EPCs as a tool to improve energy efficiency
According to EU data, 40% of energy consumption in Europe and 36% of greenhouse gas emissions come from buildings; so decarbonisation of the European building stock by improving energy efficiency is a crucial matter. Considering that energy retrofitting usually involves a major renovation of buildings and systems, the energy performance requirements to be achieved must be established within the strategies and incentive programs of public administrations.
Economic and/or financial incentives to address energy efficiency of buildings are linked to energy savings and the improvement of overall efficiency. This is evaluated by comparing the energy rating obtained before and after the energy retrofitting. To set a direct link between the improvement of energy efficiency and access to different levels of incentives, quality data are needed. These data will come from the databases of Energy Performance Certificates (EPCs) that are being developed and managed by the countries or, as in the case of Spain, by the Regional Authorities.
It is important to improve the energy certification process, from issuance to management by the administrations, as it will contribute to reach the goals set on energy efficiency of buildings. At building level, the EPCs report on the building’s energy efficiency, the percentage of renewable energy as well as costs’ information. At district level, city, regional or even national level, EPCs can be used to identify the buildings energy performance, and thusdetect the least efficient buildings. As indicated in RD 390/2021 (Spanish law), the recommendations provided at the end of the energy efficiency performance certificates should contain an estimate of the investment recovery period and also information on its cost-effectiveness.
Subsequent European Directives on energy efficiency and on energy efficiency of buildings establish requirements for EPCs in case of construction and change of occupation, among others. However, the coverage of EPCs is still limited, and a small percentage of the building stock have an EPC. In addition, there are certain difficulties in the management of the EPCs by administrations which occasionally make it difficult to take advantage of the data contained in the EPCs.
As of the approval of Royal Decree 47/2007 the first EPCs for new buildings in Asturias began to be registered. Subsequently, from Royal Decree 235/2013 , the EPCs corresponding to existing public and private buildings began to be registered. As of the year 2022, 139,000 EPCs have been issued in the Official Register of Asturias.
It is essential to have tools that allow to streamline the application process and the extraction of useful information ranging from the identification and correction of outliers to the verification of the coherence of data and the global results. The overall objective of this process would be the use of the information contained in the EPCs for the design of building energy retrofitting strategies and policies. Bearing this in mind, and within the collaboration framework of the INERGY Project, FAEN and CARTIF are working together on the creation of several AI-based tools to achieve the aforementioned improvements.
The first tool that is being developed consists of an EPC’s checker in XML format. This allows the user to check whether the information in the EPC is correct and specific key parameters included therein don’t exceed certain limits. This can be done in two ways: by uploading the file itself or by selecting one from a database (which currently contains the Asturias’ EPCs from 2016 to 2018). Then, the tool “checks” the EPC and provides general information on the EPC checked, as well as information on each of the EPC data categories (e.g. Building identification, General building data and geometry, Building envelope data, Building thermal energy systems’ data, etc.). These categories appear in red or green, depending on the result of the check, with a number at the right to inform on the number of fields “checked” in each and the number of errors or unexpected values. The user can display each of the categories and then open the drop-down menus to visualise all the information contained within such category.
Although all information is shown for a better understanding of the certificate and for comparison purposes, not all values are checked. There are different approaches to check the parameters contained in the EPCs, depending on the type of value. Firstly, some values are checked in terms of (1) coherence (e.g. the address is checked with cadastre, the post code is checked with the municipality postal code, etc.), while other parameters are (2) contrasted with normative values and type of element (considering the limitations of the Spanish Building Code in force at the time of its construction). Moreover, some parameters are checked based on (3) outlier values (derived from the analysis of the values in all EPCs in the database), and other parameters are checked (4) according to their interdependence from others or (5) according to ranges/lists of expected values.
For each of the values checked, the tool provides a message of “expected value” or “unexpected value”, for this second answer, the tool provides more information on the type of check performed. The tool is intended to serve as a warning system so that the EPC manager can examine the certificate and decide what kind of action must be implemented.
The second tool based on the information from Asturias’ EPCs consists on an EPCs and estimated energy demand viewer. This tool allows users to visualise heating and cooling energy demand, energy consumption and CO2 emissions in municipalities. This is offered at building level, and at higher levels of aggregation. The information is shown as a coloured map, with colours assigned to each building based on their EPC label (from A to G, from green to red). The user can select if they want to see the labels for non-renewable primary energy, for CO2 emissions, for heating demand and for cooling demand. The visualisation provides also information on the average labels for the area showed in the map.
When moving the mouse around the map, pop-up messages appear for each of the buildings providing information on the cadastral reference and the value for the selected indicator to colour the map (from those four mentioned above). Then, if the user clicks on a specific building, the tool provides also more detailed information on the key information of the building (i.e. cadastral reference, climate zone, total surface, average height, current use, typology, year of construction and number of dwellings), as well as on the average geometry characteristics (i.e. external facade surface -and per facade according to the four orientations-, party walls surface, surface roof, volume above ground and compactness).
The estimated values displayed are calculated according to an approach on estimated values based on real EPCs. And the following information is provided for each building: non-renewable primary energy, CO2 emissions, heating demand and cooling demand; as well as more detailed information on emissions (heating emissions, cooling emissions and DHW emissions) and on non-renewable primary energy (on the three same parameters as for the emissions).