In this tutorial we are going to look into the requirement sheet of the zebra model. In this sheet we define our basic design requirements. This includes our environmental philosophy, for instance do we want the building to be zero carbon, and it also includes some basic details of the building we're designing, such as its treated floor area.

In this first section of the requirements sheet we define our energy and carbon philosophy for the building. This is essentially the requirements we expect our building to achieve. In the second section we define some key characteristics for the building.

We start with a space heating demand standard. This is the maximum amount of energy our building is allowed to use for heating. It's expressed per square meter of floor area and per year. The spreadsheet is filled with default values. So the default from passive house is 15kWh/m²(TFA)/a for this.

The space cooling demand is just the same thing, but for cooling. So its the maximum amount of energy we can use to cool the building.

The primary energy standard is the maximum total energy we can use to run the building. This excludes any offset, so if we have PV panels this doesn't go into this. It's a gross energy standard, and it also includes any upstream offsets used to generate the energy. If we're talking about electricity for instance it will include the energy required to extract the fuel, and the energy used to turn that fuel into useful electricity.

The lifetime of the building is needed because we study both embodied carbon and operational carbon, so we need a frame of reference to compare these two to see which is the dominant factor.

The embodied carbon standard is the maximum amount of carbon per square meter of area that we're allowed to use to construct the building. It doesn't currently account for embodied carbon for maintenance of the building, or for demolition of the building. Good practice for this at the moment is 500kgCO₂e/m²(TFA).

Lastly operational carbon is the carbon needed to run the building day to day. This is the amount for instance used to heat the building, offset by any energy we might generate such as from the PV panels on the roof. The aspiration at the moment is for zero carbon buildings, so zero is the default value for this.

In the next section we have the basic building characteristics. At a complexity level of one you just define the treated floor area. The treated floor area is the usable area by humans. It would include the floor area within a room, but it wouldn't include the voids for walls or service ducts for instance. As a rule of thumb if you have a building with stairs the treated floor area is around 90% of the internal floor area, and for a building without stairs it would usually be about 97%.

If we increase the complexity level we'll see some additional inputs below the treated floor area. The first is the thermal mass level, which is the ability of the building to store heat and then release it at another time. In a cold climate for instance this may be useful, because a building may warm up during the day when it's hot, and then it may continue to release that heat at night when it cools down. This can improve the thermal efficiency of a building. Typical values are between 20Wh/K/m²(TFA) for a lightweight building or 100 for heavyweight.

The heating set point is the point at which we would start to heat the building. We would aim for the building to not get cooler than this point, and the default for passive house is 20°C, but you can override that value at higher complexity levels. The cooling set point is just the same but for cooling, so it's the point at which we would start to cool the building down.