Agreed. Infiltration Ventilation objects also account for wind and temperature differences to vary the design flow rate. The problem is estimating or calculating the design flow rate.AFN does not require so much guess work, but also has limitations. Large openings and horizontal openings are unsurely modelled (if you read some of the old Contam and AFN papers you will understand why). You'll need to input some crack coeff. data which needs some "guessing", but luckily the errors resulting are small. AFN is the most accurate, but you can get lost in its complexity. For complex models some softwares like Design Builder can automatically generate you the network. But the downside is you will have a crack on every surface. That's often only interisting on the envelope, and the massive size of the network slows computation.
In building practice it is acceptable to estimate calculate a design infiltration rate. If you use two models to compare properties, you will still be comparing apples with apples.
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, YuanLu Li <yli006@...> wrote:
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> Not easy. AFN will give you many details. However, I only look for the zone temperature with ventilation object. Use external shades and internal heat control (vent the heat sources out directly.)
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> The main difference with and without AFN is the exact location of the air flowing in and out of the building and the air flow path. They are dependent on the outside wind condition. If the ACH rate is about the same as with the AFN simulation, the room temperature below 28°C may be considered as comfortable simulated using EPlus with the windows closed and with ventilation object to feed the outside air into the building. Mr. Ooi, KB may be able to add to this. In the actual buiding, the windows and louvers would be open to provide a similar ACH rate or moving air in the room with a fan. Dr. Li
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> From: zqianmin@...
> Date: Thu, 21 Jul 2011 10:40:29 -0700
> Subject: [EnergyPlus_Support] Natural Ventilation
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> Hello, I have question about natural ventilation.
> How to model natural ventilation in energyplus? Do I need to define like window opening schedule or any precalculation? There is no auto control for these window, and what I have are window material, size, and radiant system design. For local condition, dry hot summer temperature, natural ventilation take care of the latent load firstly, even it will increase zone sensible load, and the radiant cooling will take care the sensible load. No mechanical fan at all.
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> I saw the object of AirFlowNetwork, but haven't try it yet. I would appreciate your opinion. Thanks.
> Qianmin
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