MacroFlo airflow rates incredibly high

[andreabotti]

Hello,
I am performing an overheating study for future climate scenarios and as such I am testing different measures to be implemented into the design of en extra care scheme.
When assessing natural ventilation strategies I accidentally noticed that Vista reports extremely high values for natural ventilation, up to 500l/s for a single aspect room (which for that room would equal to about 30ACH!!!).

Because this happens more than on a single day, while the wind speed from the climate file in use is within the norm, can you advise on why these figures.
I am carrying on commercial work and not having this under control will invalidate past, present and future analyses.

Thanks,
Andrea

[pran]

This doesn't sound that unusual to me. It's the sort of thing that happens when you have large opening areas.

If you sit in a small room on a windy day, what's going to give you more air changes? Mechanical vent or opening all the windows?

The other thing that might be driving it is temperature differential. If it's cold outside and hot inside, having the windows open will potentially drive a very large air exchange. If your heating system/casual gains are also adding energy into it, this can exacerbate things.

I'd say check when your peak vent is occurring, look at your outputs in detail next to the external & internal temperature graphs. Then from there it might be logical to check your macroflo opening areas and controls, then your system settings for that room.

[Ornella_05]

Hi everybody,

I have the same problem of Andrea.

My space is a room with normal vertical windows, but with a large roof skylight.

I cannot partialize this skylight because it is actually a glass pane which opens all at once.

Is there a way to set a limit for the air exchange, limiting the maximum ACH?

Many thanks,

Ornella