U-Value of a ventilated façade

[Haalsaad]

Dear Delphin-Team,

I am simulating a highly-ventilated facade (wall + ventilated air gap + cladding). I want to calculate the U-Value of the facade from the temperature difference and the heat flux through the construction (1D simulation). Which approach is the correct one to create a TotalFluxHeat output?

a. [Single] at the interior surface (Boundary flux)
b. [Single] at the first element adjacent to the interior air
c. [Mean] at the whole construction (Field flux)

Follow up question: I am using an [AirChange] and a [LongWaveRadiation] sources to simulate the highly-ventilated façade. From the above listed options, if I was to use option (c) and extract the mean value of heat flux from all the elements, should I export the heat flux from the whole construction (wall + ventilated air gap + cladding), or should I only select the elements of the wall and ignore the air gap and the cladding? Thank you very much for your help!

[fechner]

Hello,

Normally a) is ok. For a 1D construction 'Single' is Ok. For 2D you have to use 'Mean'.

Method c) makes no sense for my point of view. A U-value should reflect the heat losses of a room through a wall. A heat loss means a loss from the room air. This leads to the fact that you have to use the heat flow over the inner boundary.

[Haalsaad]

Thank you very much!