You can use a Meter:Custom object to accomplish this. In particular, the EnergyPlus documentation has an example of calculating building-level Infiltration Heat Loss & Heat Gain by summing zone-level output variables:

Meter:Custom,
  Building Infiltration Heat Loss,          !- Name
  Generic,                                  !- Resource Type
  *,                                        !- Key Name 1
  Zone Infiltration Total Heat Loss Energy; !- Output Variable Name 1

Meter:Custom,
  Building Infiltration Heat Gain,          !- Name
  Generic,                                  !- Resource Type
  *,                                        !- Key Name 1
  Zone Infiltration Total Heat Gain Energy; !- Output Variable Name 1

You can then request hourly output for the custom meter.