Thermal bridges: f_Rsi and annual loss

Calculate the temperature factor f_Rsi of the undisturbed area of an element and the annual loss through a linear thermal bridge with a known ψ. Free, no account.

The f_Rsi factor of the plain element

Element type

Material names and element types are the entries of the Romanian catalogue, as they appear in the regulations.

Thermal transmittance U of the element (W/(m²·K))

f_Rsi = 0.916; the threshold is 0.80, so it is met.

Loss through a linear thermal bridge

ψ of the bridge (W/(m·K))Length of the bridge (m)Degree-days (K·days/year)

Loss: 7.61 kWh/(m·year), that is 91.3 kWh/year over the whole length.

You enter ψ yourself, from the detail sheet. The bridge catalogue and the 2D calculation are in the calculation software.

How it is calculated

f_Rsi is calculated from U with the internal surface resistance of 0.25 m²·K/W used for condensation, and the threshold of 0.80 comes from Mc 001-2022, §2.1.4.

The annual loss through a linear bridge is estimated indicatively as ψ × degree days × 24 / 1000, in kWh per metre per year, then multiplied by the length of the bridge.

You take ψ from the detail sheet or from the calculation. The thermal bridge catalogue and the 2D calculation are in the calculation software.

The full report

The bridge catalogue, the ψ calculation per detail and the f_Rsi check at corners are in the calculation software, with an account. The trial lasts 30 days, with no card.

Create an account See the software (RO)