Hello
starting from this interesting topic
https://discourse.ladybug.tools/t/how-are-the-energy-balance-items-calculated/2235/8
I have decided to go more in detail with EPlus.
I am actually interested in perform manually quick checks of the results from Energy plus, in order to be sure if the outputs could be reasonable or not, using steady state equations taken from the main law of Technical Physics (conduction across element, convection, heatbalance, thermal loads).
So far,
I am able to manually verify the convection load due to natural ventilation (sensible and latent) and infiltration.
I am aware of how each variable affects the other when dealing with air heat balance.
However I donâ??t know exactly how to deal with heat balance of the envelope, and In particular i havenâ??t found useful info regarding the way eplus calculates the U value listed in the idf reports and the unique u-value films provided (surface resistance) since in a dynamic simulation they should vary over time.
Having said that, I have been doing some permutations in order to verify that [Surface Avg Face Conduction Rate/ (Outdoor DBt-Zone Mean Air Temperature)] gave the overall U value , which I have manually calculated under the condition of the absence of solar radiation. The results were almost 2-3 times than the expected. Even subctracting the effect of the indoor/outdoor Surface Convection Heat Transfer, i still get results that are too high.
I am quite sure that I havenâ??t fully understood which are the Eplus variables that define the heat balance per each opaque and transparent component.
If you may have any publications/articles that have addressed this topic and you can share with us It would be highly appreciated. I have checked many times the Eplus I/O reference and Eng. reference without solution.
Thanks in advance.
Luca