Thermal bridging – 90.1 2019 PRM Appendix G

This section applies to:

ASHRAE 90.1 2019 PRM Appendix G

If the Coefficient (simple) approach is selected in VE preferences:

Proposed building: users can enter thermal bridging coefficient values for each construction on the APcdb > Thermal bridging tab. The default setting is zero. For climate zones 0-3 the value should be set to zero.
Baseline building the thermal bridging coefficient values for each construction on the APcdb > Thermal bridging tab are fixed to zero and un-editable.

If the Psi value (detailed) approach is selected in VE preferences:

Proposed building: users can pick default or enter custom Psi values for each construction on the APcdb > Thermal bridging tab.

Random thermal bridges are drawn in the model and assigned a Chi value via ApCDB > Random thermal bridge type.

For climate zones 0-3 the Psi & Chi values should be set to zero.

Baseline building: the APcdb > Thermal bridging tab is not editable. Psi values are set to zero.

Random thermal bridges drawn in the model will be removed in the baseline building.

Caution: regarding Psi value dimensional conventions; users should ensure that custom values entered respect the dimensional convention set in VE preferences. In the USA (ASHRAE 90.1 but not ASHRAE RP 1365) the external plane convention is typical.