All classes except class A may apply to individual or multiple buildings.
1.1.3 EUIEnergy use intensity is a vital and useful measure for designing NZEBs. EUI is the total annual energy use of the building divided by gross floor area. It is an absolute measure of the building’s energy performance and a mean to compare it to other buildings or to fixed baselines. However, the relative comparison based on EUI is most useful when comparing buildings of the same type and in similar climates.
1.1.4 Active and passive design Passive design is providing heating, cooling, ventilation and lighting by using architecture to harvest free energy from the environment.Development of passive design strategies involves climate and site assessment among other factors, to identify the opportunities for passive strategies. Then the building’s performance requirements; thermal comfort, ventilation and required levels of lighting must be analyzed. The passive system must be designed to meet these requirements A passive system does not need any active systems to satisfy the needs of occupants. However, due to the dynamic nature of free energy passive systems cannot be relied on completely and thus active systems are used to complement passive systems or to function when passive systems are not accessible.
Active systems are mainly mechanical systems designed, just like passive systems, to meet performance requirements. They utilize energy-efficient options and sophisticated controls. In a successful case of NZEB passive and active systems are inseparable; the two systems should be integrated leading to a hybrid design.In a hybrid design, the passive strategies reduce energy required from active systems by harnessing the free energy of the environment, while the active strategies supplement the passive system when needed. The resulting reduced energy use in an integrated design makes it possible to use more efficient active systems. 1.
1.5 Energy efficient system The process of designing energy efficient active systems starts with deciding how the building uses energy in order to achieve an integrated design and reach net zero energy. Also, establishment of energy consumption sets the renewable energy generation requirement and the energy efficient active system must be integrated with the on-site renewable energy technologies. The energy used by the active systems is referred to as regulated energy and includes energy used by HVAC, hot water system and lighting.
The remaining energy use is referred to as plug load energy.Selecting which type of system to utilize for each component of the active system must be based on both energy efficiency and cost-effectiveness. 1.1.5.1 Heating, ventilation and air conditioning (HVAC)The purpose of HVAC systems is to provide satisfactory air quality and comfort in the space. The levels of air quality and comfort are not generic but rather subjective depending on preference and norms and thus should be selected in the NZEB design stage based on the specifics of the building.
Different HVAC systems have different applications depending on climate, site, building size and building type. HVAC systems can be single zone or multi zone systems. Zone refer to a space heated or cooled controlled by one thermostat, the space can be a room or the whole building. Multi zone systems are applicable where there are a range of spaces with different heating and cooling requirements.Furthermore, there are ducted and ductless systems, in the later indoor units is installed in each space for individual heating or cooling while in ducted system cooling air heating air is provided to each space from one central location through ducts.In addition, HVAC systems can be variable air volume systems (VAV) or constant air volume systems (CAV). In VAV systems the supply air temperature is constant while the volumetric flow rate varies. By changing the amount of air supplied to each space, the system controls the temperatures within the building.
On the contrary, CAV systems supply air at a constant volumetric flow rate but different temperatures. 1.1.5.2 Hot water system In residential buildings a significant percentage of energy use is for domestic hot water (DWH). In a NZEB, utilizing solar energy and using a solar thermal energy system for generating DHW is a conspicuous approach.
