. Next click OK-->OK.
It will show a single isotherm. Where that isotherm will come out to the interior surface you will get potential condensation.

Kind regards,

Zugur

Вт, 6 мая 2025 г. в 20:56, Romain Ravenel <romain....@gmail.com>:

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[Collin Robinson]

Romain, 

THERM can accurately simulate material temperatures and isotherms, but doesn't simulate air and moisture movement. If interior moist air can leak into the assembly, you could use the isotherm of the dewpoint temp of that air (12°C) to determine risk. If there is an interior air barrier then it's not as much of a concern. 

Condensation risk and mold risk evaluation is more complex. If all surfaces are nonporous and moisture-insensitive it is simpler, but in my location all assembly materials being nonporous is rare. For example, an absorptive material like wood, whose surface is at the dewpoint temperature of the air next to it, won't necessarily show condensation. The wood's moisture content will increase but the wood's MC must be very high and have no substantive drying periods for mold to grow. Although the simple WUFI I use (ORNL) is basically one-dimensional geometry-wise, with some coaxing it shows the time effects of air and moisture movement in the assembly, throughout the year. It can also show 1% of rain leaking through the water barrier. Sometimes I will make a WUFI simulation of a particular area of a section that I want to look at in greater detail. I found WUFI pretty straightforward to learn. Best of luck!

Collin

[Romain Ravenel]

Hello,

Thank you all for your very pertinent answers!

Romain