Thermal bridges, windows U value calculation

Hello,
I have a general question about pollination possibilities with the Rhino plugin for building energy balance calculations
a) can thermal bridges be included in the calculation and can their length be automatically determined from the model, e.g. building corners, window perimeter? psi value for internal or external bridge dimension type?
b) how detailed is the U-value of windows calculated - only as a total U-value or can it also be formed by taking into account the proportion of window profile/glazing, profile width, profile/glazing parameters, type of thermal brake (aluminum or warm edge)?

Best regards,
Andris

Hi @andris ,

Sorry for the late response. To answer your questions:

No, this type of calculation usually requires some relatively sophisticated finite-element modeling in order to do accurately. Furthermore, EnergyPlus expects any thermal bridges to be accounted for in the assembly R-values that you feed it (meaning that it’s at a level of detail beyond what the Pollination opaque material layers can handle).

If you are looking to calculate assembly U-values using dimensions of thermal bridges, your best bet is to model them in LBNL THERM. The Legacy Honeybee plugin had a connection to THERM, which may be useful for this. We are hoping to eventually port this functionality over to the LBT Grasshopper plugin (and maybe the Pollination Rhino plugin). But, for now, working with THERM (and optionally the Legacy Honeybee plugin) is your best bet.

Right now, the Rhino plugin does a pretty detailed job modeling all of the heat exchange that happens between Window gas gaps (including the convection of the gas in the gaps and the radiative exchange across the gaps). However, there is currently no way to specify detailed frames for the window constructions but supporting frame definitions is high on our priority list. You will know when support for frames has been implemented when you see this GitHub issue is closed.

FYI, the U-values that you see in the Rhino plugin will pretty much always be for a 1 meter by 1 meter window but EnergyPlus will use your detailed window geometries to compute the U-value on a window-by-window basis. When we implement support for frames, I think we will also add some Grasshopper components that let you calculate the assembly U-values for window dimensions other than 1 meter by 1 meter.

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