Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
From the T24 2013 NonRes ACM Ref. Manual
2.6.2 Sizing Equipment in the Standard Design
For cooling capacity sizing, compliance software shall use the **OnDay schedule from Appendix 5.4B for occupant, lighting and equipment schedules, respectively. For heating capacity sizing, compliance software shall use the OffDay schedule from Appendix 5.4B for occupant, lighting and equipment schedules, respectively.
I haven't used CBECC-Com, but based on your description it sounds like what you are seeing is hourly results from the design days (several days per year). For winter (heating) design days it is common practice to assume that all of the internal loads are turned off (always 0) because this represents a worst-case scenario where they don't contribute heat and the heating system needs more capacity. On the flip side, for summer (cooling) design days it is common practice to assume that all of the internal loads are turned on (either following the normal schedule or always 1), which will increase the amount of cooling capacity needed. Based on the reference above and your description, it appears that CBECC-Com follows this practice.
