Tag Archives: thermal conductance

xxx M. Miljan, M.-J. Miljan, K. Keskküla (Leiten) and J. Miljan
The combined impact of energy efficiency and embodied energy of external wall over 30 years of life cycle
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The combined impact of energy efficiency and embodied energy of external wall over 30 years of life cycle

M. Miljan, M.-J. Miljan*, K. Keskküla (Leiten) and J. Miljan†

Estonian University of Life Sciences, Institute of Forestry and Rural Engineering, Chair of Rural Building and Water Management, Fr. R. Kreutzwaldi 5, EE51006 Tartu, Estonia
*Correspondence: martti-jaan.miljan@emu.ee

Abstract:

Decreasing the energy consumption in production and building activity is the main aim nowadays as well as in the future. Taking into account that almost 50% of European Union’s final energy consumption is used for heating and cooling, of which 80% is used in buildings it is essential to minimize this amount beforehand. Looking at the energy losses we see that the main heat losses are caused due to the transmission through the envelope and ventilation system.
EU energy efficiency target for buildings to 2030 is at least 32.5%. According to this, national energy efficiency action plans were done, which mean that existing building stock need renovation and new buildings will be constructed according to the energy efficiency requirements. One important factor to improve energy efficiency is to modify thermal transmittance of the envelope. In 2017 minimum energy efficiency requirements were validated in Estonia and determined that the thermal conductance of outer wall must be less than 0.22 W m-2 K-1 (recommended range of U = 0.12–0.22 W m-2 K-1). According to this the energy loss through the envelope was calculated over the year taking degree-days as bases. In our area this number is 4,933 degree days per year, what gives us the calculated heat loss through the envelope 10.22 kWh m-2 if the thermal conductance of the wall is 0.092 W m-2 K-1. This required value of thermal conductance we can achieve using good insulation materials. Still there are possibilities to choose between insulations.
Done tests and calculations allow to conclude that energy consumption during building life cycle together with embodied energy of building materials gives us more realistic overview of the energy efficiency of the building. Our results confirm that the use of local natural insulation materials is 1.67 times more sustainable and energy saving than using industrial materials.

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