Balances not matching in colder climates

[Bonilauri]

Hello,
I'm using WUFI 6.1 and I'm having trouble with analyses in colder climates (northern US, Canada).

In milder climate zones, all works fine.

In colder climate zones, the two balances diverge dramatically. Balance 1 has usually positive values, while Balance 2 has negative values.

The latest calculation I got Balance 1 = 14.43 kg/m2, and Balance 2 = -42.78 kg/m2 (2410 convergence failures).

See attachment for total water content over 3 years calculation.

Thank you!

Enrico

[Christian Bludau]

Hi Enrico,

The reason may be the occurrence of more interstitial condensation in cold climates.
Did you try to use the adaptive time step control in the Control - Numerics settings ??

Christian

[Bonilauri]

Hello Christian,
Thank you! It seems to be working properly now.

Is there any side effect in having the Adaptive Time Step switched on all the time? Would it make the calculation take more time?

Thank you,

Enrico

[Christian Bludau]

Dear Enrico,

to get a feeling for the constructions and behavior, I would recommend to first see, how the calculation runs without ATSC. For example much water in certain places may lead to a slower calculation and convergence problems.
ATSC slows down the calculation only for the time steps, a convergence failure appears, as this time steps are split and calculated each.

Christian

[Bonilauri]

In some cases, the ATSC solves the issue, e.g. with cellulose insulation. In this case, Balance 1 = -1.12 kg/m2, Balance 2 = -1.13 kg/m2, Convergence errors = 0.

If I just replace the type of insulation (cellulose) with Fiber Glass, it does not look so good. Balance 1 = -0.52 kg/m2, Balance 2 = -14.68, Converegence errors = 0.

If I replace it with mineral wool (Roxul Comforbatt), I get: Balance 1 = -0.11 kg/m2, Balance 2 = -23.62 kg/m2, Convergence errors = 0.

I assume that the difference between Balance 1 and 2 in the fiber glass and mineral wool examples above are not acceptable?

All 3 cases above include ATSC, and are calculated for the worst exposure for rain (North).

I ran the same calculations for a different orientation, which also receive considerable rain (South), and I get better results:
- cellulose insulation: Balance 1 = -1.47 kg/m2, Balance 2 = -1.80 kg/m2, Convergence errors = 1.
- fiber glass insulation: Balance 1 = -0.83 kg/m2, Balance 2 = -0.89 kg/m2, Convergence errors = 0.
- mineral wool insulation: Balance 1 = -0.45 kg/m2, Balance 2 = -0.58 kg/m2, Convergence errors = 0.

[Christian Bludau]

Hello Enrico,
no, that balances are to high... Reason may be the moisture storage function of the mineral wool, as the really low functions with the steep increase at the end often lead to convergence problems. For that the moisture content has to reach the rh range higher than 99%, which more happens on the north than on the south side.
Christian

[Bonilauri]

Hello Christian,
Thank you for your support.

When you say that my balances are too high, do you mean that the difference between B1 and B2 is too high, or that their absolute value is too high, and that they should be close to zero?

Thank you!

[Christian Bludau]

Sorry, I was talking about the difference between balance B1 and B2.
Christian

[Bonilauri]

Ok thank you!