2.3. Energy-performance buildings definition

scale level, taking into consideration the whole life-cycle of the buildings, until to their end of life stage.

A circular economy is a concept that is restorative or regenerative by intention and design. It replaces the linear economy and its ‘end of life’ concept with restoration, shifts towards the use of renewable energy, eliminates the use of toxic chemicals and aims for the elimination of waste through the design of materials, products, systems that can be repaired and reused[27].

Several principles of Circular Economy are defined, such as[28]:

1. Eliminate waste, pollution, negative social & environmental impact,

2. Keep products and materials in use as long as possible,

3. Regenerate natural systems.

More on circular economy is presented further in the latter chapters.

As the requirements for the energy-performance of buildings have changed and have been raised throughout the years, several categories of buildings can be met, such as:

 Low-energy houses are buildings with annual heating thermal loads below 80 kWh/m2a.  Three liter building has an annual heating energy consumption of 30 kWh/m2a (or 3 liters of light fuel oil/m2 per year), with an envelope airtightness of n50≤1h–1 (less than 50 airchanges/hour).  Passivhauss are designed by utilizing the potential of passive solar heating and cooling techniques. Their annual energy consumption for heating is less than 15 kWh/m2a with a total consumption of primary energy is less than 120 kWh/m2a, the annual consumption of electricity is ≤18kWh/m2a, and the heat losses are ≤10W/m2 .

The airtightness less than 50 air changes/hour.  Nearly Zero-energy buildings (NZEB) are defined with the European Energy

Performance of Buildings Directive EPBD as a building that has a very high energy performance.  Zero-energy buildings, like NZEBS, are heavily insulated with almost no thermal bridging. They are designed in such a manner that actively and passively exploit the solar energy, reducing the need for conventional heating systems. The need for heating and electrical energy is entirely produced through renewable sources and are not dependent upon the public electrical grid.  Plus-energy house is an energy self-sufficient building whose energy needs are entirely produced through renewable sources but also using technology for storing its produced excess energy.