Low-energy Residential Buildings Research Articles

Influence of Temporal- and Spatial Resolutions on Building Performance Simulation Models: A Danish Residential Building Case Study

This study aims to assess the accuracy of a building performance simulation (BPS) model developed in IDA ICE software, focusing on heating energy use and indoor air temperatures in a low-energy multi-story residential building located in Northern Denmark. Six apartments were analyzed, and a comparative analysis was conducted between the measured parameters and the results obtained from BPS models with different spatial and temporal resolutions. The findings indicate that while the BPS models can provide reasonably accurate estimates of heating energy use, they may not fully capture the nuanced response to factors such as indoor air temperature This highlights the importance of incorporating qualitative inputs and environmental variables into these BPS models, including heating and/or cooling setpoints, internal gains, and weather conditions. Overall, this study provides insights into the limitations and opportunities of BPS models for accurately estimating heating energy use and indoor air temperatures in low-energy residential buildings.

Comparison of the embodied and operating energy in agricultural greenhouses and in residential buildings

The increase of the energy efficiency in buildings and greenhouses is important for reducing the use of fossil fuels and the emissions of greenhouse gases. Energy efficiency evaluation requires the consideration of both the embodied and the operational energy. Many estimations regarding the embodied and the operational energy in various types of buildings have been reported so far. However, studies regarding the embodied energy in agricultural greenhouses are rare while there are many estimations regarding their operational energy. The goal of our study is the comparison of the embodied and the operational energy in residential buildings and in agricultural greenhouses. The embodied and operational energies are compared in greenhouses as well as in low-energy and in conventional residential buildings.  Our results indicate that the ratio of embodied energy to life-cycle energy in low-energy residential buildings and in nearly-zero energy buildings varies in the range at 36% to 83% that is significantly higher than the ratio in conventional residential buildings which is in the range of 6% to 20%. The ratio of embodied energy to life-cycle energy in agricultural greenhouses, at 0.86% - 70.41%, varies significantly depending on many parameters. The importance of carbon emissions related to embodied energy in low-energy buildings, in net-zero energy buildings and in agricultural greenhouses is highlighted.  Our work could be useful to policy makers who are willing to accelerate the green transition to a low carbon economy in the coming decades.

On the effectiveness of passive controls for summer thermal comfort in highly insulated dwellings

ABSTRACT Among environmental controls, solar shading and ventilative cooling are widely considered as key passive strategies for limiting the overheating risks in buildings. While their application is encouraged through Energy Performance of Buildings Directive regulations, several studies have shown that summer thermal comfort in heating-dominate temperate climates still requires deeper investigation, particularly in low-energy residential buildings. Based on qualitative and quantitative data collected through surveys and monitoring in 147 highly insulated houses in Wallonia (Belgium), this paper gives an overview of the implemented passive strategies and discusses their effectiveness. Statistical tests are conducted to evaluate their impact on both perceived and measured indoor conditions. In general, the results highlight a limited impact of the implemented strategies, questioning their proper operation. Operational modes for environmental controls thus appear crucial, and should better respond to occupants’ needs, preferences and control opportunities. At a more general level, the study calls for a better understanding of the barriers inhibiting successful integration and operation of environmental controls, in order to effectively reduce overheating risks in residential buildings and limit future diffusion of active cooling systems with their induced environmental impacts.

Low-energy residential building optimisation for energy and comfort enhancement in semi-arid climate conditions

The application of energy-efficient strategies in buildings, such as the Green Building Concept, can significantly impact human comfort and resource consumption. However, due to the complexity of decision-making factors and the variety of available materials, computational models are necessary to identify the most effective solutions and optimise building energy performance. This study presents an integrated framework that uses machine learning algorithms and a Petri Net control system to optimise the thermal, comfort, and energy efficiency of both vertical and horizontal building envelopes in semi-arid climate zones. The framework incorporates several passive techniques for building energy parameters, including material thickness and melting point, window types, wall insulation thickness and thermal emissivity, wall solar absorbance, window wall ratio, fenestration position, air tightness, roof solar reflectance, roof insulation thickness and conductivity (W/(m·°C)), and floor insulation thickness. An experiment design was developed using Box-Behnken Design-Response Surface Methodology (BBD-RSM) for statistical optimisation, which was coupled with Design Builder simulation model. The methodology was demonstrated by applying it to a residential building in Mexico. Meta Additive Regression was used to analyse the output factors, which showed higher confidence compared to REP Tree and M5P Tree algorithms in green buildings. The results demonstrate that an annual energy reduction of 50 kW/m2 per household can be achieved by using an optimised building envelope.

Durability of humidity-based ventilation components after 13 years of operation in French residential buildings – Assessment of components performance in laboratory

Humidity-based DCV systems have been widely used in France for 35 years and are considered as a reference system, including for low-energy residential buildings. The on-going “Performance 2” project delivers feedback from 13 years of on-site operation in twenty-two social housing apartments. The initial project was a large-scale monitoring on thirty new occupied apartments in two buildings in France equipped with this DCV system, which extended from 2007 to 2009. Thirteen years later the buildings are re-visited, and the monitoring system is turned back on with the intention to assess the ventilation system performance after a prolonged in-situ functioning period. Then, the components have been collected and tested in laboratory facilities: as collected, after cleaning, and finally after a light rehabilitation. Despite largely insufficient levels of maintenance, 100 % of the exhaust units and air inlets not purposely degraded by the occupant, still reacted as expected to humidity. A good relationship was found between the visual maintenance level and the limitation of maximum airflow for each Air Terminal Device (ATD): an average limitation of −10.6 m3/h has been evaluated for ATDs presenting a “Bad” level of maintenance whereas the average limitation was only −2.2 m3/h for ATDs showing a “Good” maintenance state. Finally, after cleaning and refurbishing, but without touching the hygroscopic sensor/actuator, the ATDs still meet the specifications and are very close to their original characteristics.

Effect of the envelope structure on the indoor thermal environment of low-energy residential building in humid subtropical climate: In case of brick–timber vernacular dwelling in China

The brick–timber structure plays a crucial role in creating a comfort indoor thermal environment for low-energy vernacular dwellings. Herein, the thermal environment of the dwelling was studied by DesignBuilder software and evaluated using Adaptive Predicted Mean Vote (APMV) index. These results revealed that the indoor damp and cold feelings intensified in winter, and the mountain as a natural wind barrier weakened the attack of the prevailing wind in winter. These results leaded that the wind speed of the tested room was lower than 0.1 m/s. The thermal comfort satisfactory days in a year accounts for 56.2%, and the overall level of indoor thermal environment was low in the rest of the year, especially in winter. The simple structure of the exterior envelope and the single material were the main reasons for the poor indoor thermal environment of naturally ventilated buildings. Therefore, optimization strategies such as increasing the insulation materials of the envelope and adopting insulating glass windows were proposed. Compared to that before the retrofitting, the overall thermal environment grade of the vernacular dwelling has been improved by 4.7% (grade I), -0.3% (grade II) and -4.3% (grade III), respectively. The poor thermal performance and airtightness of the envelope easily lead to the negative effect of outdoor cold, heat and water vapor entering the house, which affects the thermal environment grade. These conclusions provided a reference for the optimization of the thermal environment of existing low-energy vernacular dwellings in subtropical humid climate areas. • Poor indoor thermal environment in winter in low-energy buildings. • Building airtightness is as important as the thermal performance of the envelope. • Buildings in humid subtropical climates should be well protected from moisture. • The height of surrounding buildings influences wind speed and shading

Energy, comfort, and environmental assessment of passive techniques integrated into low-energy residential buildings in semi-arid climate

Residential buildings consume a lot of energy, particularly after the recent pandemic and remote working lifestyle. Thus, it is crucial to design energy-efficient buildings that reduce energy consumption without losing indoor thermal comfort. In this regard, integrating affordable passive strategies can improve thermal comfort, energy efficiency, and other environmental setbacks. In this study, several passive techniques were parametrically analyzed and tested in real semi-arid conditions using building simulation tools. The analyzed passive strategies include a phase change material (PCM), reflective paint, insulation, double-clear glazing, double low-E glazing, reflective glazing, and shading. Three of Monterrey’s major energy-consuming typical houses were analyzed, and the optimum configuration was selected based on annual energy saving and initial material cost-effectiveness. Although the PCM was thermally effective when integrated into walls and roofs, as well as in terms of total energy reduction, the results showed that it was not cost effective. Therefore, insulation and reflective paint in walls and roofs were applied in conjunction with low-E glazing and shading in all cases to save more than 50% of energy annually. The use of these energy-saving techniques increased the hours of comfort by up to 45%, resulting in a reduction of up to 3000 kgCO2e.

Hourly Simulation of an Earth-to-Air Heat Exchanger in a Low-Energy Residential Building

The earth-to-air heat exchanger (EAHE) is a well-founded and verified solution used in modern buildings both for heating and cooling purposes around the world. However, there is a lack of studies on operation of such devices cooperating with ventilation systems of buildings in hourly time step. In this study, the 5R1C thermal network model of a building from EN ISO 13790 was coupled with the EAHE model from EN 16798-5-1 to calculate hourly outlet air temperature. To improve the effectiveness of the considered solution, an additional algorithm was developed to choose between the EAHE outlet and ambient air as the source of ventilation air. Simulations were conducted in a spreadsheet for a low-energy single-family building. Ground temperature was compared with measurements taken in the considered location. The application of the EAHE with the proposed bypass resulted in a decrease in annual energy use for space heating and cooling from 14.82 GJ and 1.67 GJ to 12.74 GJ and 0.93 GJ, i.e., by 14% and 44%, respectively. Peak hourly heating and cooling thermal power decreased from 2.73 kW and 3.06 kW to 2.21 kW and 2.34 kW. Introduction of a bypass and switching between the EAHE and ambient air as the source of ventilation for the building resulted in annual energy savings of 123 kWh.

Design parametric analysis of low-energy residential buildings on the way to a defined cost-optimal capacity point

One of the most energy-saving design aspects is the reliability of the envelopes, which helps to monitor the temperature of the building and thus reduces dependence on mechanical heating, ventilation, and air conditioning systems for heating or cooling the building. This study designs home retrofits and new construction of single-family buildings by assessing parametric sweeps, building design, and cost-based energy savings building analysis. The goal of this research is to determine the most cost-effective paths for a single-family building. For building design, we chose nine capacity points with the lowest cost. BEopt offers comprehensive building-based assessments, including scale, occupancy, design, location, vintage, and utility prices. Equipment and discrete envelope options that reflect realistic building practices and materials are evaluated. The impact of carbon emission reductions is calculated on an annual basis. The proposed building's energy savings are calculated concerning a B10 benchmark. The parametric analysis results were compared to the B10 Benchmark, and the proposed building energy consumption of Point 4 (12.4%), Point 6 (13%), Point 8 (7.4%), and Point 9 (8.2%) was lower than the B10 Benchmark. Point 6 is our proposed design's most cost-effective capacity point. Our proposed method allows us to analyze residential building structures and define cost-optimal performance packages at different energy consumption rates in all single-family buildings. Users can specify options to be considered in the optimization by selecting predefined options from various categories.

A Lifecycle Assessment of a Low-Energy Mass-Timber Building and Mainstream Concrete Alternative in Central Chile

While high-rise mass-timber construction is booming worldwide as a more sustainable alternative to mainstream cement and steel, in South America, there are still many gaps to overcome regarding sourcing, design, and environmental performance. The aim of this study was to assess the carbon emission footprint of using mass-timber products to build a mid-rise low-energy residential building in central Chile (CCL). The design presented at a solar decathlon contest in Santiago was assessed through lifecycle analysis (LCA) and compared to an equivalent mainstream concrete building. Greenhouse gas emissions, expressed as global warming potential (GWP), from cradle-to-usage over a 50-year life span, were lower for the timber design, with 131 kg CO2 eq/m2 of floor area (compared to 353 kg CO2 eq/m2) and a biogenic carbon storage of 447 tons of CO2 eq/m2 based on sustainable forestry practices. From cradle-to-construction, the embodied emissions of the mass-timber building were 42% lower (101 kg CO2 eq/m2) than those of the equivalent concrete building (167 kg CO2 eq/m2). The embodied energy of the mass-timber building was 37% higher than that of its equivalent concrete building and its envelope design helped reduce space-conditioning emissions by as much as 83%, from 187 kg CO2 eq/m2 as estimated for the equivalent concrete building to 31 kg CO2 eq/m2 50-yr. Overall, provided that further efforts are made to address residual energy end-uses and end-of-life waste management options, the use of mass-timber products offers a promising potential in CCL for delivering zero carbon residential multistory buildings.

An Overview: PM2.5 Concentration Levels in Urban Residential Buildings during the Past Two Decades

The public has become increasingly aware of the critical effect of fine particle matter (PM2.5) on indoor air quality. Urban residents spend more than half of their time at home. Therefore, monitoring PM2.5 concentrations in residential settings is critical. This paper presents a review of studies on PM2.5 concentrations in the living rooms of urban residential buildings. We included studies measuring indoor PM2.5 concentrations across different regions worldwide and then summarized the measured concentrations. Factors contributing to differences in indoor concentrations were identified and explained. The review results revealed that most of the included studies were conducted in Asia and in Europe, and some were conducted in North America and Africa. Moreover, the mean daily PM2.5 concentration ranged from 17.3 µg m-3 in North America to 68.6 µg m-3 in Asia. Factors influencing PM2.5 concentrations were as follows: indoor activities, ventilation type and air cleaner (AC) use, building type and performance, ambient environment and season. Smoking and cooking considerably increased PM2.5 concentrations in the living rooms, even in measurements conducted over a short time. The use of an AC could reduce indoor PM2.5 concentration in an average of 60%. Regarding building type, PM2.5 concentration in multifamily apartment buildings had higher PM2.5 concentrations than did single-room residences. Moreover, severe outdoor particle pollution increased indoor PM2.5 concentrations by up to 142% in low-energy residential buildings.

An all-in-one machine coupled with a horizontal ground heat exchanger for the air-conditioning of a residential building

Heating, ventilation and air conditioning (HVAC) systems are considered of great importance in the building sector, as they represent a significant part of the energy demand in buildings. Moreover, they are deeply related to indoor environmental quality, which strongly affects occupants' quality of life. This paper presents the analysis of a compact all-in-one and plug-and-play machine providing heating, cooling and controlled mechanical ventilation to a low energy residential building. In particular, the system is composed of an air-to-air heat pump coupled to a heat recovery unit which can pre-heat the fresh air and contribute to domestic hot water production. In the present work, an additional heat exchanger embedded in the building's foundations has been included in the system to pre-heat or pre-cool the outdoor air before it enters the heat recovery unit. The compact energy system has been mathematically modelled, and its operations have been monitored in a real residential building recently constructed in Udine (North-East of Italy). The annual energy performance of the all-in-one machine has been obtained, and the system layouts with and without ground heat exchangers have been compared. The use of the ground heat exchanger helps to decrease the primary energy consumption and the operating costs (in heating, 14% and 11% respectively), improving, at the same time, the thermal comfort conditions inside the building.

IEA EBC Annex 68 – Consequences on ventilation and hygrothermal operation of buildings

The objective of the IEA EBC Annex 68 Project, “Indoor Air Quality Design and Control in Low Energy Residential Buildings”, has been to develop the fundamental basis for optimal design and control strategies for good Indoor Air Quality (IAQ) in highly energy efficient residential buildings. Focus has been on emission of chemical pollutants from building products and use of ventilation to alleviate IAQ effects. The question has been whether new paradigms for demand control should be developed based on knowledge from this project.The paper gives an overview of the project’s activities with regards to: - Gathering of laboratory and field data on pollution sources in buildings. - Formulation of a so-called “similarity approach” to predict emissions of volatile organic compounds based on knowledge from moisture transfer properties. - Gathering of a set of contemporary models to simulate the combined heat, air, moisture and pollution conditions of buildings and their assemblies. Based on this background, the project has identified and described an extended set of amenable ways to optimize the provision of ventilation and air-conditioning and to assess possibilities to bring this knowledge into practice. The paper gives an overview of the suggested solutions and their conditions.

Control strategies of solar heating systems coupled with seasonal thermal energy storage in self-sufficient buildings

A numerical analysis is carried out to investigate the influence of different solar collector control strategies on the performance of a solar heating system coupled with seasonal thermal energy storage. The system is used for space heating and domestic hot water production in a low-energy residential building. The performance of the controller is measured in terms of the minimum storage volume required to achieve an annual solar fraction of 100%. Three controllers were numerically investigated: (1) a high-flow controller (HFC) with a constant nominal flow rate of 40 l/h⋅m2, (2) a low-flow controller (LFC) with a constant nominal flow rate of 12.5 l/h⋅m2, and (3) a variable-flow controller (VFC) with a flow rate in the range 4 – 40 l/h⋅m2 whose objective function is given by a predefined temperature at the outlet of the collector. The performance of the investigated controllers is assessed by conducting full year simulations using an in-house, experimentally validated model. A detailed comparative analysis reveals that the reasons behind the specific performance characteristics of each controller are closely related to the thermal stratification effected in the storage and to the capability of the controller to preserve the stratification throughout the year.

Multi-objective optimization of building design for life cycle cost and CO2 emissions: A case study of a low-energy residential building in a severe cold climate

Multi-objective optimization of building design for life cycle cost and CO2 emissions: A case study of a low-energy residential building in a severe cold climate

Construction of green housing design methods for ancient villages in southwest minority areas

In order to actively cope with the upgrading of global climate change, through the analysis and research on the key technologies of low energy consumption of green residential buildings in ancient villages of ethnic minorities in Southwest China, this paper expounds the key technology of low energy consumption housing design in traditional villages. From five aspects of “safety and durability, health and comfort, life convenience, resource conservation, environment livability”, the new edition of “green building evaluation system” is interpreted in detail. Based on the overall analysis of the ecological technology strategy of Chinese traditional villages, this paper puts forward some feasible design optimization strategies and measures with low energy consumption green technology for the short board of traditional houses. Finally, combined with the characteristics of traditional village residential buildings, the paper puts forward a green evaluation method combining qualitative and quantitative design elements of low-energy residential buildings. Combined with the current situation of ecological environment in China, a new design method of low energy consumption housing in traditional Chinese villages is developed by combining the characteristics of traditional wisdom and key technologies of green building. This paper introduces the feasibility of the method system, and provides reference for other ancient villages in the construction of new houses in the future.

Performance and feasibility study of solar-air source pump systems for low-energy residential buildings in Alpine regions

To promote the application of renewable energy in low-energy buildings in Alpine regions, a solar-air source heat pump (SASHP) system was investigated based on a low-energy residential building in Xining City. First, a solar fresh air (SFA) heating system simulation model was established in TRNSYS software, and the reliability of the model was verified with measured values. In addition, based on the SFA heating system model, a SASHP system model was further realized. The operating characteristics of the SASHP system were explored in depth and compared with those of the single-ASHP system in the heating season. The results show that the SFA heating system model is reliable, with relative errors that can be controlled within 15%. The indoor average temperature (Tave) can be maintained from 16.13 to 19.61 °C. The SASHP system can leads to Tave fluctuations within the range of 21.4–22.9 °C, and the solar fraction can reach 55% in the heating season. Furthermore, the SASHP system can reduce energy consumption by 55.38% compared to the ASHP system; additionally, the COP of the SASHP system is 109.43% higher than that of the ASHP system, and the annual cost is 9.7% lower. Moreover, the SASHP system produces 55.48% less carbon emissions than the ASHP system. These results provide guidance for the application of SASHP systems in Alpine regions.

Exploring the localization process of low energy residential buildings: A case study of Korean passive houses

Global climate change and increasing carbon emissions from building energy use have increased worldwide attention to low energy buildings with reduced environmental impact. This study examines one type of low energy building in Korea, called the Korean Passive House (KPH), focusing on its adaptations to the local construction market and culture. To assess the efficiency of KPHs and further promote the expansion of passive houses outside their place of origin in Europe, the study investigated KPHs using three sources: archival research analyzing available government policy and regulations, case studies of 20 certified KPHs on architectural design practice, and energy simulation analyses comparing conventional and KPH energy uses. Results show that the KPHs have customized their practices to meet various needs emerging from the distinctive local context. Overheating problems caused by ondol, a traditional water-based underfloor heating system, are prevented by adjusting the U-values of the prototype envelope. The KPHs typically use local materials, products, and technologies already available in the Korean construction market to reduce embodied energy and achieve intended efficiency. We suggest that future research be conducted to reflect user behavior and satisfaction and perspectives of professionals since they are directly or indirectly influenced by building energy consumption.

Evaluation of energy flexibility of low-energy residential buildings connected to district heating

Energy flexibility is a cost-effective solution to facilitate secure operation of the energy system while integrating large share of renewables. Thermal energy infrastructure is a great asset for flexibility in systems with widely developed district heating networks. The aim of the present work is to investigate the potential for low-energy residential buildings to be operated flexibly, according to the needs of district heating system. An apartment block is studied, utilizing the storage capacity of thermal mass as storage medium. Two sets of data are utilized: heat load of Greater Copenhagen and dynamic heat production cost which is used as a price signal for the scheduling of the heating use in the building. Scenarios with different control signals are determined in order to achieve load shifting. The findings show that pre-heating is highly effective for load shifting and peak load reduction. During morning peak load hours, energy use is reduced in all scenarios between 40% and 87%. Although with load shifting higher energy use may occur, it occurs mostly at times when the city heat load is lower and heat production is less expensive and less carbon-intensive. Indoor temperature has a wider range and/or more fluctuations, yet remains within acceptable limits.

Models for residential indoor pollution loads due to material emissions under dynamic temperature and humidity conditions

The IEA EBC Annex 68 project on “Indoor Air Quality Design and Control in Low Energy Residential Buildings” has been recently completed. The project considered indoor air pollution loads in dwellings, particularly how such pollutants are emitted in dependency of the hygrothermal conditions: temperature, moisture and air flows. Thus, a proper understanding of the mutual interactions between hygrothermal conditions and pollutants was needed to obtain optimal paradigms for demand-controlled ventilation. The project adopted a similarity approach for modelling the transports of moisture and volatile organic compounds (VOCs) in materials, and thereby it was possible to provide a comprehensive set of data and tools whereby the indoor atmospheric conditions of buildings can be optimized, e.g. with respect to the need for ventilation. The paper explains the experimental and modelling approach and presents a summary of the results.