ISO 15099

Our expert software WINISO® has been extended by the calculation according to the American standard ISO 15099. The “ISO 15099” add-on is available for this purpose.

With the add-on “ISO 15099” the relevant calculations of Ufr-, Ueg- and Ucg-calculations according to ISO 15099 and NFRC can be carried out. Once the calculation is complete, you can generate the printout specifically for ISO 15099 and receive a list of the materials used. The calculation results with the corresponding Imperial units are also specified.


For our expert software WINISO® for the calculation of heat flows, thermal bridges, isotherms and Uf values according to EN ISO 10077-2:2018 the add-on “Humidity” is available for the calculation of relative humidity, vapour diffusion and condensation water failure.

The following evaluation modes are available with the “Humidity” add-on:

Relative humidity fields

The display provides information about the quality of the profile/component. The darker the spots in the profile, the greater the relative humidity, i.e. the risk of condensation. The calculated value Psat is the saturation vapour pressure at the point in the component. It is temperature-dependent and indicates the maximum amount of water the component can absorb in Pa at the respective point.

Pi is the partial water vapour pressure at the respective point. The partial pressure is adjusted by the boundary conditions and the heat transfer in components and cavities. If the partial pressure exceeds the saturation pressure, the component is “supersaturated” at the point in consequence condensation water precipitates.

Vapour diffusion flow fields

It shows how much water in g/m*d flows through a component. The water vapour flow runs through a component in the same way as the temperature curve. This means that the water vapour flows along the partial pressure gradient from high to low. The resistance number μ is decisive for the diffusion current through a component. The larger the number, the more impermeable the building material is.

Condensation loss

If the partial pressure Pi exceeds the saturation vapour pressure Psat, condensation occurs in the profile. Common causes are low temperatures and low diffusion resistance figures μ of the individual components. Places where condensation precipitates are marked in blue.


Isotherms are curves of the same temperature that show the quality of a component with regard to the loss of condensation and the risk of mould. The 10 °C and 13°C isotherms are striking for condensation and mould formation.


The U value of a frame, called Uf value, indicates the heat transfer through the area of the frame and is based on DIN EN ISO 10077-2.

The heat transfer is expressed in watts per square meter and Kelvin. The Uf value of a frame profile is determined automatically in WINISO®. The glass structure is replaced by a calibration panel. After the calculation a scalable frame and the result appear in the view. The sides of the frame can be moved manually. This changes the calculated Uf value.


The length-related heat transfer coefficient, called Ψ value, indicates the heat transfer through the edge seal for windows and is based on DIN EN ISO 10077-2.

The Ψ value is given in watts per meter and Kelvin. The Ψ value of a frame profile is automatically determined in WINISO®. The glass structure is replaced by a calibration panel for the first calculation run. The original glass pane is restored for the second calculation run.


A measure of the thermal quality of a component. The higher a U-value is, the more heat passes through a component. In WINISO® you have the possibility to calculate the linear U-value on the basis of the selected place, or to calculate the U-value (total).

heat flow

The heat flow indicates how much heat flows through a construction per time. The cause of the heat flow is a temperature difference. The heat flow through the enveloping surface of a heated building is proportional to the temperature difference between inside and outside.

Heat flow fields in WINISO® show where the improvement potential of the component in terms of heat transfer lies.


The temperature factor, called fRsi factor, is a criterion for the risk of mould growth with a wall connection (connection of a window to the adjoining wall) and is based on DIN 4108-2.

The factor should reach at least 0.70 so that no mould can develop under standard conditions. The fRsi value is determined at the point of the minimum surface temperature.