Fresh Air Amount Considered in Thermal Analysis

[sean.m.hayes]

Hi,

I have a question regarding the HVAC in Ecotect, I wonder if anyone can help please?

I have read the help file on the characteristics of the different types of HVAC systems in Ecotect (Natural Ventilation, Mixed-Mode, Full Air-Conditioning etc.). Does anyone know please how much fresh air Ecotect uses in the Full Air-Conditioning mode? I understand the infiltration rate can be changed to reflect an airtight or leaky building, but is there a way to change the air changes per hour brought about by the HVAC system please? 

I presume the values that are input to the sytems library for SBEM export don't have an impact on this?

Many thanks,

Best Regards,

Sean

[Pennetier1 · Accepted solution]

Hello Sean, 

Ecotect does not really calculate the specifics of any HVAC system, since there are so many out there and it was not the intention of the software to try to predict the energy usage of such system.  Instead, it calculates and predicts thermal loads based on design variables, which would have to be dealt with by any sort of mechanical system.  Thus, under Resource Consumption, we cannot see the energy usage of the cooling or heating as it would be dependent on the efficiency of the system, and its particular fuel.

So to get back to your original question, no, there is no input for the ACH for the Full Air Conditioning system, as it would be very much dependent on a specific HVAC system.  But if that number is known, perhaps the overall building ACH of the zone can be adjusted to reflect that, although I do not know how I would go about it...  I assume it would be a simple addition to the natural infiltration.  With that said, you can also use your local building code to determine what is the minimum ACH (or cfm - you'll have to do some conversion) required per occupant, and you can enter that in the ACH box by using the drop down menu.

And since we are on the subject, keep in mind that the ACH input in Ecotect is what we would call the ACHnat - Natural Infiltration or Natural Air Change Rate, which is different from the widely used ACH50, wich is calculated at the specific pressure differential of 50 Pascals. There is a conversion to go from ACH50 to ACHnat, see this link for reference.

The Wind sensitivity input is yet another variable, along with your model'environment selected under the Project page > Local Terrain or the Location button under the Thermal Analysis tab. 

I hope this helps clarify things a bit.

Cheers,

[sean.m.hayes]

Hi Olivier,

Many thanks for this clarification, much appreciated!

Best Regards,

Sean