**4.1 Uncertain parameters**

ZEB is generalized as a type of sensitive building since its target is affected not only by the variation of building energy load but also by the fluctuation of local renewable energy resources. In general, a comprehensive sensitivity analysis is required to be conducted by considering both on-site generation and building energy load, as shown in **Figure 10**.

In terms of on-site RES generation, the availability of renewable resources (e.g., solar radiation and/or wind speed) and RES parameters (e.g., PV/WT efficiency and life time) can directly affect on-site energy generation for building electricity supply and thus greatly affect RES selection as well as the corresponding building performance.

#### **Figure 10.**

*Four aspects in terms of sensitivity analysis for ZEB.*

In terms of building energy load, building design parameters (e.g., indoor set temperature and humidity, thermal insulation of external walls, window area, etc.), operational parameters (e.g., outdoor temperature and humidity, solar radiation, etc.), and energy system efficiency (e.g., lighting efficiency, HVAC efficiency, etc.) are the main parameters affecting building load.

Economic parameters including the price of RES, feed-in tariff, and electricity price from/to the grid are also key parameters affecting RES selection and ZEB performance. In addition, many researches have found that both the building energy load and the local renewable resources are different even for the same building located in different climate zones, which indicate that different key design parameters may exist for different climate zones and should be further identified.
