There are several key things, which should be taken into consideration when defining ZEB:
- units of the balance – cost , primary energy, CO2 units,
- type of energy included in the balance – building operation, energy use related to users (DHW, appliances, lighting) or embodied energy
- requirements – maximum energy use, minimum indoor environment quality , type and
application of RES
- requirements for building-grid interaction – storage capability , effect on peak load , time building can survive disconnected to the grid.
A zero energy building is any type of building with zero net energy consumption and zero carbon emissions. Zero energy houses are autonomous from the energy grid supply.
There are several definitions of what zero energy building means in practice:
- Net zero site energy use building - amount of energy provided by on-site renewable energy sources is equal to the amount of energy used by the building.
- Net zero source energy use building – generates the same amount of energy as is used, including the energy used to transport the energy to the building.
- Net zero energy emissions building – is generally defined as one with zero net energy emissions, also known as a zero carbon building or zero emissions building.
- Net zero cost building – the cost of purchasing energy is balanced by income from sales of electricity to the grid of electricity generated on-site.
- Net off-site zero energy use building – may be considered a ZEB if 100% of the energy it purchases comes from renewable energy sources, even if the energy is generated off the site.
- Off-the-grid building – is stand-alone ZEB that is not connected to an off-site energy utility facility.
A net-zero energy house is one which creates as much energy as it consumes, considered energy self-sufficient through the use of on-site renewable energy, enhanced with energy efficient house technologies.
Energy supply options for ZEB
- Low-energy building technologies – Daylighting, high-efficiency HVAC equipment, natural ventilation, evaporative cooling, etc.
- On-Site Supply Options – PV, solar hot water, and wind located on the building or on-site, low-impact hydro
- Off-Site Supply Options – Biomass, biodiesel, wood pellets, ethanol, utility-based wind, or waste streams from on-site processes that can be used on-site to generate electricity and heat, emissions credits and others.