Using Honeybee_Create Therm Boundaries with ‘indoor’ and ‘outdoor’ inputs, I wonder how we can see the assumptions with regard to the film coefficients?
The thing is, the help mentions both an outdoor coefficient of 26 W/m2.k and Ashrae HoF table, which gives outdoor coefficients of either 34 or 22.7.
My goal is to get the R-Value without air film resistances to define an equivalent homogenous material in EnergyPlus, so I need to take off the air film resistances from the calculated U-Value.
Also, if I set the coefficients by myself, as the model you are using is not based on Therm simplified boundary condition model, I am not sure what kind of equivalent air resistance I need to cut from the total resistance.
It has been a while since I looked back at the therm components but I am pretty sure that the components respect the input if you specify a number for the film coefficient (aka. the convection coefficient of heat exchange). I think the “autocalculate” code based on the ASHRAE HoF table only kicks in when you have specified “OUTDOORS” or “INDOORS” for the film coefficient:
But I know that the film coefficient only accounts for ~half of the heat exchange that happens at the boundary of the construction. The other half is the radiant heat exchange, which THERM autocalculates based on the emissivity and the view factor. I don’t know if there’s an easy way to get therm’s autocalcualted value for the radiant exchange coefficient out of THERM. That might be more of a question for the THERM forum.