Time of Design Peak Load

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I don't know if this has happened to anyone else in their HAP calculations. But I built a project in HAP, and the cooling design peak load is occurring at September (with small loads) when it normally should be occurring in July. I am not sure why the calculations are doing that. Has anyone else run into this problem?

Thanks and Regards,

Kate Mayberry

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Hi Kate,

This isn't very odd, although the typical peak cooling load would occur in July but there are other factors that would affect this such as building rotation, envelope materials, ventilation type, infiltration rate, occupancy schedules (holidays)...etc

The sun path over the Fall faces the side walls of the building more than it would in the Summer when the sun path is more perpendicular to face the roof. For example; if you have a well-insulated roof and walls with bad U-value materials then you should expect a higher heat loss in the Fall due to heat loss by convection = Higher Cooling Load.

This also depend on the location of the project, in some hot areas the climate temperature doesn't differ much in Sept from July.

I hope this help.

Khaled Fouda, LEED GA
Integrated Energy Concepts Engineering, P.C.

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