• Energy Research

Abstract In Portugal, there is a lack of quantitative studies on the thermal performance of earthen buildings. This paper aims at contributing to this research context by studying site-specific strategies, and the thermal performance and comfort conditions of a rammed earth building located in southern Portugal. The study is based on objective and subjective assessments and consists of assessing the hygrothermal conditions, thermal comfort levels and analysing the occupants' perception regarding thermal sensation. The results showed that the strategies used are closely related to local conditions, mitigating the effects of high summer temperatures and ensuring a good summer thermal performance by passive means alone. During the summer monitoring, results showed that the building stayed most of the time (80%) in Category I (high level of expectation) and the remaining time in Category II, according to the classification method defined by the standard EN15251. During the winter period, the building had the worst performance, being necessary a heating system to guarantee comfort conditions. Additionally, the results showed that the good thermal performance of the case study depended more on the high thermal inertia than on the U-value of the envelope. Limitations and advantages of the use of earthen construction elements are discussed.

Abstract In Portugal, there is a lack of quantitative studies on the thermal performance of earthen buildings. This paper aims at contributing to this research context by studying site-specific strategies, and the thermal performance and comfort conditions of a rammed earth building located in southern Portugal. The study is based on objective and subjective assessments and consists of assessing the hygrothermal conditions, thermal comfort levels and analysing the occupants' perception regarding thermal sensation. The results showed that the strategies used are closely related to local conditions, mitigating the effects of high summer temperatures and ensuring a good summer thermal performance by passive means alone. During the summer monitoring, results showed that the building stayed most of the time (80%) in Category I (high level of expectation) and the remaining time in Category II, according to the classification method defined by the standard EN15251. During the winter period, the building had the worst performance, being necessary a heating system to guarantee comfort conditions. Additionally, the results showed that the good thermal performance of the case study depended more on the high thermal inertia than on the U-value of the envelope. Limitations and advantages of the use of earthen construction elements are discussed.

Abstract The improvement of the use of renewable energy sources, such as solar thermal energy, and the reduction of energy demand during the several stages of buildings' life cycle is crucial towards a more sustainable built environment. This paper presents an overview of the main features of lightweight steel-framed (LSF) construction with cold-formed elements from the point of view of life cycle energy consumption. The main LSF systems are described and some strategies for reducing thermal bridges and for improving the thermal resistance of LSF envelope elements are presented. Several passive strategies for increasing the thermal storage capacity of LSF solutions are discussed and particular attention is devoted to the incorporation of phase change materials (PCMs). These materials can be used to improve indoor thermal comfort, to reduce the energy demand for air-conditioning and to take advantage of solar thermal energy. The importance of reliable dynamic and holistic simulation methodologies to assess the energy demand for heating and cooling during the operational phase of LSF buildings is also discussed. Finally, the life cycle assessment (LCA) and the environmental performance of LSF construction are reviewed to discuss the main contribution of this kind of construction towards more sustainable buildings.

Abstract The improvement of the use of renewable energy sources, such as solar thermal energy, and the reduction of energy demand during the several stages of buildings' life cycle is crucial towards a more sustainable built environment. This paper presents an overview of the main features of lightweight steel-framed (LSF) construction with cold-formed elements from the point of view of life cycle energy consumption. The main LSF systems are described and some strategies for reducing thermal bridges and for improving the thermal resistance of LSF envelope elements are presented. Several passive strategies for increasing the thermal storage capacity of LSF solutions are discussed and particular attention is devoted to the incorporation of phase change materials (PCMs). These materials can be used to improve indoor thermal comfort, to reduce the energy demand for air-conditioning and to take advantage of solar thermal energy. The importance of reliable dynamic and holistic simulation methodologies to assess the energy demand for heating and cooling during the operational phase of LSF buildings is also discussed. Finally, the life cycle assessment (LCA) and the environmental performance of LSF construction are reviewed to discuss the main contribution of this kind of construction towards more sustainable buildings.

Abstract In this paper a new numerical tool to estimate the operational energy of buildings, in early design stages, is presented. This tool is part of a novel approach for life-cycle analysis based on macro-components developed in the European research project SB_Steel – Sustainable Buildings in Steel . Two early design stages are considered in the scope of the methodology: the concept stage and the preliminary stage. This numerical tool enables to estimate the energy use for space heating, space cooling and domestic hot water production, taking into account (i) the climate; (ii) the use type of the building (e.g. residential, offices and commercial/industrial); (iii) the building envelope characteristics; and (iv) the building services. The developed algorithm is based on a monthly quasi-steady-state approach, modified for improved accuracy through the calibration of correction factors that depend on the climatic region and the type of building. Good results were achieved, with errors lower than 10% when compared to performance-based approaches such as the use of advanced dynamic methods. Finally, the case study of a low-rise residential building is presented, in which the results obtained from the simplified methodology are compared with the results from the simulation program EnergyPlus , showing a good agreement between them.

Abstract In this paper a new numerical tool to estimate the operational energy of buildings, in early design stages, is presented. This tool is part of a novel approach for life-cycle analysis based on macro-components developed in the European research project SB_Steel – Sustainable Buildings in Steel . Two early design stages are considered in the scope of the methodology: the concept stage and the preliminary stage. This numerical tool enables to estimate the energy use for space heating, space cooling and domestic hot water production, taking into account (i) the climate; (ii) the use type of the building (e.g. residential, offices and commercial/industrial); (iii) the building envelope characteristics; and (iv) the building services. The developed algorithm is based on a monthly quasi-steady-state approach, modified for improved accuracy through the calibration of correction factors that depend on the climatic region and the type of building. Good results were achieved, with errors lower than 10% when compared to performance-based approaches such as the use of advanced dynamic methods. Finally, the case study of a low-rise residential building is presented, in which the results obtained from the simplified methodology are compared with the results from the simulation program EnergyPlus , showing a good agreement between them.

The palafitic timber constructions of the central Portuguese coastline are an example of the adaptation to site-specific conditions (climate and sand landscape morphodynamics) using the available endogenous resources. Thus, in a context of environmental awareness and climate change, it is relevant to understand their features/strategies and how they perform. This work analyses the energy performance and thermal condition evaluation of a vernacular timber building–palheiro–from Praia de Mira, through in situ measurements, subjective analysis and energy simulation provided by DesignBuilder/EnergyPlus. The results show a good or satisfactory thermal performance during most of the seasons by passive means only. Despite, it was not possible to guarantee thermal comfort conditions for the occupants during winter. In the energy performance analysis, five scenarios, with different external walls, were compared. In the two scenarios that satisfy the maximum U-value for the climate zone, the current conventional building had a slightly better performance on heating and cooling (less 1.1 and 1.4 kWh/m2, respectively) than the timber building. However, the difference between the two construction solutions is not substantial in the annual energy demand (2.5 kWh/m2, 7.3%), indicating that timber structures are suitable in this mild climate area.