WUFI

However I did not understand the next "If in your case the heat flow can be expected to be predominantly upwards or downwards, you may choose the respective options. Otherwise, the next best option is probably to use a mean value.". Could you please put an example?


Hi Alberto,

in the case of ...

Hi Alberto,

the science behind those numbers is this: Air at rest has a thermal conductivity of about 0.025 W/(mK) and a vapor diffusion resistance factor of µ=1 (by definition). However, the air in an air gap of a building component is usually not completely at rest. Temperature differences across ...

Dear David,

WUFI does not directly output the ice content since this has not been of major interest so far. However, you can compute the ice content from WUFI's standard output.

For liquid water and frozen water to be in equilibrium, they must have the same vapour pressure. Usually, at ...

Hallo Philipp,

zu den ersten beiden Fragen:

1) Die beiden Angaben zum w-Wert des mineralischen Außenputzes sind identisch und nur in verschiedenen Einheiten angegeben. 0,00167 kgm2 s 0.5 (pro Wurzel sekunde !) sind gerade 1/60 (= 1/Wurzel(3600)) des w-Werts 0,1 kg/m2 h 0.5 (pro Wurzel stunde ...

Hi David,

the highest water content tabulated in the moisture storage function (the moisture content corresponding to relative humidity = 1, or 100 %) is the free saturation wf . This is the number to be used for generating the liquid transport coefficients. Free saturation results when the ...

does WUFI always uses this formula (1 + 0.01*temperature) to determine the ice content, regardless of the material properties?

Dear Jan,

WUFI uses this formula for all materials since it is independent of any material properties. It is based on the fact that in thermodynamic equilibrium the ...

Dear Jan,

WUFI takes into account that water contained in small capillaries does not freeze at 0°C but at some lower temperature which depends on the capillary radius. In a given grid element, water in large pores may be frozen while at the same time water in smaller pores is still liquid. WUFI ...

Hi Walter,

the driving rain coefficients determine how much rain will reach the surface. They include everything that happens before the water hits the surface.

For example, the "normal rain" is measured with respect to a horizontal receiving plane, the driving rain is measured with respect to a ...

Hi Benoît,

the details of the air infiltration source are as follows:

For each time step, WUFI determines the lowest temperature occurring in the region covered by the source.

If this temperature is higher than the dew point temperature of the indoor air, nothing happens. If it is lower ...

Hi Benoît,

I will check with the programmers about how the air infiltration source function has been implemented exactly, regarding the temperature evaluation and the moisture release within the source region.

Kind regards,
Thomas

Hi Benoît,

maybe it is too warm at the location of the source? An air infiltration source does not automatically release a certain amount of moisture, it only releases moisture if the temperature at the location of the source is below the dew point temperature of the indoor air. (The model assumes ...

Hi Benoît,

did you make sure that either the stack height or the overpressure parameter of the air infiltration model is non-zero? If both are zero, the moisture source will be zero, too.

Kind regards,
Thomas

Hi bamboo,

the WAC file contains the average hourly radiation intensity in Watt/m². If the average radiation intensity is 1 Watt per square meter, this is the same as 1 Joule per second and per square meter. The total energy input after one hour (3600 seconds) is 3600 Joule per hour and per square ...

Hello bamboo,

WUFI does read rainfall in a KLI file. If in your case it does not, you may have some error in the file format.

However, if you wish to use rain data or solar radiation data for your simulation, there is another reason why you should prefer the WAC format:

Rain and radiation are ...

Hi bamboo,

if your aluminum sheet is at the surface of the building component, its only hygrothermal function will be to prevent the absorption of rain water and the exchange of vapour with the outside air. Due to its small thickness and high thermal conductivity, its effect on the thermal ...