Problem with calculated natural ventilation

koen25071979 · Posts: 28

Hello,

I am having a problem with the calculated natural ventilation in a double facade.
I am using vents in the double facade which are open in summer and closed in winter according to the operation schedule.
When i make an hourly simulation the "Mech Vent + Nat Vent + Infiltration" is high in summer in the double facade, which is normal.
But, also high in winter, not normal.

In designbuilder you note about calculated natural ventilation:

Natural ventilation cooling setpoint temperature
The natural ventilation cooling setpoint temperature controls the activation of natural ventilation. If the inside air temperature is greater than this setpoint temperature (and the natural ventilation operation schedule is on) then natural ventilation can take place. The way this works depends on the Natural ventilation model option.

Note that when using the Calculated natural ventilation model option windows and vents are only opened when:
The inside air temperature is above this cooling setpoint temperature, and

The inside air temperature is greater than the outside air temperature, and

The operation schedule allows ventilation. ????????????????

Because its always warmer in the double facade then the outside temperature, the vents are always open.
So the vents function according to the temperature, and don't function according to the operation shedule.

Is it possible to let the vents work according to the operation shedule as main priority, and then according to the temperature?

In this way i would be sure that the vents are closed in winter and working in summer according to the temperature.

Kind regards

Koen Gyselinck

AOG · Posts: 79

Koen,

As far as I know, schedules have priority over set point temperatures. It means that if you have a schedule in which vents are off during winter period, ventilation doesn’t take place, even if inside air temperature is above set point temperature and outside air temperature.

Just a question: ¿Are you using the correct schedule? I recommend using a compact schedule like this one:

SCHEDULE:COMPACT,
Summer vent,
Fraction,
Through: 31 Mar,
For: AllDays,
Until: 24:00, 0,
Through: 30 Sep,
For: AllDays,
Until: 24:00, 1,
Through: 31 Dec,
For: AllDays,
Until: 24:00, 0;

I hope it helps.

Best regards,

Arturo

Andy Tindale · Posts: 1115 Location: Stroud

Koen,

Arturo is right in saying that schedules override setpoint temperatures. Natural ventilation cannot occur for a zone when the Natural ventilation schedule has a zero value.

Andy

koen25071979 · Posts: 28

Andy and Arturo,

Thank you for your reply, i changed the schedule.
But the results are the same.

Andy, could you take a look into my dsb-file.
I have send it to your E-mail last friday.
I am propably doing something wrong.

Regards

Koen Gyselinck

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