bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of Thermal Bridges with an Automated Framework using BIM
Authors: Bollez M. , Klein R. , Saelens D. 
Published: December 2023

Abstract
In response to increasingly stringent energy performance requirements for buildings, the need for energy-efficient construction becomes ever more important. Although new construction technologies have emerged, thermal bridges are still common in new and especially in to-be renovated buildings. To facilitate analysing the effect of thermal bridges this paper investigates the development of a method to automatically integrate their effect into energy simulations. The developed workflow starts with integrating thermal bridges into Building Information Modeling (BIM) software. Subsequently, the thermal bridges are exported to the open source format Industry Foundation Class (IFC). Finally, a conversion of the IFC file to a readable file for the energy simulation software Modelica, using the ifc2modelica tool is shown. Furthermore, it investigates the impact of thermal bridges on different key performance indicators (KPIs) for both renovation and new build cases. This research aims at efficiently integrating thermal bridges in energy simulations during early design stages. The foundation for a BIM-library for standard thermal bridges has been developed, allowing an easy integration in existing BIM models with good simulation results.
Over- and underconsumption of residential heating: Analyzing occupant impacts on performance gaps between calculated and actual heating demand
Authors: Hansen Anders Rhiger , Gram-Hanssen Kirsten 
Published: December 2023

Abstract
Previous research estimates that building physics and occupant practices equally contribute to the explanation of variations in residential heating consumption. However, the so-called performance gap, where calculated heating demand diverge from actual heating consumption, indicates that the relation between occupant practices and building physics vary across energy efficiency of the building. In this paper, using data from 2019 to 2021, we investigate such interactions 1) by comparing the calculated heating demand with actual energy consumption for residential space heating and domestic hot water (DHW) across energy performance certificates (A to G), and 2) by investigating variations in over- and underconsumption (deviance from calculated to actual) across socio-economic characteristics of households. In line with previous studies, we find that households living in energy inefficient houses tend to have lower heating demand than expected. Moreover, we find that lower-income households and households living in rural area has less overconsumption, indicating that they have more frugal heating practices.
Airtightness of Estonian dwellings – median and base-values for heat loss estimation.
Authors: Hallik Jaanus , Kalamees Targo , Pikas Ergo 
Published: December 2023

Abstract
The field measurements of airtightness in Estonian detached houses and apartment buildings, conducted between 2003 – 2022, were combined into a large dataset for statistical analysis. The buildings (539 in total) constructed between 1810 and 2022 were classified based on dwelling type, building structure, number of storeys, year of construction, energy classification and compactness factors. The data was statistically analysed to determine the mean and median air leakage rates at 50 Pa and tested (Kruskal-Wallis test with post-hoc Conover test) for significant differences within the grouping factors. Buildings constructed after the enforcement of the compulsory Energy Performance certification have on average across all building structure types significantly lower mean air leakage rate (1.6 m3/(h·m2)) than older buildings (6.9 m3/(h·m2)), although log-wood and brick construction types feature slightly higher average air leakage rate. Previous experience with air leakage measurements help to achieve better airtightness on building site. A systematic and recurring measurement practice within a single construction company leads to significantly lower air leakage also for new concrete buildings. Detailed assessment of older buildings showed that all timber-based construction types had significantly higher air leakage rate along with higher variability compared to precast large concrete panel stone and small block wall and brick buildings. All apartment buildings built before 2010 had significantly lower air leakage rate compared to detached houses while there was no difference in new buildings. Along with the mean and median value a base value of air leakage rate q
E50,base was calculated for all construction types and age groups including 50% of measured buildings around the mean within each group with 84 % confidence interval. The calculated mean, median and base values of air leakage rate provide a way for more accurate heat loss estimation at the district-level or building-level modelling of energy saving potential of different retrofitting strategies based on building age, construction type and other building information data.
Exploring the variability of hygrothermal material properties in historic bricks in London
Authors: Xu Bingyu , Cambray Toby , Marincioni Valentina , Mavrogianni Anna 
Published: December 2023

Abstract
In the UK, a large number of traditional buildings are made of solid brick walls. If appropriate retrofit measures are taken, these buildings can contribute to achieving the UK Government’s pledge to reduce greenhouse gas emissions. The vast majority of solid brick buildings in London are non-insulated. Adding internal wall insulation is one possible energy retrofit measure, however, the insulation layer can alter the moisture balance of the wall. Since the hygrothermal properties of the existing building materials can influence the moisture balance of the wall considerably, identifying the wall type and understanding its hygrothermal properties is extremely important in building retrofit. The objective of this study is to explore the variability of the hygrothermal properties of different bricks from one wall located in London. Several brick samples are selected from one case study wall in London. The hygrothermal properties of 21 historic bricks were measured, including the absorption coefficient, bulk density, drying coefficient, water content at capillary saturation to determine the variability. The experimental results show variability of some material properties, particularly the absorption coefficient. This can potentially have significant implications for solid wall retrofit and material property characterization.
Effect of demand-controlled ventilation strategies on indoor air pollutants in a classroom: A Norwegian case study
Authors: Yang Aileen , Andersen Kamilla Heimar , Hak Claudia , Mikoviny Tomas , Wisthaler Armin , Holøs Sverre B. 
Published: December 2023

Abstract
The choice of the minimum ventilation rate (Vmin) in a demand-controlled ventilation strategy can influence energy demand but also introduce outdoor air pollutants. The latter may have direct health effects, as well as affect indoor chemical reactions. In this paper, we evaluate the effect of ventilation rates and operation hours on the level of CO2, nitrogen dioxide (NO2), and ozone (O3) in a classroom during normal use. We compared the baseline ventilation scenario (S0) with a Vmin of 430 m3/h with S1; Vmin of 150 m3/h for normal ventilation operation time (6:30-17:00) and continuous ventilation for 24h (S2). We found that S1 with reduced Vmin would lower the ozone concentration by 35% during the hours before occupancy compared to S0. Moreover, continuous ventilation during night time with a low Vmin resulted in almost as high O3 concentrations as the baseline ventilation scenario. As O3 reacts easily with certain VOCs to produce secondary organic aerosols, the level of Vmin and the ventilation duration would impact the indoor air quality upon entering the classroom.
Dynamic modeling of airflow rate through window openings based on CO2 data
Authors: Schreck Cédric , Rouchier Simon , Foucquier Aurélie , Wurtz Etienne 
Published: December 2023

Abstract
Better estimation of air change rate in naturally ventilated buildings is a key for supporting passive summer thermal comfort strategies. In window aired configurations, this estimation is challenging either with measurements or building simulation methods. In this study, we describe and apply the state space modeling methodology based on the carbon dioxide concentration (CO2) mass balance equation to a simple test case with numerically generated data. We show that a two-state CO2 / Air Change Rate model is suitable. As a modeling novelty, we demonstrate the benefit of improving the formulation with a variable diffusion term for the air change rate state equation. From the test case study findings, we emphasize that a lower interior-exterior CO2 difference results in weaker performance and we list some prospects for future work.
Potential for Electricity Reduction in Demand Response Using Building Thermal Storage
Authors: Nagai T , Tanno K , Kuboi D , Kakegawa T , Yokoyama K , Nambu H 
Published: December 2023

Abstract
Demand response (DR) contributes to filling the gap between electricity supply and demand by controlling energy resources on the consumer side and promoting the installation and use of renewable energy. This study is performed to identify the potential of building thermal storage for power reduction in DR. In addition, the optimal conditions are identified, in particular the on/off status of air-conditioning and changes in room temperature setpoints. A simulation model for an office building equipped with packaged air-conditioners is developed, and dynamic programming is applied to calculate the on/off and load ratios to minimize the cumulative electricity during the DR period. Based on the results, two types of operations are suggested: one is to maintain the temperature at the upper allowable limit (in cooling) during the DR period, and the other is to repeatedly turn the air-conditioner on and off. In addition, the following factors affect power reduction: the allowable room temperature range, the time between the request for reduction and the start of the DR period, and the partial load characteristics of the air-conditioning equipment.
Linking dataset quality and MPC in buildings: impact of temporal resolution
Authors: Erfani Arash , Jafarinejad Tohid , Roels Staf , Saelens Dirk 
Published: December 2023

Abstract
This study aims at assessing the impact of dataset quality on the performance of Model Predictive Control (MPC). The dataset feature, which is the target of this study, is temporal resolution, which applies to both data logging and the controller time step. A high temporal resolution might result in a more accurate predictive model, but it increases the need for data storage as well as the computational load on the model training. From the controller side, increasing the temporal resolution might lead to better control performance, but it sabotages the real-time response of the system. First, predictive models are developed based on datasets with different temporal resolutions. Subsequently, these predictive models are implemented within an MPC. Results reveal that decreasing the time step lower than 1 hour does not significantly improve the performance of the MPC. However, increasing the time step of MPC above 1 hour deteriorates its performance. Real-time response of the controller is a crucial criterion which deteriorates as the time step shortens. Hence, a suitable choice of temporal resolution is essential for developing a predictive model and MPC. In our case, a resolution of 1 hour is enough to guarantee a good performance of the controller.
Development of smart control system for leakage warning in compact roofs
Authors: Asphaug Silje , Geving Stig , Moschetti Roberta 
Published: December 2023

Abstract
Smart Sensor technologies to monitor temperature and moisture conditions in building components, can be used to give automatic warnings for abnormal high levels of moisture. Flat compact roofs are of particular interest, especially due to their vulnerability to rain leakages through the roofing membrane. Installing moisture sensors in such a roof measuring relative humidity (RH) or free water may give an early warning of rain leakages or condensation due to air leakages from indoors – before they start to get problematic. One challenge is, however, that normal moisture redistribution in the insulation layer over the season or day may give very high levels of RH in the top or bottom part of the insulation. The sensor system must be able to distinguish between these normal levels and leakage events. Together with a sensor technology and control system producer we have previously developed a semi-quantitative system that defines typical or normal RH levels in the insulation layer during the year. This system was based on hygrothermal simulations for various conditions, such as different exterior climate and levels of built-in moisture. This paper presents the preliminary findings from the further development of the system using real measurements from two pilot buildings located in Norway.
Experimental study of a heat recovery ventilator preheated by a Building Integrated Photovoltaic system in a cold climate
Authors: Li Jing , Ye Kai , Baril Daniel , Ge Hua , Zmeureanu Radu , Athienitis Andreas K. 
Published: December 2023

Abstract
The use of heat recovery ventilators (HRVs) in cold climate housing is becoming increasingly common, to provide outside air to the occupied space while recovering heat from the exhausted air. However, frosting of the heat exchanger core impedes HRV operation in cold climate conditions. Strategies for defrosting the core include recirculating the exhaust airstream while stopping the supply of the outside air during the defrost cycle. Preheating the air using heating coils is also used, but its application is limited by the increased energy use of the preheater. This study aims to investigate the impact of a building integrated photovoltaic/thermal (BIPV/T) system on the HRV thermal performance by using it to preheat the outside air. In this experimental study, measurements of a heat recovery ventilator preheated by the BIPV/T system are carried out in a test cell of the Future Buildings Laboratory (FBL) at Concordia University in Montreal, Canada. The results are compared to a HRV without BIPV/T preheating. The relative humidity, temperature and airflow rate of the fresh air and exhaust airstreams are monitored at the inlet and outlet of the HRV. The experiments are conducted during two weeks from January 26th, 2023 to February 08th, 2023. The change of the sensible heat recovery effectiveness ∈
sens
of the HRV, outside air outlet temperature T

2
from the HRV and outside air flow rate, ṁ1 and exhaust air flow rate ṁ4 are determined. The primary experimental results indicate that preheating the outside air by the BIPV/T system before entering the HRV can help to increase the outside air outlet temperature T

2
by up to 2.7°C at an outdoor temperature of -25 °C, and the sensible heat recovery effectiveness ∈
sens
, outside air flow rate, ṁ1 (23L/s) and exhaust air flow rate ṁ4 (43L/s) of the HRV are kept constant at the same level with preheating by BIPV/T on the HRV at -5 °C to -25 °C of outdoor temperature.
In-use conditions of air-tightening materials applied in the air gap of ventilated building envelope constructions: A parametric study for different European climates
Authors: Brozovsky J , Nocente A , Rüther P 
Published: December 2023

AbstractMaterials used in the building envelope have to withstand a wide range of varying and harsh conditions over their life cycle. Particular relevance falls upon the materials used for tightening buildings, such as wind barriers and tapes, as air infiltration was found to be responsible for between 10 and 30 % of heat losses of different national building stocks in Europe. However, there is large uncertainty about the conditions a material is exposed to over a building’s service life. A validated, hygrothermal model of a zero emission office building in Trondheim, Norway was simulated with 10-year climate files from different European locations: Bergen (NO), Berlin (DE), Oslo (NO), Paris (FR), Rome (IT), Tromsø (NO), and Trondheim (NO). This was done to investigate the temperature and humidity conditions in the ventilated air gap. The results show the total and median values for temperature in the ventilated air gaps of the simulated building’s walls and roof for the investigated locations. Moreover, the maximum change compared to the previous hour and the distribution of hours in 5 °C temperature and 10 % relative humidity intervals of the roofing underlay and wall to the west are reported.
Numerical sensitivity analysis of the energy performance of building envelope with dynamic conditions
Authors: Veit Martin , Johra Hicham , Jensen Rasmus Lund , Rask Nikolaj , Roesgaard Simon 
Published: December 2023

Abstract
The accurate energy performance assessment of building elements remains an active research topic. Studies have indicated that the thermal mass of building envelopes could influence heat losses in dynamic conditions and lead to significant difference in performance compared to steady-state conditions. This article aims to identify the relevance of using dynamic simulations instead of steady-state calculations for the energy performance assessment of building elements in Denmark. A numerical sensitivity analysis is performed on various parameters. The Monte-Carlo approach is used to perform numerous BSim simulations, which are then compared to standard steady-state calculations. The varied parameters include solar absorptance, ventilation in cavities, insulation material, insulation thickness, and orientation. Preliminary results indicate that dynamic conditions can significantly alter the wall heat losses, by up to 20% when compared to steady-state conditions. However, when aggregated, the differences average out to only 4% lower heat losses. When focusing on the thermal inertia of insulation materials, denser insulation materials only slightly delay the heat loss in the building element, but this effect is nullified over longer periods. The sensitivity analysis indicates that the most influential parameter is the solar absorptance, while the type of material is close in significance to the other parameters. The specific heat capacities and density of the insulation layer does not have a significant influence compared to its thermal conductivity. Thus, insulation materials with higher thermal mass do not seem to significantly improve the thermal performance of a building envelope.
Thermal performance of wedge pile slab foundation without frost protection insulation and highly insulated slab on ground floor – first year measurements
Authors: Lomp Siim , Kalamees Targo , Hallik Jaanus , Needo Roomelt 
Published: December 2023

Abstract
In the Nordic countries frost insulation is necessary if the foundation is above the frost-free depth. The thermal performance of the pile foundations is between a shallow ground foundation and a frost wall foundation. The pile ends extend below the frost line to help insulate the ground beneath a building’s foundation. The ends of the piles extend below the frost line to prevent the foundation of the building from frost heaving. However, there may be a risk that the ground below the slab on ground may freeze and frost heaving may occur there. The risk of frost below the slab on ground floor and/or basement increases because increasing thickness of floor insulation remarkable influences frost insulation dimensioning. In this study a 6.5 × 17-meter size uninsulated wedge pile slab foundation with highly insulated (U=0.07 W/(m2·K)) slab on ground floor was constructed for a heated building and equipped with temperature, soil moisture, relative humidity, and heat flux sensors. Seven temperature measurement piles below the building and one for reference 8 meters far from the building reached a depth of up to 3.2 meters, which is deeper than the usual 1.4 m depth to avoid freezing in foundation design. In three places, the temperature below the insulation of slab on the ground is measured at 0.5 meters step up to 3 meters from the outer wall of the building. The first-year measurement results showed that temperature did not drop below the zero degree below the foundation and floor. Even though during winter the daily average absolute minimum temperature was -24 °C the sum of degree hours below the zero degree was -7300 °Ch. The historic 50-year absolute sum of minimum degree hours below the zero degree was -28600 °Ch. In addition to real measurement results this three-dimensional temperature sensor field helps to calibrate and validate dynamic model for temperature simulation of thermal performance of wedge pile slab foundation without frost protection insulation and highly insulated slab on ground floor.
Influence of the active irrigation system on the vegetation façade
Authors: Chabada Marek , Juras Peter , Durica Pavol 
Published: December 2023

Abstract
Urban population growth has resulted in land use changes and the replacement of many vegetated areas with hard dark surfaces. The altered surfaces warm the urban climate, a phenomenon known as the urban heat island (UHI) effect. Green systems such as vegetated facades significantly affect the outdoor microclimate through evapotranspiration cooling. In particular, the method of irrigation has a major influence on evaporation efficiency. This paper investigates the effect of an active vegetated façade irrigation system on the surface temperature behaviour of the envelope. The maximum difference between the surface temperature of the actively irrigated vegetation wall and the vegetation wall irrigated by hourly interval was almost 14°C. When comparing the surface temperatures of the actively irrigated vegetated façade with the non-vegetated façade - dark cladding, the maximum difference was almost 15°C. The difference between the surface temperature of the actively irrigated vegetated façade and the surface temperature behind the air cavity was almost 9°C. This reduction in temperature results in a shading effect of the vegetation wall. The use of vegetated structures is proving to be an effective tool and mitigation of temperatures in urban environments.
Heat loss characteristics of typology-based apartment building external walls for a digital twin-based renovation strategy tool
Authors: Iliste Elisa , Lomp Siim , Pikas Ergo , Arumägi Endrik , Hallik Jaanus , Õiger Karl , Kisel EInari , Liiv Innar , Kalamees Targo 
Published: December 2023

Abstract
Information about existing building structures is necessary for creating a renovation strategy. Older buildings are often built using typical building envelope structures. However, this information is presented in the building register at a general level, specifying the material type but not its characteristics. For a cross-regional reconstruction strategy, it is necessary to link the scarce information in the building register with the heat loss characteristics of the building envelope structures. In the current study, we classified external wall solutions according to building typologies and linked this with building register information. The typology database includes log, timber frame, brick, concrete, and aerated lightweight concrete external wall structures. Comparing the typology-based values and the actual situation showed that the wall structures’ expected and actual heat loss characteristics agreed. However, there were also significant deviations, primarily because the data from the building register did not allow for precise classification. Nevertheless, data showed that building typology-based heat loss properties are necessary for developing a district-based renovation strategy.