Natural ventilation and external openings operation

Franck.Boutte · Posts: 13

Hi,

I'm trying to model a natural ventilation , and I have some problems too.

I don't know the ach. I want to estimate the % of openings and the timing for in order to maintain a good temperature in summer (cooling design mode).

I check ventialtion as calculated in model options, in order to have ventilation calculated with wind pressures, buoyancy, and openings operation.

But, when I change the parameter for openings operation from 0% to 100% (with natural ventilation ach unchecked in HVAC tab), nor the external nor the external natural ventilation change.

I do not understand the results. What could be the problem ?

Thanks

Franck

Andy Tindale · Posts: 1205 Location: Stroud

Hi Franck,

It's hard to be sure why you are getting no natural ventilation in your model but here is some information which hopefully will help to find out:

When the natural ventilation mode is 'Calculated', natural ventilation and infiltration heat loss/gain output data are displayed combined under 'External air' instead of 'External natural vent.' and 'Infiltration' data as it is on the Cooling design results screen.

One possible reason for getting zero 'External air' with calculated natural ventilation is that natural ventilation operation could be switched off on the operation schedule. This could be because the simulation period is in a holiday period and HVAC operation has been set to coincide with activity operation ('HVAC + natural ventilation operates with occupancy' building model option).

Also, if you are looking on the Cooling design tab and have Natural ventilation switched off on the HVAC tab then you will get no External natural vent. This is because calculated natural ventilation is not allowed in heating and cooling design simulations (scheduled natural ventilation data from the HVAC tab is used instead).

If this information doesn't help you to solve the problem, please post the model on the forum (see 'Add an Attachment' when you post a reply). Otherwise send it by e-mail to the support desk.

Best regards
Andy

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