I wonder if/how thermal bridging of joints/egde between constructions should be included in the U-value of the construction?
Example of such joins are corners, wall joints with roof or ground constructions, window (frames) in walls, balkonys, columns in a wall or areas in front of the internal ceilings when the ceiling is penetrating the wall insulation. These losses can be calculated using the standard "ISO 10211 - Thermal bridges in building constructions" among others.
If these effects of connections should be included into the U-values of the construction, how should the loss be spread between the two different constructions?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5912 thumbs up
December 6, 2024 - 9:35 am
Infiltration issues should NOT be included in any U-value calculation, same with thermal mass issues. Infiltration levels should be a separate input into your energy modeling software.
Sonja Kildishev
Dipl.-Ing.WSP Sverige AB
December 9, 2024 - 2:48 am
Thanks for your reply! There seems to be a missunderstanding. I am not talking about infiltration, but about the extra thermal transmission through geometrical thermal bridges at juncions. More information can be found on this pages:
Definition and effects of thermal bridges [Passipedia EN]
Thermal bridge - Wikipedia
If the extra losses of the junction with two diffent constructions is considered, please tell me how it should be included in the calculation.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5912 thumbs up
December 9, 2024 - 1:53 pm
You account for those by calculating the whole assembly U-value. See Appendix A in ASHRAE 90.1-2010. You don't need to account for the junction of two different construction assemblies.