This paper presents the results of measuring the final energy consumption for heating and domestic hot water (DHW) preparation and indoor conditions in 15 apartments located in pre-war tenement houses. The measurements were compared to the computed energy consumption. The calculations ware made based on the model calibrated by field measurements. The discrepancies between measurements and calculations were assessed using the energy performance gap (EPG). Calculations were made separately for energy for heating and for DHW preparation. Additionally, the results of EPG calculations for different levels of analysis are presented aiming at assessing the impact of weather, temperature in the surrounding zones and users’ behavior. Users’ behaviors influencing the size of the EPG were divided into typical (energy saving or excessive energy consumption) and forced (energy poverty, response to the apartment’s surroundings, technical limitations. The connection between the heating sources and the heating habits has been clearly observed in the research. The former (typical) behaviors were the origin of the energy gap in the apartments heated with natural gas and district heating. The latter (forced) were the origin of the gap in the apartments heated with mostly electricity and solid fuel (with one exception: one apartment that utilized the district heating).

Of all the European Union's member states, Poland has the most acute ambient air pollution problem. An urgent transition from solid-fuel heating (e.g. coal and wood) in the housing sector is required to improve air quality in the country. National regulations still allow the sale of solid fuels for heating, but some municipalities impose local resolutions with binding deadlines for solid-fuel bans. A realworld study covering 422 apartments in heritage tenements in Wrocław is presented. A link between domestic solid-fuel usage and tenure type is identified: solid fuels prevail in social housing. The transition to other forms of heating will adversely affect the inhabitants already vulnerable to fuel poverty. Solid fuel proves to be the least preferred heating option and is linked to substandard living conditions. Fuel poverty vulnerability for low-income households is established based on cost analysis for different heating options, thermal retrofit strategies, internal temperatures and apartment sizes. The results indicate that climate injustice is likely to occur for the poorest inhabitants due to their inability to afford increased costs. Policy implications to address this injustice are needed to ensure the transition from solid-fuel heating will avoid new vulnerabilities. Policy relevance Domestic solid-fuel combustion for heating purposes is linked to poor air quality in urban areas in Poland. Heritage tenements are the most technically deprived building stock and their inhabitants are already vulnerable to fuel poverty. To improve air quality and respond to climate change, solid fuels need to be substituted with less polluting but more expensive heating options. Potential climate injustice (harm) is likely to occur if the poorest inhabitants cannot afford to heat their homes due to a ban on solid fuels. The change of heating needs to be combined with additional support (thermal retrofit and appropriate pricing of alternative fuels). Air quality-driven polices focused on solid-fuel eradication should not ignore fuel poverty already experienced mainly by social housing residents using expensive electric heating on a standard tariff. Fuel poverty has a gender aspect related to the gender pay gap that needs addressing.

E3S Web of Conferences, open access proceedings in environment, energy and earth sciences

This paper presents the results of measuring and calculating the final energy consumption for heating and domestic hot water preparation in six apartments located in pre-war tenement houses in Wroclaw (Poland). The calculations were carried out based on energy models of dwellings calibrated with measurement data. Calculation variants were characterized by seven internal parameters (indoor air temperature, heat transfer coefficient by transmission through the internal partition, internal heat gains, air exchange multiplicity in the dwelling, domestic hot water consumption, and domestic hot water temperature and cold water temperature) and two external parameters (outdoor air temperature and insolation). By comparing calculations with measurements, the energy performance gap (EPG) values associated with each parameter were determined. The presented results indicate how much of the differences could be attributed to weather conditions and how much to other factors. It is quite common for the influence of some factors to cancel out the influence of others. Identifying and understanding the real causes of the energy gap may allow for the proposal of better retrofitting solutions or appropriate financial support to households at risk of energy poverty. It is important to note that only in-depth interviews with residents and measurements, such as those carried out in this case, allow such situations to be identified in detail.

Operating in part-load conditions significantly affects the energy efficiency of the air-to-water heat pumps. The currently used method of testing the devices does not provide the necessary data for estimating the degradation of the device’s efficiency in part-load operating mode. The value of the degradation coefficient Cc = 0.9 adopted in accordance with the EN 14825 standard is generally used. However, this value often does not reflect the actual degree of the COP reduction. Hence the new quasi-dynamic model and the calculation approach to the degradation coefficient were proposed. The model reflects the real and overall reduction between the full and part-load COP, not only the energy consumption in the stand-by mode. The estimation was made using the field measurement data of the air-to-water heat pump supplying heat to the low temperature installation. It has been proved that the determination of the main parameter is possible using a relatively small amount of data without losing an accuracy.

The energy efficiency of air-to-water heat pump operating in an actual heating installation depends on many factors. In order to create a reliable model of the unit, it is necessary to include as many of them as possible. Unfortunately, the most common data provided by heat pump manufacturers are based on tests performed in accordance with the EN 14511 standard [1]. These tests are performed in steady-state conditions and do not provide reliable information on the impact of dynamic effects on the energy efficiency of the device. The solution may be the tests in quasi-dynamic conditions. The article presents the possibility of creating the characteristics of an air-to-water heat pumps based on operational data. The accuracy of the created model has been compared with the characteristics resulting from measurements in steady state conditions. It has been confirmed that dynamic test data, after proper selection, will allow to determine the characteristics of repeatable parameters and this can be an alternative to tests performed in fixed conditions.