Insulated interzone surfaces (e.g. attic floors, skylight well walls) are considered as part of the building envelope by ASHRAE 90.1 (or other energy codes/standards like the Canadian NECBs).
OSut methods like rsi and resetUo rely on standard condition surface air film resistances, ideally harmonized with OpenStudio and EnergyPlus values.
Have noted 2 issues concerning interzone surfaces:
- OSut (interzone) surface air film resistance constants do not align perfectly with OpenStudio
- OpenStudio calculations are not aligned with EnergyPlus', when it comes to interzone floors/ceilings
Issue 1 should be an easy fix. Issue 2 is on the OpenStudio SDK side of things - see enhancement request for SDK filmResistance. Until a fix is introduced, a decision must be made to either harmonize with OpenStudio or EnergyPlus. For very well insulated constructions, the difference isn't that significant. More noticeable for poorly insulated cases (e.g. existing buildings in cold climates).
Insulated interzone surfaces (e.g. attic floors, skylight well walls) are considered as part of the building envelope by ASHRAE 90.1 (or other energy codes/standards like the Canadian NECBs).
OSut methods like rsi and resetUo rely on standard condition surface air film resistances, ideally harmonized with OpenStudio and EnergyPlus values.
Have noted 2 issues concerning interzone surfaces:
Issue 1 should be an easy fix. Issue 2 is on the OpenStudio SDK side of things - see enhancement request for SDK filmResistance. Until a fix is introduced, a decision must be made to either harmonize with OpenStudio or EnergyPlus. For very well insulated constructions, the difference isn't that significant. More noticeable for poorly insulated cases (e.g. existing buildings in cold climates).