Classifying system for façades and anomalies

Façades play an important role in buildings’ energy demand, and their state of conservation obviously influences thermal performance. The energy performance gap in existing residential buildings due to façade conservation status has not been analyzed in depth. In order to facilitate the systematic analysis of this influence, a system for classifying façades and their corresponding anomalies was developed for the first time. The classification system includes 23 types of façades and eight types of anomalies. It was verified by a panel of experts, and a case study was carried out with a sample of 154 buildings. An analysis of the results showed that the classification system is useful for a future analysis of the energy performance gap in existing residential buildings.Peer ReviewedPostprint (author's final draft

Review of criteria for determining HFM minimum test duration

The actual thermal behaviour of façades is important to identify suitable energy-saving measures and in- crease the energy performance of existing buildings. However, the accuracy of in situ measurements of façades’ U-values varies widely, mostly due to inadequate test durations. The aim of this paper was to evaluate the minimum duration of in situ experimental campaigns to measure the thermal transmittance of existing buildings’ façades using the heat flow meter method, and to analyse the thermal performance of the façade during the test. Minimum test duration was determined according to data quality criteria, variability of results criteria, and standardized criteria for different ranges of theoretical thermal trans- mittance and for the same range of average temperature difference. Then, the minimum test duration results were compared. The findings show that ISO criteria are more sensitive and provide more accurate results, requiring a longer test duration. However, when certification is not required, the duration of the test could be reduced by applying data quality and variability of results criteria. The minimum duration of experimental campaigns depends on the theoretical thermal transmittance and the stability of climatic conditions. Moreover, results are more accurate when the dynamic method is used.Peer ReviewedPostprint (author's final draft

A comparison of standardized calculation methods for in situ measurements of facades U-value

In recent years, a growing concern has been how to determine the actual thermal behaviour of façades in their operational stage, in order to establish appropriate energy-saving measures. This paper aims at comparing standardized methods for obtaining the actual thermal transmittance of existing buildings’ façades, specifically the average method and the dynamic method defined by ISO 9869-1:2014, to verify which best fits theoretical values. The paper also aims to promote the use of the dynamic method, and facilitate its implementation. Differences between the theoretical U-value and the measured U-value obtained using the average and dynamic methods were calculated in three case studies, and then compared. The results showed that differences between the theoretical and the measured U-value were lower when the dynamic method was used. Particularly, when testing conditions were not optimal, the use of the dynamic method significantly improved the fit with the theoretical value. Moreover, measurements of the U-value using the dynamic method with a sufficiently large dataset showed a better fit to the theoretical U-value than the results of other dynamic methods proposed by authors. Further research should consider the optimum size of the dataset to obtain a measured U-value that is correctly adjusted to the theoretical U-value.Peer ReviewedPreprin

Optimal ventilation strategies for balancing indoor air quality, comfort and energy use in educational buildings. The IAQ4EDU project.

Currently, there is great concern about adequate indoor ventilation to prevent adverse effects on occupants’ health, and, within educational buildings, to ensure students and professors’ well-being and improve learning processes. This paper aims to present an innovative framework, developed within the IAQ4EDU project, to improve the effectiveness of the ventilation strategies in educational centres considering the indoor air quality, thermal comfort, energy consumption and global costs. This consists on characterise indoor air quality, simulate building ventilation strategies using reduced order models and develop multi criteria decision making method. 40 classrooms located in 20 Spanish educational buildings are used as case study.This research is part of the Catalan agency AGAUR under their research group support programme (2017SGR00227).Peer ReviewedObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No ContaminantObjectius de Desenvolupament Sostenible::3 - Salut i BenestarObjectius de Desenvolupament Sostenible::4 - Educació de QualitatPostprint (published version

Life-cycle environmental and cost-effective energy retrofitting solutions for office stock

The European Green Deal establishes the need to renovate buildings in an energy efficient way, to address climate and environmental challenges. The purpose of this study was to devise a model for identifying environmental, cost-effective retrofitting measures by assessing their energy, economic and environmental impact when they are applied to the entire office stock. The methodology builds upon the energy performance certificate scheme to identify the life-cycle energy, economic and environmental impacts of a set of energy renovation measures for each representative office. The results can then be applied to the entire office stock. For any real office, a dozen characteristics are entered. Then, a user-friendly interface provides information about the expected performance of the renovation measures in that case along with the representativeness of the results. This methodology was implemented in a Spanish case study of 13,701 energy performance certificates. The findings showed that the most efficient energy renovation measures are heat pump replacement (18.1%) and replacement of lamps with LEDs (14.4%). Although the most effective retrofitting solutions depended on the evaluation criteria (energy, economic or environmental), 99.5% of the cost-effective measures also reduced emissions during the life cycle.This research was supported by the Spanish Ministry of Economy,Industry and Competitiveness under R&D project EOFF, reference no.BIA2016-75382-R (AEI/FEDER, UE). The Catalan Institute of Energy(ICAEN) is gratefully acknowledged for allowing access to the energy performance certificates database.Peer ReviewedPostprint (published version

Assessing the impact of the COVID-19 lockdown on the energy consumption of university buildings

Exceptional pandemic lockdown measures enabled singular experiments such as analysing the energy consumption of vacant buildings. This paper assesses the impact of the COVID-19 lockdown on the energy use of academic buildings. For this purpose, weather-adjusted energy use was compared before and during the lockdown, including different levels of lockdown restrictions. Results obtained for the 83 academic buildings of Universitat Politècnica de Catalunya - Barcelona Tech (UPC) reveal that the avoided energy consumption amounted to over 4.3 GWh during the post-pandemic year. However, the results indicate that academic buildings were still using approximately 46.9% of their typical energy consumption during strict lockdown. This revelation emphasizes the high environmental burden of buildings, regardless of whether they are occupied.Peer ReviewedObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No ContaminantObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats SosteniblesObjectius de Desenvolupament Sostenible::12 - Producció i Consum ResponsablesPostprint (published version

Energy benchmarking of existing office stock in Spain: trends and drivers

Buildings play a central role in the clean energy transition, which is why it is vital to understand how energy is consumed in this sector. Energy performance certificate databases are considered a key source of information on the characteristics of built building stock. Despite a growing portfolio of studies based on information from such databases, little is known about energy consumption in offices. This paper explores the modelled energy performance of existing offices in Spain, using data from 13,701 energy performance certificates collected by the Catalan Institute of Energy (ICAEN) in 2013–2018. Offices were found to consume between 202.66 and 212.10 kWhp/m2·year and were mostly ranked in classes C and D (~64%). Offices with E, F or G labels represent ~28% of the sample while A and B energy ratings are very scarce (~8%). Key drivers of energy consumption variation were found to be the office type, construction period, climate zone, renewable energy use, energy certification procedure and motivation for obtaining an energy performance certificate. Ownership was not found to affect average calculated energy consumption. The results will help policy makers to plan future energy conservation strategies.Peer ReviewedPostprint (published version

Office representatives for cost-optimal energy retrofitting analysis: a novel approach using cluster analysis of energy performance certificate databases

A large number of buildings must be evaluated to formulate energy retrofitting policies for existing building stock. In this context, it is crucial to identify reference buildings that can effectively represent the entire stock, since such buildings can then be used to assess the individualized cost-effectiveness of retrofitting measures. This paper presents a novel approach for identifying and defining a set of reference buildings by applying the k-means clustering method to energy performance certificate databases. To this end, a four-step methodology has been envisaged. First, an energy performance certificate database is prepared and variables that have an impact on energy consumption are pre-selected. Selected data are then pre-processed. Next, the k-means clustering method is applied. Finally, the resulting cluster centroids are used to identify the closest energy performance certificates in the database, in other words, the representative buildings that will then be used for cost-optimal retrofitting analysis. The methodology is illustrated using the energy performance certificate database managed by the Catalan Institute of Energy (ICAEN), which includes a sample of 13,701 offices. Seven representative office blocks and offices in industrial buildings and nine representative offices in residential buildings were identified. The results establish the basis for supporting strategic decision-making for energy saving retrofit interventions in existing Spanish offices.Peer ReviewedPostprint (published version

Modelling process generated nanoparticles in industrial workplaces using reduced order models

Las nanopartículas generadas en procesos (PGNP) son nanomateriales liberados de manera inintencionada en ambientes de trabajo durante procesos de alta energía como la quema de combustibles, el corte por plasma, la soldadura, el pulido de metales o la cocción de productos cerámicos. Actualmente, no existen herramientas de avaluación de riesgos para la exposición a PGNP en ambientes industriales. Como consecuencia, no se puede evaluar la exposición de los trabajadores a este tipo de contaminantes. En este contexto, hay una necesidad de desarrollar modelos para simular las concentraciones de PGNP en espacios interiores. Debido al tamaño de las PGNP (<100 nm) su comportamiento es comparable al de las moléculas de gases ideales. Por ello, se podrían usar modelos reducidos actualmente usados para simular la concentración de CO2 en espacios interiores, para simular las concentraciones de PGNP en dichos ambientes. El objetivo de este artículo es evaluar la posibilidad de crear modelos predictivos para un espacio interior usando modelos reducidos para estimar concentraciones futuras de PGNP. Primero se define el modelo, posteriormente usando la literatura se determinarán los parámetros y finalmente, el modelo se validará usando datos obtenidos de una ubicación industrial. Este trabajo está financiando por el programa LIFE (LIFE20 ENV/ES/000187).La investigación presentada en este artículo esta financiada por el programa LIFE (LIFE20 ENV/ES/000187).Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraObjectius de Desenvolupament Sostenible::3 - Salut i BenestarPostprint (published version