System sizing calculations

[msb01]

Hello,
I am planning to include system sizing in my simulation tools. The idea is to find out the cooling/heating system size reduction due to a particular energy efficiency measure. I need to provide a general approach. here is what I am thinking:
1. calculate cooling/heating loads for all the zones
2. Add all the loads (heating or cooling) for the whole building.
3. Multiply by a sizing factor (say 1.2) to get system sizing.
5. convert the system size to ton or MMBtuh
6. User $/ton or $/MMBtuh cost to calculate the system cost
I understand that all the zone loads may not be simultaneous, or system size depends on many other factors but I could not think of any simplify approach. I will appreciate any feedback o the approach or any guidance.. Thanks..

 

[Scramode]

What is your insulation like is the room conditioned or uncontioned first floor south facing?

New York Building Technology Group

 

[msb01]

The buildings are air-conditioned. My tool deals with commercial buildings though the residential buildings are also part of it. Buildings can be any size, shape and have option of defining insulation..

 

[ChrisConley]

What does the system sizing factor come from? A 20% over-sizing factor is pretty generous, especially considering you're sizing based on simultaneous zone peak loads; when solar loads tend to peak at different times.

 

[msb01]

ChrisConley,
ASHRAE 90.1 requires sizing of 1.25 for heating and 1.15 for cooling so I was just averaging it out. In general do you think this methodology is correct? Any suggestions will be highly appreciated?

 

[msb01]

Any other comments/suggestions?? Thanks..