U-Factor Surface

[Reem Madkour]

Hi All,

When defining the boundary conditions should I be assigning the exterior surfaces as the u-factor surface or the interior surfaces? Does it matter or depend on whether I'm in a heating or cooling climate?

In the example attached I'm modelling the affect of a balcony slab to the overall exterior wall u-value. I've taken the exterior boundary all around the balcony slab and assigned it to u-factor surface "Wall" to calculate my u-value over the entire section. Please let me know if you think this is accurate. 

Kind Regards,

Reem 

[Robin Mitchell/LBNL]

Generally the U-factor tags are applied to exterior surfaces. See the NFRC THERM / WINDOW Simulation Manual on our web page (the very first PDF link)

https://windows.lbl.gov/therm-documentation

Here is an example image from that document: