How to determine the energy efficiency class

building energy efficiency class How to determine the ''energy efficiency class of a building'' for obtaining an energy performance certificate and why.

The definition of energy efficiency class is an assessment of the quality of construction. You can compare this to your car's fuel consumption data. Knowledge about home energy consumption can help estimate the economic value of a building and know the cost of maintaining it.

In total, there are seven energy efficiency classes from A to G.

According to the European experience in Ukraine the following gradation of existing buildings has been adopted:

- old buildings, which were built before 2007 and consume heating and cooling up to 300 kWh / m2; (such buildings have priority for energy modernization)

- new buildings constructed by 2016 with consumption of about 150 kWh / m2;

- energy efficient buildings with low energy consumption, about 60 kWh / m2;

- passive houses built according to the passive house standard, with consumption of less than - 15 kWh / m2 per year;

- buildings with zero energy consumption (in fact, these are passive buildings with equipment for energy production to compensate for their energy losses) they consume - 0 kWh / m2;

- Energy + buildings that produce far more energy than they consume.

The minimum mandatory requirements for the energy efficiency class are related to the purpose of the buildings (residential buildings, public buildings in the areas of study, sports, retail, medical, etc.), the surface of the buildings and the location according to the first or second climatic zone.

A mandatory energy efficiency assessment has been introduced for all new buildings.

The first stage in the design phase of a building project is the energy efficiency section of the design documentation, with the definition of parameters for certification.

The second stage is mandatory energy certification before commissioning,

The second stage is carried out by a certified energy auditor who registers the developed energy certificate in the State Energy Efficiency and only after that the building can be put into operation.

The energy consumption of homes is determined in two ways:

1) With the help of calculations;

2) According to actual energy consumption, which is determined by indicators of meters or other metering devices.

The first valuation method is accepted for buildings that have just been constructed or reconstructed. Also to those in which major repairs are carried out. These calculations are made on the basis of architectural drawings, decisions made on the engineering networks and units and details. That is on the basis of the project.

For buildings that already have an estimate of energy consumption for conducting an energy audit with the collection of these meters for a certain period. Usually in a few years. But the availability of project documentation makes it possible to use the calculation method. In practice, the two methods are combined depending on the specific situation. These design data are collected and surveys are conducted. After all, the auditor is reputationally responsible for conducting the surveys.

Determining actual energy consumption only according to meters can have significant errors, for example when the building has not received heat or the operating conditions have been disturbed. This can lead to major errors in determining the energy class.

With the DSTU update and approximation of assessment practices to European standards, not only heating data but also modeling of energy consumption for cooling, ventilation, lighting and hot water supply are being evaluated when defining a building class.

There are three basic methods for estimating energy consumption:

1) Monthly or seasonally;

2) Hourly simplified;

3) Detailed modeling;

When developing an energy certificate, use the first method.

When evaluating a building, it should be considered as a single energy system consisting of an outer shell that is under certain climatic conditions and complex engineering subsystems that work to maintain the specified sanitary and hygienic parameters.

There is the following scheme for calculating energy efficiency:

- Determination of heated and unheated areas of the building, and division into areas that are necessary for the calculation;

- Determination of the parameters of the use of the building, the work of engineering networks, sanitary and hygienic norms and the parameters of the enclosure structures for each selected area;

- Calculation of heat losses due to ventilation and infiltration losses of heat for each month of the year;

- Calculation of internal heat inputs from people, appliances and solar thermal inputs for each zone and month of the year;

- Calculation of energy consumption for heating, hot water supply, cooling and ventilation;

- Calculation of energy and heat losses for the use of energy distribution and storage systems;

- Calculation of energy consumption of total energy consumption for cooling, heating, ventilation and DHW for each month of the year;

- Obtaining total energy consumption for the year;

- Preparation of a report on the assessment of energy consumption for a building.

I would like to point out that the main requirement in the design of houses is to achieve an energy efficiency class not lower than '' C '' (for new buildings), which corresponds to the norm of heat losses through external enclosing structures and engineering networks. But indices of resistance of heat transfer of separate elements are not considered separately from each other. In practice, this means that the annual energy demand of the building takes precedence before evaluating the energy efficiency of the outer shell.

Regulatory maximum specific energy demand for residential and public buildings

Classification of buildings by energy efficiency

Subject to the minimum energy performance requirements of a building not lower than C or not more than 110 kWh / m2, it is possible to use individual building elements with reduced heat transfer resistance values (75% of Rqmin) for opaque parts of exterior enclosures and up to 80% of Rqmin for other structures (mandatory sanitary requirements).

At present, energy classification of homes has been actively started in Ukraine, and all new buildings and buildings that are being reconstructed or overhauled must have an energy certificate before submitting documentation at the commissioning stage.

The building's energy efficiency certificate has been replaced by an energy efficiency passport and is a separate document in the design estimate for the facility.

Obtaining an energy certificate is required for homes with an area of more than 500 m2 when changing their property rights or alienation, for communal or state-owned buildings. Actual energy efficiency indicators must meet the minimum requirements specified in the DBN.

Also, in the energy certificate, we must state how the energy efficiency of the building can be improved. The certificate is valid for 10 years.

In the future, this information, in addition to the database of the State Energy Efficiency Fund, will be included in the cadastre system. Access to the database will be provided on government sites. This will increase the return on energy conservation measures as the liquidity of energy-saving homes will be much higher.