Natural ventilation for part L

[swilson]

When running part L calcs for a space that is naturally ventilated I normally set the aux vent system to none. This is to ensure no auxiliary energy is used and also to ensure that air exchanges aren't contributing to the heating demand in winter when the windows would all be closed anyway.

Is this a valid way of modelling a room with natural vent.

[Complex Potential]

Hi Wilson

I think that sounds perfectly reasonable but I have to admit that I've never tried it. I've noticed that setting the ventilation type under the system dialogue box to "Natural" does not actually remove the aux vent loss from the room heating load under vista which I've always found annoying.

Perhaps I'll have to try this and see what happens.

[swilson]

thanks complex,


if you do test this let me know if you notice any anomalies

[JohnLloyd]

Unless the Aux Vent system has a heat recovery percentage applied, this will have absolutely no impact on the results.

The aux vent applied by the NCM templates is always set to put the air into the room at external ambient conditions so there will never be a 'ventilation' heating or cooling load in a Part L simulation. You will get an indirect heat loss or heat gain to the room, but this will usually be fairly small as the NCM aux vent is only meant to represent the minimum fresh air requirement for that room, irrespective of whether that fresh air is provided mechanically or naturally.

I believe the associated fan power and whether a room is mechanically or naturally ventilated is dictacted by the main HVAC system setting, rather than the Aux Vent system.

[swilson]

Well it was the heat loss from the room I was most concerned with, I guess in reality I should leave it in to make sure the heating loads are correct, even if the difference is only minor.