Therm 7.6.01-Boundary Condition Library-Relative Humidity

[Luca Caruso]

Hello, 

I am currently using Therm 7.6.01 so as to assess the effect of `thermal bridges in buildings.

May I ask you why the relative humidity needs to be inputted in Boundary Conditions (simplified) as shown in the picture? Can it be useful for the assessment of superficial/interstitial condensation? if yes how can affect the calculations?

Thanks in advance

Luca

[yal...@gmail.com]

Hi Luca.

You are correct and if you input the relative humidity the results display will show interior surfaces that are below the dew point temperature.

[Luca Caruso]

Hi Yal,

thanks for your reply.

If you told me the RH would be related to internal condition, which conditions should I have to assume the external outdoor temperature as Ext Boundary Condition? According to the ISO standard we have to assume the lowest monthly average DBT for outdoors and inside the prescribed indoor temperature, at 50% RH: the RH you mean relates to indoor or outdoors? Because for THERM if I change the RH for an internal boundary condition it will change even the one I've created for external one. I don't know whether it is a bug of the software or I am missing something: the manual is not updated and in the previous version this option wasn't available.

Best

[yal...@gmail.com]

I haven't encountered the software changing the RH values when I change for one side or the other. Seems to be working fine for me - Maybe LBNL folk could look at that for you.

I think 50% RH is the Therm default but it can be what you want to analyze or the interior conditions for the problem you are solving for. You can generate the temperature and RH conditions with ISO 13788 or whichever standard you are referring to however in Therm there is no correlation between the indoor RH and outdoor RH. It is only an input to determine the DP temperature so the surface temperatures lower than the DP can be displayed.

[Luca Caruso]

Hi, for DP do you mean Dew point?

Best