Window: u-value LBT 1.4


I have recently converted to the LBT 1.4 from the Legacy version. Although I assigned the input parameters the same, the heating and cooling results are very different from each other. Do you think this might be because LBT 1.4 uses a u-factor (single glazed: 5.82) while the Legacy uses a u-value (single glazed: 300) when assigning window custom construction?

I assume some default values are also different since the results are not matching. I used OpenStudio in both cases for energy simulation.

Do you think this difference in the results in the LBT 1.4 and Legacy is due to the ground construction that I haven’t assigned? I left blank in the Legacy the ‘expFloorEPConstruction’ in Honeybee-Set EP Zone Construction while I think it assigns a default value in ‘ground_subset’ in the HB ConstructionSet component.

Hi @berrakbalci ,

Those differences you point out about the single pane glass are not very meaningful since the 300 that you see in Legacy just refers to the glass without any air films while the LBT U-Factor includes air films on either side of the glass (you can see this is where most of the thermal resistance comes from since glass is much more conductive than air). Long story short, those two glass panes are basically the same.

Also, you should go through the energy modeling tutorial videos on the LBT plugin:

The later videos there show you how to construct an energy balance, which tells you where exactly your energy use is coming from.

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Hi @chris

Thank you very much for the tutorials. I have already watched them and constructed my new energy simulation script accordingly. However, the heating and cooling load outputs still differ from my Legacy version results.

I created custom construction the same as my Legacy inputs. So, I think the difference between these two versions might be because of the HVAC defaults. Do you have any suggestions for that?