Proposed vs. Standard

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I have created an EnergyPro model for a college campus. The model runs and generates a report. However, there is a big difference between the standard design and proposed design for the Space Cooling load which is in kBtu/sqft-yr. The standard is 136.13 kBtu/sqft-yr and proposed is 343.37 kBtu/sqft-yr.  

How should I change my model to reduce the space cooling load? I tried changing the walls U-factor and changing the equipment capacity..but that didnt work. Changing the walls U-factor reduced the cooling load by less than 5 kBtu/sqft-yr.  

 

saman1366's picture
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Changes in load that are that significant usually come down to 1 of 2 things (or both). I don't think it would be the u-factor of the walls because wall conduction load isn't typically 50% of the load in typical buildings.

Here's what I would first consider (in this order):

1) The amount of glass and or glass parameters. Glass can often be 60% or more of the cooling space load.

2) ventilation issue (since it is in the space load, perhaps ventilation is being supplied directly to the space). 

My other thoughts would be that

The different systems are reporting block values (ie proposed is fan coils or something like individual heat pumps), vs peak values (a vav system in the baseline).

Or, I suppose if the proposed system is a VAV system, the design is accounting for reheat in the space cooling load, thus increasing the total cooling load.

Bob F's picture
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The issue was with the EER. I had my AHU EER set to 13. But the "Performance Eff Ratio" in the "Performance at ARI Conditions" section was set to 4. My cooling load went to to 130.13 kBtu/sqft-yr after I changed the 4 to 13. I thought there there was one EER value for an equipment but I was wrong.

Also the heating coils in the vav boxes were driving up my heating load. Your last comment kinda hinted me to check those since my heating was over the standard.

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