In this tutorial we are going to look at how we define the building systems in the Zebra model. Building systems include the hot water system, the cooling and heating system, and the ventilation system. All of these things have an energy demand. It also potentially includes solar panels on the roof, which generates energy and helps to offset the building’s energy demand.

As well as defining the energy demands of these systems we also need to define the fuels that they use, because this will allow the spreadsheet to calculate the carbon footprint of these systems.

On the left side of the systems sheet we define for each systems the energy demand, or in the case of the PV panels, the energy generation. On the right side we define the fuels that these systems use. This will be used for to determine the operational carbon of the building.

We start with the ventilation system. We've already defined the ventilation fan efficiency in the space conditioning tab, so these values are brought forward from that sheet and summarized here. Likewise for the space heating and cooling system; we have already defined information about the energy demand of those systems so the values are just brought forward.

The hot water system hasn’t previously been addressed. For this we define the amount of litres of hot water we are expecting to use, and some sensible default values are given. We choose from a drop-down the description that most closely matches the hot water heating system we have. Based on these inputs the spreadsheet will calculate an energy demand for the hot water system.

For the PV panels we can define a roof area and the fraction of the roof that we can put PV panels onto. The spreadsheet will then calculate the amount of solar panels you can place in that area and the amount of energy that will be generated by those solar panels.

On the right side of the sheet we have options to set the fuel for the space heating, the space cooling, and the domestic hot water system. We just choose the fuel type from a drop-down, and type in the efficiency of the system.

That is everything we need to do on this sheet for a complexity level of one. If we increase the complexity level there's a lot of additional inputs to this sheet. For each type of building system we have an option to define the auxiliary energy, which is an additional energy demand other than what has already been covered. We can do this for each building system.

For the hot water system we also have options to override the default values for heat losses from distribution and storage. Likewise for the PV panels we have options to define their efficiency and performance. If we know those values we can input them to improve the accuracy of the calculations.

We will also see much more detailed calculations, including charts which summarize the energy consumption, the operational carbon intensity, and the primary energy for each of the main building elements.