OpenStudio has the concept of Space that doesn't exist in EnergyPlus. The idea is to simplify your life when it comes to inputing people, equipment, etc. Indeed, several spaces can be in one thermal zone, allowing you to bundle for example a corridor and a mechanical closet together, while still inputing logical values for each individual space.
The concept of Space would be kind of meaningless if it wasn't for the concept of SpaceType and the general concept of inheritance that OpenStudio has. The Model Overview while slightly outdated is still very relevant (in fact, the only really outdated thing is that it lists version 0.6.0, the rest holds true).
In practical terms, how is that making your life easier? Let's say you have a theoretical one floor building with 8 apartments (2 people in each), 2 corridors, and one mechanical closet. You want to end up with only 4 zones for the apartments, 1 corridor zone, and 1 zone that bundles the other corridor and a mechanical closet.
- You define 2
SpaceTypes: one for "Corridor", the other for "Apartment". You assign loads: people, lights, equipment to these space types. Some loads you will assign as a function of the floor area, but for apartments you put "2 people" - You create your 8 apartment
Spaces, 2 corridors spaces, and your mechanical closet. - You assign the Apartment and Corridor
SpaceTypes to the 8 apartment spaces and 2 corridor spaces. These spaces will inherit the loads of the space types. You only had to define them at the SpaceType level (this is very similar to the ZoneList here) - You directly assign some loads to the mechanical closet (you could have created a space type for this, but that's not necessary here)
- You then create
thermalZones, and assign them to the Spaces. You will create for example one thermal zone that has two spaces: the corridor and the mechanical closet.
Once you run the simulation, OpenStudio forwards translate to the E+ IDF file, and computes all the right loads for your Zone (remember that the concept of "Space" doesn't exist in E+, only Zones). For the OS:ThermalZone you defined for the mechanical closet + corridor, to compute the lighting power for this zone it will for example do something like: corridor_W/ft^2 * corridor_area_ft^2 + mech_W/ft^2 * mech_area_ft^2.
Overall, this allows you to define loads in one place only (like ZoneList does), but also allows you to aggregate different Spaces into the same Zone, which is not doable out of the box with E+.
