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For scaling renovation, there is a need for assessing the energy performance of buildings at the neighborhood level. Traditional methods for assessing individual buildings are manual and time-consuming – not sufficient to enable the neighborhood level assessment of the energy performance of buildings. Instead, new methods based on existing data in national registries and building typologies are required. The aim in this article is to develop for obtaining necessary initial building geometry information for energy performance calculations from the Estonian national Building Registry (EBR), including also Digital Twin (LOD) geometric models of buildings, and the quality and accuracy of this data is assessed. Altogether 417 representative buildings were used for qualitative and quantitative analysis. A sub-sample of 41 buildings were selected for more detailed analysis and development of methods. Two methods were developed to extract and enrich initial building geometry information for energy performance calculations: (a) the method combining the EBR and building reference data; and (b) the method combining the EBR and building typology data and LOD models of apartment buildings. The estimated accuracy of the first method (a) is around 98% and the second method (b) around 94%. Both methods underestimate the actual envelope area and thermal bridge lengths.

Direct comparison of building energy performance levels between countries is usually not possible due to differences in climatic conditions, calculation methods, primary energy (PE) factors and input data. The aim of this paper is to analyse the differences in nearly zero energy office buildings requirements and energy calculation methodology in Denmark, Finland, and Estonia. The study is based on a newly built Estonian office building, designed to meet national NZEB requirements. To account for the climatic differences between the countries a heating-degree-days-based correction factor was applied for building envelope thermal transmittance. NZEB requirements for each country are compared with European Commission (EC) recommended values (EU 2016/1318) using normalization and benchmarking through detailed computer simulations. National NZEB primary energy threshold was needed to be reduced by 7% in Denmark and by 23% in Estonia to meet EC recommendations. At the same time, the flagship reference building, that was better than Estonian NZEB, met both Nordic and Oceanic EC recommendations. Finnish NZEB requirement was not exceeded with any building configuration applied in this study, indicating that Finnish NZEB is considerably less strict compared to Danish and Estonian ones.

In this study the cost changes caused by the implementation of the nZEB solutions are calculated. The energy demand of a building was calculated according to the methodology for calculating the energy efficiency of buildings, using dynamic energy simulations. The financial calculations are based on the methodology described in Delegated Regulation (EU) No 244/2012 of the European Commission. The simulations and calculations for assessing the cost-effectiveness of technical solutions are based on the selected sample building. The energy efficiency solutions are derived by increasing/decreasing the insulation value of the building envelope in subsequent steps. Financial calculations were based on the investment needed to achieve the nearly zero-energy levels. The results for different combinations vary to a large degree. According to regulations new building must fulfill the low energy building (EPI class “B”) requirement without local production. The EPI value to fulfill the requirement in the cost-even range is reached in case of the GSHP and efficient DH. In case of the GSHP and efficient DH also the cost-optimal point is in the EPI class “B”. Overall the minimum ΔNPV values stay below the zero line in all the cases offering a range of opportunities to choose combinations to reach lover EPI compared to base case. The results of cost-effectiveness calculations for selected building with different combinations of structural solutions and heat sources show the possible different scenarios to reach nZEB level and the possible cost reduction.

In the member states of the European Union (EU), nearly-Zero Energy Buildings (nZEB) are becoming mandatory building practice in 2021. It is stated, that nZEB should be cost-optimal and the energy performance levels should be re-defined after every five years. We conducted cost-optimality analyses for two detached houses, one terraced house and one apartment building in Estonia. The analysis consisted on actual construction cost data collection based on bids of variable solutions for building envelope, air tightness, windows, heat supply systems and local renewable energy production options. For energy performance analysis we used dynamic simulation software IDA-ICE. To assess cost-effectiveness, we used Net Present Value (NPV) calculations with the assessment period of 30 years. The results for cost-optimal energy performance level for detached house with heated space of ~100 m2 was 79 kWh/(m2 a), for the larger house (~200 m2) 87 kWh/(m2 a), for terraced house with heated space of ~600 m2 71 kWh/(m2 a) and for the apartment building 103 kWh/(m2 a) of primary energy including all energy use with domestic appliances. Thus, the decrease in cost-optimal level in a five-year period was ~60% for the detached house and ~40% for the apartment building, corresponding to a shift in two EPC classes.

This study presents the assessment of actual indoor climate condition and energy performance in eight NZEB school and daycare centers of NERO H2020 project. Physical parameters such as indoor temperature, relative humidity, CO2, airflow rate and temperature were measured during heating and cooling seasons, in parallel with an occupants’ questionnaires survey. Besides, calculated and measured energy data was collected from energy performance certificates and energy bills. Thermal comfort and IAQ were assessed based on categories in EN15251 standard with color footprints. Results showed that all the buildings had good or excellent indoor climate during the heating season. However, a large percentage of occupied hours were categorized as category IV during the cooling season, which mainly occurred due to too low indoor temperature caused by the low outdoor temperature during the measurement period. Also, all buildings achieved low CO2 levels. Moreover, the conducted questionaries’ survey showed good correlation with measured results for all buildings except in one building, which had odor and noise problems. In contrast, the measured energy use in 5 buildings out of 7 was increased by factor 2.1-3.0 compared to calculated annual energy use due to a full-time operation of the ventilation system and presence of hot kitchens.