I am doing an ASHRAE 90.1-2007 PRM analysis. We have a DOAS CV laboratory design that has a requirement between 10-20ACH in lab zones and a room set point of 20degC.
The baseline system is System 5 – Packaged VAV with Reheat
Section G184.108.40.206 states airflow rates shall be sized off supply-air-to-room-air difference of 11degC, or the required ventilation air/makeup air, whichever is greater. In our case the required ventilation rate is greater than the flow rate using an 11degC temperature difference (supplying at 9degC).
Design outdoor air requirement =12,400l/s
Supply flow rate at 11degC temperature difference = 7,500l/s
My question is, for the baseline building do we still supply our outdoor 12,400l/s air at 9degC + 2.3degC supply reset (G220.127.116.11) from the AHU? Doing this leads to the baseline overcooling to 11.3degC (9+2.3) and then re-heating to 17-18degC to achieve the space set-point of 20degC. This creates an inefficient baseline and therefore a positive effect for the energy cost saving.
The same problem seems to have been posted here, with the answer suggesting that this is acceptable to overcool and then reheat:
Any help would be much appreciated.