BuildSysPro.IBPSA.ThermalZones.ISO13790.BaseClasses.OpaqueElements

# .BuildSysPro.IBPSA.ThermalZones.ISO13790.BaseClasses.OpaqueElements

## Information

This model calculates the heat flow by solar gains through each opaque building element k. The heat flow is given by

Φsol,k =Fsh,k Isol,k αk Rse Uk Ak - Ff Φr,k

where Fsh,k is the shading reduction factor, Isol,k is the solar irradiance per square meter of surface area, αk is the dimensionless absportion coefficient for solar radiation of the opaque element, Rse is the external surface heat resistance of the opaque element in (m K/W), and Ak is the area of the opaque element.

The form factor between the building element and the sky Ff is set to 1 for roofs and 0.5 for external walls. The extra heat flow due to thermal radiation to the sky is given by

Φr,k =hr ΔTsky Rse Uk Ak

where hr is the external radiative heat transfer coefficent which is approximated as 5 ε W/m2K (where ε is the emissivity for the thermal radiation of the external surface), and ΔTsky is the average temperature difference between the external air temperature and the apparent sky temperature.

## Revisions

- Mar 16, 2022, by Alessandro Maccarini:
  First implementation.

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