Zero- energy building in California:
Today issues like global warming, air pollution, decreasing energy sources like fossil fuels and etc cause to build Zero-energy buildings. According to Afshari basir (2012) Zero-energy buildings have different definition in countries such as USA, Canada and England that these kind of buildings are constructed. He claims that one of the definitions is to make the on site production of energy and consumption equal. Another definition of Zero-energy building is to reduce the amount of carbon emission and also to reduce the total cost of using energy. I watch a video on you tube about a zero-energy house in California. This modern house consisted of  6 modules that were made in a factory in 3 months. Assembling of building took just one day. After that a few days were spent to complete the details. Despite the speed of construction,the building have solar panels, hydronic heating and the passive solar design that help reduce electric consumption noticeably. The total cost of the building not including the land become 500,000 American dollars that is not seems to be efficient. Although after years the owner will make profit of not to paying for energy in my opinion the construction cost of these buildings should be cheaper to attract more people to build zero-energy buildings in the first place.

source: https://www.youtube.com/watch?v=VQ-70PnDKno
 Afshari basir,M 2012,Zero Energy Building,Mechanical and Aerospace Engineering, pp 2075-2080.