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Purpose Understanding the dynamic hygrothermal behavior of building elements is very important to ensure the optimal performance of buildings. The Laboratory for Quality Control in Buildings of the Basque Government tested a flat roof designed by a construction company that developed a building to be constructed using prefabricated modules. This is a five to eight floor building with ventilated façade and a flat roof covered by gravel with the possibility of changing it to a green cover. The paper aims to discuss this issue. Design/methodology/approach The interest of this research was threefold. The first objective was to accurately test, under real dynamic weather conditions, the roof design in a PASLINK test cell to obtain the U-value and the thermal capacitance of the different roof layers, and of the roof as a whole, through the precise calibration of resistance-capacitance mathematical models of the roof. Based on the parameters and experimental information of these calibrated models, a second goal was to calibrate and validate a Wufi model of the roof. Findings This second calibrated model was then used to simulate the dynamic hygrothermal behavior of the roof, obtaining the roof’s hourly thermal demand per square meter for a whole year in different locations considered in the Spanish Building Code. These simulations also permitted the authors to study the risk of condensation and mold growth of the tested component under different climatic conditions. Originality/value The successful combination of the PASLINK method to calibrate the Wufi hygrothermal model is the main novelty of this research.

Vacuum insulation panels (VIPs) represent a huge opportunity to achieve nearly zero energy buildings, especially in the retrofitting of existing buildings. VIPs can be applied in conjunction with façade cladding elements, considerably reducing the heat losses or gains from the building by means of very slim wall construction systems or retrofit solutions. However, the fact that VIPs cannot be cut on-site, can be easily damaged during their handling, installation and use and have an envelope that can cause thermal bridging in the junction between panels or when combined with other materials, has hindered their penetration in the construction market. This paper presents two innovative façade retrofitting solutions, a rear ventilated façade and a stud mounted internal solution, that have tackled all these issues and provide thermal transmittances of 0.28 and 0.14 W/m2 K in relatively slim insulation systems of 10 cm widths. Solutions have been installed on the entire façade of two existing buildings located in Bilbao (Spain) and Malmö (Sweden) subjected to an integral rehabilitation process, covering 2100 m2. Buildings energy use have been monitored before and after the renovation, showing energy cuts of around 35% from pre-intervention status. This paper presents the lessons learnt during the design and installation process of the vacuum insulation integrating solutions in the façade of two existing buildings and the thermal performance results achieved after their retrofitting. Thanks to A2PBEER project for providing the resources. This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 609060. This paper reflects only the author’s views and the Union is not liable for any use that may be made of the information contained there in.

The performance gap between the design energy consumption of buildings and their real energy consumption has three main sources: the energy systems’ performance, the users’ behaviour and the buildings’ envelope performance. The latter should be characterized under in-use conditions by estimating their in-use Heat Loss Coefficient (HLC). This work further develops an existing ‘average method’ by fully developing it from the energy conservation principle applied to a generic in-use building. Furthermore, the uncertainty sources are identified and limited through the mathematical development of the method. An innovative solution to the problematic of multizone buildings is also demonstrated, where HLC values should be calculated for different floors and then aggregated to obtain the entire building's HLC. Furthermore, all these can be done without the need of a detailed model of the building. The improved average method has been applied to an occupied, energetically monitored office building of the University of the Basque Country. The building was energetically rehabilitated during the summer of 2017. Therefore, the proposed method has been applied over the three winters prior to rehabilitation and then, to the winter after the rehabilitation. It has thus been possible to estimate a 28% reduction of the HLC for the post-retrofitted case, as compared to the pre-retrofitted one.

The aim of this study is to accurately simulate the thermal performance of a PASLINK test cell with a gravel covered roof test component using a methodology that combines dynamic simulation and mathematical techniques . The main contribution of this work is a new method that improves the characterization of building models used in simulation software for the evaluation of energy demands and savings. The methodology consists on TRNSYS dynamic simulation, MOAT (Morris one-at-a-time) and BACCO (Bayesian analysis of computer code output) sensitivity analysis and a Bayesian calibration. These techniques are applied to a test cell with high quality monitoring data that validate the simulation performance. The results demonstrate the benefits of these techniques in reducing the coefficient of variation of the root mean square error , CV(RMSE), between the simulated internal temperature and the real temperature to a value less than 3.38% under different load conditions. Therefore, the calibrated models obtained with this method can considerably reduce the gap between the simulation and real performance of buildings.

Supercritical CO2 cycles have been said to be a good alternative to the Rankine Cycles for Concentrating Solar Power plants of the future. The next generation molten salts will be able to achieve 700 °C, which is a suitable temperature for Supercritical CO2 cycles. However, there is a big uncertainty about the efficiencies of the cycle components, which could make these cycles unviable. A sensitivity analysis of the energy efficiency of the Recompression Cycle and Partial Cooling Cycle, regarding turbomachinery isentropic efficiencies and Recuperator effectiveness variations, has been carried out to show that the Recompression Cycle’s energy efficiency is considerably more sensitive than the Partial Cooling Cycle’s. From the sensitivity analysis, it can also be concluded that the Recompression Cycle is the best performing cycle for most of the studied cases, with energy efficiencies in the range between 32.97% and 51.91%. Exergetically, the Recompression Cycle is also more suitable in most situations, and the exergy analysis on cycle components shows that irreversibilities occur mainly in the Recuperators, which means that future research should focus on methods to reduce irreversibilities in these components. The state-of-the-art of Supercritical Rankine Cycle plant net energy efficiencies currently reach 45.60% for fossil fuel plants. Although Supercritical CO2 cycles are a simpler and more compact alternative, this work concludes that only the optimized Recompression Cycle with turbomachinery isentropic efficiencies over 92% and Recuperator effectiveness over 95% are able to obtain similar or higher efficiencies than actual Supercritical Rankine Cycles. Furthermore, the sensitivity analysis plots permit the areas to be mapped where each of the optimized two-cycle efficiencies can compete with the Supercritical Rankine Cycles regarding the turbomachinery isentropic efficiencies and Recuperator effectiveness.

The existing performance gap between the design and the real energy consumption of a building could have three main origins: the occupants’ behaviour, the performance of the energy systems and the performance of the building envelope. Through the estimation of the in-use Heat Loss Coefficient (HLC), it is possible to characterise the building’s envelope energy performance under occupied conditions. In this research, the estimation of the HLC of two individual residential buildings located in Gainsborough and Loughborough (UK) was carried out using an average method. This average method was developed and successfully tested in previous research for an occupied four-story office building with very different characteristics to individual residential buildings. Furthermore, one of the analysed residential buildings is a new, well-insulated building, while the other represents the old, poorly insulated semidetached residential building typology. Thus, the monitored data provided were filtered in order to apply the abovementioned average method. Even without fulfilling all the average method requirements for these two residential buildings, the method provides reliable HLC values for both residential buildings. For the house in Gainsborough, the best estimated HLC value was 60.2 W/K, while the best approach for Loughborough was 366.6 W/K. Thus, despite the uncertainty sources found during the analysis, the method seems promising for its application to residential buildings. This work was supported by the Spanish Ministry of Science, Innovation and Universities and the European Regional Development Fund through the MONITHERM project “Investigation of monitoring techniques of occupied buildings for their thermal characterization and methodology to identify their key performance indicators”, project reference: RTI2018-096296-B-C22 and -C21 (MCIU/AEI/FEDER, UE).

Hospitals present a widely recognized margin for energy conservation due to their elevated final energy use intensity. Specifically, operating rooms are among the functional areas with greatest energy demand in hospitals, given the stringent indoor conditions for patients and surgical staff. However, energy efficiency in surgical facilities has traditionally been overlooked by the scientific literature in favor of guaranteeing adequate air quality conditions. This paper assesses the potential energy savings that could be achieved in a surgical suite in a Spanish hospital by lowering the current ventilation rates to the lowest energy-demanding values recommended by the proper Spanish standard and other international codes. Likewise, the paper assesses the actual hygrothermal and ventilation conditions in the suite based on the results of a continuous monitoring campaign performed for a period of 12 days. Simulations undertaken with a dynamic energy model specifically developed and calibrated for this work revealed that the average energy intensity of the suite is 1021 kWh/m2/year (1685 kWh/m2/year for operating rooms), with 80% of the total annual thermal demand corresponding to periods of inactivity. In addition, energy savings between 40% and 80% are possible while complying with both national and international standards.

[EN]The actual building energy performance essentially depends on the building occupant's behaviour, the real performance of the installed energy systems and the in-use performance of the building envelope. The thermal performance characterization of in-use building envelopes, based on monitored data, represents a crucial step towards bridging the gap between the designed and as-built energy performance of buildings. The main indicator to analyse the performance gap of building envelopes is the Heat Loss Coefficient (HLC); when measured, it commonly shows considerable differences when compared with the design value. This research goes further and proposes a method, based on monitored data from in-use buildings, for the decoupling of the HLC of in-use buildings into its transmission (UA) and infiltration (C-v) heat loss coefficients, in order to identify the origin of the heat losses. The identification of this origin will facilitate the reduction of the performance gap. Therefore, a multi-storey occupied office building of the University of the Basque Country has been monitored and analysed, where the in-use HLC for each floor and for the whole building have already been estimated using an average method. Then, based on the ASTM D6245-18 Standard, the decay method of the metabolic CO2 of the building's occupants has been successfully applied in this paper to obtain the Air Change per Hour (ACH) rates due to infiltrations. These ACH values have been used to decouple the estimated HLC values into their transmission and infiltration parts. This work was supported by the Spanish Ministry of Science, Inno-vation and Universities and the European Regional Development Fund (grant number RTI2018-096296-B-C22) through the MONITHERM project 'Investigation of monitoring techniques of occupied buildings for their thermal characterization and methodology to identify their key performance indicators', project reference: RTI2018-096296-B-C22 (MCIU/AEI/FEDER, UE) . The corresponding author also acknowledges the support provided by the Education Department of the Basque Gov-ernment through a scholarship granted to her to complete her PhD degree.

Buildings are expected to be energy efficient but also to provide a comfortable environment to their occupants as well as to be durable. Indoor relative humidity influences the energy consumption, structure and the occupants’ comfort and health. Therefore, it is necessary to control and predict indoor environmental conditions. This work aims to simulate indoor temperatures and relative humidity in a multi-zone building model under realistic conditions, such as occupancy and moisture gains, operation of windows and doors and mechanical ventilation. The combined multi-zone air flow model is developed with TRNSYS and TRNFLOW and it is applied to a phase of the Twin Houses extended experiment of the international energy agency, energy in buildings and communities (IEA EBC) Annex 71. The main novelty of this work is to determine the masses of surface and deep moisture buffer storage by performing a multi-objective calibration of indoor temperatures and relative humidity. Results prove that building energy simulations need to model the moisture buffering of internal materials to accurately predict indoor humidity. The error in simulating relative humidity is reduced by 69% in the house with moisture gains after calibration of the masses of buffering materials. Moreover, the calibrated multi-zone building model shows a great agreement between simulated and measured data with an average root mean square error (RMSE) among thermal zones of 0.51 °C and 0.48 °C in indoor temperatures and 3.58% and 2.21% in relative humidity for the two houses in the validation period.

Street lighting plays an important role in the comfort and safety of drivers and pedestrians, so the control and management of the lighting systems operation and consumption is an essential service for a city. In this document, a methodology is presented to calibrate lighting models in order to assess the lighting performance through simulation techniques. The objective of this calibration is to identify the maintenance factor of the street lamps, determine the real average luminance coefficient of the road pavement and adapt the reflection properties of the road material. The method is applied in three stages and is based on the use of Radiance and GenOpt software suits for the modeling, simulation, and calibration of lighting scenes. The proposed methodology achieves errors as low as 13% for the calculation of illuminance and luminance, evincing its potential to assess the actual lighting conditions of a road. Ministerio de Ciencia, Innovación y Universidades | Ref. FPU17/01834

There is an increasing interest in reducing the energy consumption in buildings and in improving their energy efficiency. Building retrofitting is the employed solution for enhancing the energy efficiency in existing buildings. However, the actual performance after retrofitting should be analysed to check the effectiveness of the energy conservation measures. The aim of this work was to detect and to quantify the impact that a retrofitting had in the electrical consumption, heating demands, lighting and temperatures of a building located in the north of Spain. The methodology employed is the application of Functional Data Analyses (FDA) in comparison with classic mathematical techniques such as the Analysis of Variance (ANOVA). The methods that are commonly used for assessing building refurbishment are based on vectorial approaches. The novelty of this work is the application of FDA for assessing the energy performance of renovated buildings. The study proves that more accurate and realistic results are obtained working with correlated datasets than with independently distributed observations of classical methods. Moreover, the electrical savings reached values of more than 70% and the heating demands were reduced more than 15% for all floors in the building. This paper was funded by the Spanish Government (Science, Innovation and Universities Ministry) under the project RTI2018-096296-B-C21.

Computer vision is used in this work to detect lighting elements in buildings with the goal of improving the accuracy of previous methods to provide a precise inventory of the location and state of lamps. Using the framework developed in our previous works, we introduce two new modifications to enhance the system: first, a constraint on the orientation of the detected poses in the optimization methods for both the initial and the refined estimates based on the geometric information of the building information modelling (BIM) model, second, an additional reprojection error filtering step to discard the erroneous poses introduced with the orientation restrictions, keeping the identification and localization errors low while greatly increasing the number of detections. These enhancements are tested in five different case studies with more than 30,000 images, with results showing improvements in the number of detections, the percentage of correct model and state identifications, and the distance between detections and reference positions.

Due to the European Union energy reduction strategy, many in-use buildings will be energetically monitored in the coming years to obtain their main thermal characteristics to improve or prove their energy efficiency. This is difficult to do with a reduced set of sensors and a robust data analysis methodology. This paper is focused on proposing some modifications on the existing ISO 9869 method and co-heating method to make them usable with basic energy monitoring data of in-use buildings and obtain their main thermal characteristics: the Heat Loss Coefficient (HLC considers heat losses through envelope plus infiltration) and the solar aperture (Sa or gA-value) of the whole building. Under the FP7 project A2PBEER an occupied big office building has been energetically monitored. This monitoring system has been designed and installed while the building was in operation. Using this monitored data a modified ISO 9869 method has been applied to some specifically selected cloudy and cold winter periods to obtain the HLC of the building. Taking this HLC as a reference, a modified co-heating method has been used to estimate both the HLC again and the Sa of the whole building. Although monitoring was carried out under very difficult conditions since the building was occupied, the proposed modifications on those two existing methods have delivered very reliable results with these two Key Performance Indicators (HLC and Sa) of the building under real operation conditions.

The thermal characterization of building components in dynamic exterior conditions is crucial for understanding their real performance, particularly if they are passive or active solar elements. In this respect, the PASLINK methodology has stood out as an effective technique for outdoor testing due to its level of development and precision. It is based on the use of a calibrated test cell with interior walls covered by heat flow meters. The accurate determination of the heat flow through the envelope of the cell is essential for the subsequent thermal analysis of the passive/active solar component being tested. Although the walls of a PASLINK cell have a high thermal resistance and minimal thermal bridges, a higher heat flux is inevitable near the inner corners because of the edge effects. This variation is partially detected by heat flow meters, requiring correction factors accordingly named ‘edge effect factors’. Additional heat flow meters strategically arranged in some interior corners are used to determine these factors in a calibration test. The factors thus calculated are used as invariable values in subsequent cell tests. However, the skill and knowledge of the staff conducting the calibration test are fundamental, as human errors can affect this process. This proposal outlines a more objective and reliable new methodology to determine edge effect correction factors. It is based on applying correlations of instantaneous readings of heat flow meters. These correlations are obtained in an initial PASLINK calibration test, but are valid for all subsequent tests. The factors calculated in this way depend on instantaneous test readings and, for this reason, they are dynamic values perfectly adapted to each test. The calibration test of the cell called EGUZKI, located in Vitoria-Gasteiz (Northern Spain), is used to demonstrate the validity of the proposed method. With the current PASLINK calibration test methodology, the calibrated cell obtains a measurement error of 13%, while the proposed new dynamic methodology reduces this error to 6%. Although this new methodology is determined in the context of a PASLINK test cell, it is an extensive method applicable to the correction of heat flow measurements affected by edge effects in general.

Hybrid systems for space heating and Domestic Hot Water (DHW) production are an attractive option for buildings to decrease their CO2 emissions. In this research, the operation variables of an installation, composed of a Stirling engine, a condensing boiler and a thermal storage tank, were optimized to supply heating and DHW demands of a virtual detached house. For this purpose, in an experimental installation operated with common control set points, the hybrid system was tested during the week of highest demand. Then the installation was modelled in TRNSYS, calibrated and validated against the experimental data and, finally, different multi-objective optimizations were carried out on the model to optimize the operation set points. The results obtained show that solely by optimizing the control variables of the calibrated model of the actual installation gives a reduction of 7% in cost and an improvement of 3.9% in exergy efficiency. Thus, it can be concluded that simply optimizing control variables in this type of hybrid systems can lead to low cost reductions. By reducing the thermal losses of the calibrated model from the experimental 17% of energy consumed to 5% and then optimizing it, a reduction of 17% in cost and an improvement of 23% in exergy efficiency were obtained. Different model insulation levels were tested, and two interesting conclusions were found from this analysis: until the level of transmission losses is below 5% of the energy consumed, the optimized operation conditions lead to a negligible use of the thermal storage, after which it increases drastically. On the other hand, it can be concluded that the cost optimization that optimizes the adiabatic model of the analysed hybrid system is insensitive to the selected control variables.

New construction buildings should consider high efficiency energy systems according to European Directives. An optimized micro-cogeneration system is an effective solution to improve the energy efficiency of the residential sector. For this reason, this work presents a novel method to model and optimize a micro-cogeneration based on a natural gas internal combustion engine. The facility, which is located in an experimental plant, provides the equivalent domestic hot water and heating demand of three single-family dwellings. The main aim of this work is to optimize the cost and exergy efficiency of the facility. First, the micro-cogeneration is modeled in TRNSYS. Then, Morris sensitivity analysis is used to detect the model variables for a posterior calibration with experimental data. The employed calibration method is a multi-objective optimization of the error functions between simulated and measured data with the NSGA-II algorithm. After the calibration, optimization with NSGA-II is applied again to the control variables of the model to minimize the cost and to improve the exergy efficiency. The optimized performance produces a daily cost reduction of 24.5%, an exergy efficiency improvement of 21% and a gas consumption decrease of 15%. We also demonstrate the importance of addressing the facility inertia in the models to obtain accurate simulation outputs. The novelty of this work is to present a methodology to optimize the exergoeconomic performance of micro-cogeneration systems by model calibration and optimization using multi-objective optimization with genetic algorithms.

The present article investigates the question of building energy monitoring systems used for data collection to estimate the Heat Loss Coefficient (HLC) with existing methods, in order to determine the Thermal Envelope Performance (TEP) of a building. The data requirements of HLC estimation methods are related to commonly used methods for fault detection, calibration, and supervision of energy monitoring systems in buildings. Based on an extended review of experimental tests to estimate the HLC undertaken since 1978, qualitative and quantitative analyses of the Monitoring and Controlling System (MCS) specifications have been carried out. The results show that no Fault Detection and Diagnosis (FDD) methods have been implemented in the reviewed literature. Furthermore, it was not possible to identify a trend of technology type used in sensors, hardware, software, and communication protocols, because a high percentage of the reviewed experimental tests do not specify the model, technical characteristics, or selection criteria of the implemented MCSs. Although most actual Building Automation Systems (BAS) may measure the required parameters, further research is still needed to ensure that these data are accurate enough to rigorously apply HLC estimation methods. This work was supported by: Spanish Economy and Competitiveness Ministry and European Regional Development Fund through the IMMOEN project: "Implementation of automated calibration and multiobjective optimization techniques applied to Building Energy Model simulations by means of monitored buildings". Project reference: ENE2015-65999-C2-2-R (MINECO/FEDER); European Commission through the A2PBEER project "Affordable and Adaptable Public Buildings through Energy Efficient Retrofitting". Grant agreement No.: 609060; Laboratory for the Quality Control of Buildings (LCCE) of the Basque Government; University of the Basque Country (UPV/EHU). Framework agreement: Euro-regional Campus of Excellence within the context of their respective excellence projects, Euskampus and IdEx Bordeaux. Funder reference: PIFBUR 16/26.