Air system input sensible

[kczyze]

I get quite a weird results for 'air system input sensible'. The value doubled after I used constructions with lower U-values. The effect should be opposite I think.. As I understand 'air system input sensible' equals the heating load for the use of system outside air supply, which is constant (from Building Template Manager).
It would be great if you could answer me for this question.
Kinga
PS: I just checked that I only set min flow rate in Building Template Manager, were can I set the max flow rate, because in Apache Systems it's not active.

[KasperS]

I might have misunderstood what you mean, but if you mean the minimum flow as the airchange in the building template manager, then its a constant value, unless you assign it some profile. If you want to work with min/max then you have to use Apache HVAC, where you can set the maximum flow rate.

[kczyze]

Yes, I mean airchanges.
I want to have 1ach in a zone (mechanical ventilation), and I assume no natural ventilation. I want to see what's the energy used for heating this air flow.
As you say it is supposed to be constant so if I imporve the standard of the construction fabircs within the building this value (heating load) should decrease.
I probably do sth wrong but I can't find out what exactly.

It would be great if you could help me.
Kinga

[KasperS]

By increasing the walls performance it shouldn't decrease the energy used to heat the air. The air with the basis mech vent is just (as i understand it) taking air from the outside. If you want to reduce the amount of energy used to heat the air you have to install a heat exchanger that can reuse the heat from the ventilation air. This however can only be modelled in apache HVAC.

[kczyze]

Ok I would agree if this value stays constant, but unfortunatelly it increases! The value doubled after I improved the constructon of the walls, so it is not correct for sure. I have no idea why is that and I really hope somebody knows the answer.
Kinga

[KasperS]

Which results in VISTA are you looking at?

[kczyze]

The problem occurs even if I dont use air-conditioning but only mechanical ventilation (I dont care about overheating) so the air flow should be constant or almost constant. (I see the change of air flow on the chart in Vista, when I choose ventilation). In general I analyse in Vista "air system input sensible". So the problem is that I want to have 1 ach in a zone and see the ventilation heating loads, I dont have any natural ventilation and when I improve the construction the volume flow increase twice and also the heating loads and I don't know why.

Kinga

[KasperS]

I dont really know what could cause that. You should try send your model to Support and see if they can help you. You can export your model by: File > Archive > Current project. Then save that file and send it to them.

[kczyze]

Thank you, I will try to send it to them.