"How do I calculate and plan the usage of my building?"
Once you know your site, you have to look closely at what is actually happening inside the building to figure out how it will consume energy. Not all buildings handle heat and air conditioning the same way—it mostly comes down to who or what is inside, and how big the building is:
External-Load Dominated (a.k.a. Skin-Load dominated): If the future building on your land is a dwelling or space that only serves a handful of occupants within a household—like a single-family house, a small apartment, or a condo—then you need to focus on the external load. In these buildings, the climate outside controls everything. The heating and cooling needs change directly with the outdoor weather, temperature swings, wind, and how much sun hits the roof and walls.
Generally speaking, a skin-load dominated building has high surface-area -to-volume ratio. Small, thin, or low-rise). The consumed energy is driven by the envelope performance, such as U-value, insulation R-value, window glazing’s SHGC (solar heat gain coefficient) and the tightness of the envelope (measuring its air infiltration denoted as ACH or CFM).
Internal-Load Dominated: If your proposed building is a facility that serves many users and visitors—like a busy office, a hospital, or a retail store—then you need to calculate the internal load. These buildings generate so much heat from people, bright lights, computers, and equipment that they are require cooling. In fact, deep core spaces in a large office building often need air conditioning even in the middle of winter because of all the internal heat trapped inside!
An internal- load dominated building has low surface-area-to volume ratio. They have larger floor plates, multi-stories and densely occupied. its consumed energy is driven by internal heat gains, such as lighting or equipments.