"Environmentally sustainable housing" is a broad term describing a range of methods, technologies and practices aimed at reducing the ecological footprint of human settlements. There are two most common approaches in regards of construction material:

construction with natural, locally sourced materials

construction with modern insulation materials 

 These are combined with two main types of buildings in terms of energy flow:

passive buildings, constructed to maximally utilize the energies present in the environment (sun heat, ground heat)

active buildings, integrating devices for harvesting renewable energy sources into the buildings (solar heaters, PVs, wind turbines etc.)

 Although crucial, the environmental sustainability aspect in construction of houses and residential buildings does not solve the main socio-economic problem associated with housing - very high price. Although considered a necessity for any normal human existence, the market price of houses and apartments in Europe is equal to (on average) 20 yearly incomes, making it a life-long issue.

In order for the housing to become sustainable, shouldn't it also be affordable?