Dear all,
my building is a warehouse with 3 office areas that, for now, have no hvac system. However, since they are considered a conditioned space, I have to model a hvac system, the same as baseline case. I am trying to model the use of system 4 (packaged rooftop heat pump) in my baseline using Design Builder and autosizing airflow, heating and cooling capacities. However, when using the same airflow, heating and cooling capacities in my proposed design, I get 450 hours of discomfort. I have tried to increase the oversizing of heating and cooling capacities in baseline and using the results in proposed case, but it is still getting difficult to decrease the "Time Setpoint Not Met During Occupied Heating". Does anyone have any idea of what I should try? I am also now questioning if it is necessary to use the same capacities of the equipment and airflow in both baseline and proposed cases.
Thank you in advance!
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5915 thumbs up
July 23, 2014 - 10:19 am
Will these spaces have HVAC in the future? If they have no HVAC then they are unconditioned space.
You do not have to use the same airflow and capacities in the Proposed as in the Baseline. Auto-size them in the Proposed as well including the over-sizing factors.
Isabel Santos
ECOCHOICE SA2 thumbs up
July 23, 2014 - 10:54 am
Marcus, thank you for you help! I was really interpreting this in a wrong way... It is expected that these spaces have hvac, but since there will be 2 different tenants, the building company chose in this case not to select the equipment in this stage. I am going to autosize now proposed case also.
Thank you, best regards!
Isabel Santos
ECOCHOICE SA2 thumbs up
July 24, 2014 - 4:46 am
Marcus,
I am now having another question. Does the Propose case system need to comply with the fan power in G3.1.2.9?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5915 thumbs up
July 24, 2014 - 10:16 am
Yes you do the fan power calculations for the Proposed as well. Essentially you include the Baseline system in the Proposed if there has not been a system designed for that space. It is applied to the Proposed the same way (i.e. using the same methods) as the Baseline, which does not necessarily produce the exact same result (supply airflow, fan power, capacities, etc.). Outside air is the exception as this should be identical.
Isabel Santos
ECOCHOICE SA2 thumbs up
July 24, 2014 - 2:50 pm
Thanks Marcus!