The idea of a net Zero Energy Building (nZEB) is greatly discussed in Finland. By definition, the nZEB has zero net energy consumption which is based on the balance of energy produced and consumed in a building and usage of renewable sources. The nZEB concept is of great interest in the EU as the EBPD Directive requires that newly constructed housing must be net zero energy buildings from 2020.
Currently in Finland, there is great interest in building low-energy houses that are air-tight and have mechanical ventilation system with heat recovery. Emphasis today is placed on achieving the overall energy consumption of 150 kWh/(m^2.a) which includes heating consumption of approximately 40-60 kWh/(m^2.a), which are certainly low figures for the region, but there is still a lot to do. Today’s average airtightness in low-energy buildings is below 2.0 h^-1 at 50 Pa, although the current Finnish Building Regulations 2011 requires n50 = 4 h^-1. The gross heated area for residential housing is around 160-200 m^2 accommodating a family with 4 up to 6 children. The most common building types are brick, timber and concrete structures along with log houses with log thickness of 200-270 mm providing very air-tight envelope (on average below n50 = 2 h^-1). The energy retrofitting for buildings with life span expectancy of 100-300 years is ongoing work that uses a special approach with energy savings cards describing saving potentials separately.
Achievement of nZEB is based on the idea that the passive house concept should be used as a baseline for building a house and additional renewable on-site resources would supply the necessary energy and any energy surplus would be send to district grid system. Finns want to use their own alternative passive house concept based on the Finnish climatic conditions with achievable values of 20-30 kWh/(Br m^2.a) for the gross heated area. The house will have an intelligent control system linking all building services to provide the good indoor climate. Such super-insulated air-tight buildings will still have challenges to adapt to the Finnish lifestyle based on daily use of wood-based saunas and preferably open fireplaces creating potential problems with smoke spreading throughout the whole house.Image: nZEB by http://nzen.info