Hi,
I suffered from this question as well. And I was hoping someone from EP+ support team could make the output variables are more clear for the user to use.
I am gonna talk a little bit here as far as I know, I searched a lot, and I found out that this questions are a little bit tricky.
In order to investigate building fabric/envelope losses, what I did is also using the ideal air load system of a simple building (one zone, with window, external wall, roof, floor, door) setting up in EP+.
what I used for the envelope losses, I am looking at these variables: (according to the DesignBuiler reference:http://www.designbuilder.co.uk/helpv1/Content/Calculation_of_DesignBuilder_Output_from_EnergyPlus_Report_Variables.htm)
- window heat losses= window heat gain- window heat loss- transmitted solar radiation.
About window heat gain and losses, it has been explained in the EP+ reference, however, to be honest, I am not fully understand, and from my understanding there should either heat gain or heat loss, but when I did the simulation that I found out, both of them are non-zero values at the same time step.
Surface Window Heat Gain Rate:
The total heat flow to the zone from the glazing, frame and divider of an exterior window when
the total heat flow is positive.
For a window without an interior shading device, this heat flow is equal to:
? [Surface Window Transmitted Sollar Radiation Rate (see definition, above)]
? [Convective heat flow to the zone from the zone side of the glaziing]
? [Net IR heat flow to the zone from zone side of the glazing]
? [Short-wave radiation from zone transmitted back out the window]
? [Convection to zonee from window frame and divider, if present]
Surface Window Heat Loss Rate [W]:
The absolute value of the total heat flow through an exterior window when the total heat flow is
negative. (See definition of â??total heat flowâ?? under â??Surface Window Heat Gain Rate,â?? above.)
- wall/roof/floor heat losses: surface inside face conduction heat transfer rate/w
Hope this helps.
Nancy