doors and external air

lvidal · Posts: 69 Location: Paris

Hi,

I'm trying to evaluate impact of large door openings on external air entrance.

This is the context :
- I'm using simulation on a winter week.
- The building is a simple one volume shed with four doors.
- Model options : Ventilation set to Calculated
- Airtightness : Model infiltration off
- Last DB version used (1.2.0.022)

I tried two simulations with external doors operations
very different :
A) % area door opens : 100%
% time door is opened : 90%
B) % area door opens : 1%
% time door is opened : 1%

But the results (external air losses) are the same.

My questions are :
1) Do I miss an option in a tab to activate calculation ?
2) Is it possible to simulate natural air flow with the simulation tab or is it only available with heating desing ?
3) How and when COMIS is used ? I mean what options
(general or in edit tabs) allow its use.

Thank's a lot
Laurent

Steve Potter · Posts: 274 Location: newcastle

Hi Laurent

I tried to reproduce the problem that you describe and it looks as if the operational data for doors is being ignored. This part of the DesignBuilder code is maintained by Andy and unfortunately he's away on holiday until the 10th, however as soon as he's back we'll take a further look at this and get back to you.

Regards

Steve

Andy Tindale · Posts: 1115 Location: Stroud

Hi Laurant,

1. You should be able to model doors in the way you had been expecting, but I wonder if you were perhaps working with 'internal doors' operational data instead of 'external doors'? This is a fairly common mistake. Please check that you have the correct data at surface level by navigating to the surfaces with doors.

2. Yes you can simulate natural air flow using the Simulation tab - in fact this is the only tab which will give you calculated natural ventilation. The Heating and Cooling Design tabs always give you the scheduled natural ventilation even if you have selected 'Calculated' ventilation on the model options dialog.

3. Actually, COMIS is not used at all anymore - calculated natural ventilation is now handled by a new airflow solver called AIRNET which has some really good advantages, including solutions at the HVAC time step which give much more stable results.

I hope this helps.

Regards
Andy

lvidal · Posts: 69 Location: Paris

Andy,

Yes, I was working with external doors.
But I've tried again checking parameters at wall level.

I have still the problem.
I upload you my dsb file for I may have forget some option somewhere.

Cordialement,
Laurent

Andy Tindale · Posts: 1115 Location: Stroud

Laurent,

You are not seeing natural ventilation in your model because 'Natural ventilation On' is not checked on the HVAC tab. So, all natural ventilation due to openable windows, doors and vents is excluded from the analysis. You should get the expected behaviour when you switch natural ventilation on.

We will make a change to the interface and to the documentation to clarify that this is required.

Regards,

Andy

lvidal · Posts: 69 Location: Paris

Great ! It works.

May I suggest you to remove the indication 'heating/cooling design only' in the the natural ventilation tab title.

If I well understand, it's the air rate which is only used in design.

Thank you for your patience, Andy.

Laurent

Andy Tindale · Posts: 1115 Location: Stroud

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