EP, EK and EU – What do these terms mean?

Usable, primary, and final energy – what do these terms mean?

When building a house, you will encounter many specific technical terms, the knowledge of which can be helpful. Abbreviations such as “Ep”, “Ek”, or “Eu” can be difficult to understand for those who have not previously dealt with investments in construction or energy. However, knowing them can facilitate later management of costs related to electricity consumption by the house.

“EU” – The essence of usable energy

Usable energy (abbreviated as “Eu”) is the amount of energy necessary to supply each square meter of a house. It is the most important parameter when calculating the energy costs of a house already at the stage of formulating its construction project.

The energy demand of a building depends on various factors. Among the more important ones are:

• The type and construction of the roof and walls.
• The form of thermal insulation used, including the level of thermal insulation of windows and doors.
• The ventilation model used in the house and the associated level of heat loss.
• The geographical location of the building and the resulting differences in demand, and thus also in energy costs in different cities in the country.
• The positioning of the house in relation to the cardinal directions, i.e., taking into account the maximum possible exposure to sunlight.

A satisfactory value for usable energy should be up to 40 kWh/m2. The lower this indicator, the better, as it relates to lower energy losses needed to heat the building.

“EP” – What is primary energy?

Primary energy (“Ep”) is an indicator of formal importance because it takes into account the need for the entity to adapt to changes in construction law. European and Polish law continually emphasizes the need to reduce energy from non-renewable sources at the expense of promoting energy from renewable sources. Financial support is also provided for initiatives related to adapting energy solutions included in renewable energy sources (OZE). After 2014, the construction law systematically reduced the indicator of a building's energy demand from non-renewable sources. For newly constructed single-family houses, the value of this indicator is currently 95 kWh/m2 per year, but from 2021 it is to be reduced to 70 kWh/m2 per year.

The value of the primary energy indicator means for the investor roughly the necessity to apply energy-efficient technologies when building a house to better comply with environmental and legal requirements. The use of technologies aimed at utilizing renewable energy sources can be useful here.

“EK” – The significance of final energy

This term refers to the energy delivered to the building to ensure the appropriate temperature while considering any losses in the generation and transmission of heat throughout the building. The height of this indicator is mainly influenced by the efficiency of the heat source, e.g., the boiler.

In measuring final energy (“Ek”), it is especially important to consider methods and techniques for reducing energy losses. Two main methods are the best possible thermal insulation of the building to retain warm air inside, as well as designing the interior of the house in an optimally airtight manner, equipped with a mechanical ventilation system with efficient heat recovery.

Only through the above solutions is it possible to ensure efficient air circulation inside the house. Efficient circulation is one that allows effective and uninterrupted air exchange, including the removal of both water vapor and carbon dioxide. This is important for ensuring the safety of individuals and providing them with proper comfort while staying in the house. Mistakes at the ventilation design stage can result in poorer well-being for residents or increase the risk of mold on the walls. Mechanical ventilation with a heat recovery system additionally allows for optimal use of already "used" air. The heat from the latter can be used to warm fresh air inside the entire building.