Modeling of Floor Constructions in WUFI

[Iain McIver]

Hi Everyone,

Im trying to find out whether I can model a floor construction in WUFI ?.

Can I just set the orientation of my assembly to 0 degrees (like a flat roof) and then use an external climate file as my internal climate and vice versa. In effect modeling like a flat roof except with the external climate below rather than above??

Is there a different way of modeling floors??

Any advice would be much appreciated.

Thanks
Iain

[Christian Bludau]

Hello Iain,

For modeling floors there are the following possibilities:

Floor with soil:
Left side is soil, right side is indoor conditions

Floor between stories:
Both sides have indoor conditions. Just assign indoor conditions to the left side as well. You will get a warning, but that will work.

The orientation and inclination is only needed, if you use climate elements like solar radiation, wind, rain... For indoor conditions the temperature and RH are sufficient...

Christian

[Iain McIver]

Thanks Christian,

The floor I am trying to model is a suspended timber framed floor with external air underneath. Is there way to model this type of floor in WUFI?

Also if I did want to model a slab on soil, for the left side climate should I just use the user defined sine curves to show the temperature and RH in the soil?

Thanks
Iain

[Christian Bludau]

Hello Iain,

for you timber floor model the indoor site on the right, the outdoor site on the left. For the outdoor climate you can use a exterior climate file, calculate without radiation (leave absorption and emission empty) and switch of the rain (adhering fraction of rain is zero). Then you have only the influence of the air. You also could use a sine curve or if you know about the conditions, use them.

For the soil i usually use sine curves for temperature with a constant RH of 99 or 100%. If you want to take in account the interaction between soil and slab, you have model a soil layer as well. For that you have to generate a new material and assume some reasonable values.

BTW, the climate file Holzkirchen TRY (Germany) contains measured values for soil in 0,5 and 1m below surface. (Select that file and click on Details...)

Christian

[james bertram]

Good morning

I have read Christian's comments below and would like to check that I am modelling a first floor suspended concrete slab in an office building correctly (ground = unenclosed car parking, storeys above = office space).

I am use three stages:

1) Pour to 3 month - to allow for some construction moisture drying etc. Left side = outdoor climate, right side = 24 hour running average of outdoor to allow for conditions at the underside of the slab.

2) 3 to 24 months - additional floors constructed above . Left and right climates = 24 running average to allow for conditions as above, take initial conditions for concrete moisture from (1) above.

3) 24+ months - operating building. Left side now becomes indoor conditioned, right side remain outdoor (24 hour average as above), take initial conditions for concrete moisture from (2) + add insulation to underside of concrete.

Q: In the above the "indoor" and "outdoor" switch side. I have presumed this is not an issue because climate data is restricted to Temp and RH. But I am not sure on the correct "Surface transfer coeff" settings?

Thank you

[james bertram]

...opps forgot to tick the "notify me" box...

[Christian Bludau]

Hi James,
for the connection to the soil I would use an heat transfer coefficient of 1e9 W/m²K, as there is no resistance. Other settings like radiation or rain should all be set to zero, as they do not appear in the soil. Indoor you can the 8 W/m²K as known.
Greetings,
Christian

[james bertram]

G'day Christian - apologies for the confusion, the suspended concrete slab has an open carpark below and an office above - it is not connected to the ground.

Thanks, James

[Christian Bludau]

If the car park is open to the sides, you can use the outdoor conditions without radiation. As heat transfer coefficient I would suggest a value between indoor (8 W/m²K) and outdoor (17 W/m²K), depending on the ventilation.
Christian

[james bertram]

Thank you Christian