Friday 26 February 2021  

Low-energy house

With Energy Efficiency Regulations specifying stringent minimum conditions for the energy performance of buildings, Greece is called to join the leading European countries in regards to the energy efficiency of its buildings.

Complying with Regulations on design and construction methodology and by issuing Energy Performance Certificates, built structures are rated, depending on their thermal balance, in different energy classes (A1, A2, B1, B2, C, D….).  By using ENERGENIUS  software, designers can calculate the energy class of a residential or other building type.

Heat balance  = Heat losses – Heat gains

Low-energy buildings

The construction of low-energy houses (LEH) requires highly efficient thermal protection against heat losses in winter, as well as against overheating in the summer. Thermal insulation must be applied on the entire building envelope in a continuous layer, without any thermal bridges.

Rating of buildings according to energy use for heating is given in the  Energy Performance Certificate Regulations:

In the calculated Energy Performance Certificate a building is rated in an energy efficient class according to the annual energy need for heating per useful floor area of the building  -  Q(NH)/A(u) (kWh/m2a) as follows:

class A1: from 0 to 10 kWh/m2a inclusive

class A2: above 10 to 15 kWh/m2a inclusive

class B1: above 15 to 25 kWh/m2a

class B2: above 25 to 35 kWh/m2a

class C: above 35 to 60 kWh/m2a

class D: above 60 to105 kWh/m2a

class E: above 105 to150 kWh/m2a

class F: above 150 to 210 kWh/m2a

 class G: above 210 to 300 and more kWh/m2a inclusive.

Class A (A1 and A2) – “Nearly zero-energy house”

Buildings known as “passive houses” until today, are being rated under the term “nearly zero-energy house” (~0 EH)” according to the current European legislation.  “~0 energy house” is a low-energy building with optimum energy savings, which does not require a conventional heating system.  When designing a “~0 energy house”, with energy use for heating limited to 15kWh/m2a, regulation guidelines should be implemented with precision, taking into account the location, orientation and shape of the structure, as well as shading, air-tightness, recuperation of exhaust air, etc.  Low-energy houses require thicker thermal insulation.  This has to be installed in a continuous layer on the entire building envelope.  At foundations' level, thermal bridging is minimised by carefully insulating the underside of the foundation slab.   

The successful design of low-energy structures, especially of “~0 energy houses”, requires thorough knowledge of energy-efficient design, compliance with current regulations and effective application techniques.  The education of designers and installers in energy-efficient design is further developed by FIBRAN with the distribution, instruction seminars and use of ENERGENIUS software.

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