Note that the LS loads report shows the heating load of the zone, this is different than the energy consumed to provide heating by the system. A zone that has no heating load in LS-A still consumes reheat energy if the VAV system is supplying more air than is required for cooling. Or the zone will be too cold.

1) Check the SS-O reports and the unmet hours tabulation for your zones to make sure that the two cases are meeting the temperature requirements.

2) Have you set the minimum airflow requirements for the zones, if these aren't zero minimum spaces? Reheat energy will be underreported if you allow the VAV to modulate lower than the design's minimum for the zone.

The chilled beam case may have less reheat than the VAV system since the configuration allows for less air to be cooled, and then heated up in the non-critical zones. The amount of heat gain required to the zone to satisfy LS-A will still be the same in both cases, even though the systems use more or less energy to deliver that heat to the zone in usable form.

Your other point is correct, internal loads are dissipated at heat, which would offset your need for reheat...your observation is on target that if your modeled internal loads are too high, the heating will be underestimated. (And electricity use overestimated.)

David

David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP
Grumman/Butkus Associates