This work is focused on the identification of the energy and economic optimal thermal insulation solutions of opaque elements of the envelope of buildings located in Portugal. Five different ...buildings were selected: an apartment, a detached house, a private clinic, a private high school and a medium-sized supermarket. These buildings were supposedly located in three locations, which together represent all climatic possibilities of Portuguese temperate climate. The most common types of thermal insulation were tested, for which three alternative positions within the building envelope(inside, middle, outside) were considered. Thermal insulation thicknesses between 0 (without insulation) and 12 cm were tested.
The optimal solution depends on perspective adopted: energy or economic. In terms of cost, the EPS presents the most promising thermal insulation material and its best location is in the middle of the building envelope. Depending on the climatic zone and the buildings’ typology, the cost-optimally thickness varies between 0 and 10 cm and the better energy thickness varies from 0 to above 12 cm. Regions with more intense climate require higher thermal insulation thicknesses. Residential buildings require higher insulation thickness than the others. Buildings with permanent occupation require higher insulation thicknesses than the ones with intermittent use.
•Energy and economic optimal thermal insulation of Portuguese buildings envelope.•The building stock is represented by 5 buildings of 4 types of use.•All climatic possibilities of the Portuguese Mediterranean climate were considered.•The optimal solution obtained depends on the perspective (energy or economic).•Thermal insulation thicknesses between 0 (no insulation) and 12 cm were tested.
Despite efforts to mitigate climate change, annual greenhouse gas emissions continue to rise, which may lead to the global warming of our planet. Buildings’ thermal energy needs are inherently linked ...to climate conditions. Consequently, it is crucial to evaluate how climate change affects these energy demands. Despite extensive analysis, a comprehensive assessment involving a diverse range of building types has not been consistently conducted. The primary objective of this research is to perform a coherent evaluation of the influence of climate changes, construction element properties, and the Heating, Ventilation, and Air Conditioning (HVAC) system type of control on the energy requirements of six buildings (residential, services, and commercial). The buildings are considered to be located in a temperate Mediterranean climate. Our focus is on the year 2070, considering three distinct climatic scenarios: (i) maintaining the current climate without further changes, (ii) moderate climate changes, and (iii) extreme climate changes. The buildings are distributed across three different locations, each characterized by unique climatic conditions. Buildings’ envelope features a traditional External Thermal Insulation Composite System (ETICS) and expanded polystyrene (EPS) serves as thermal insulation material. Two critical design factors are explored: EPS thickness ranging from 0 (no insulation) to 12 cm; and horizontal external fixed shading elements varying lengths from 0 (absence) to 150 cm. Six alternative setpoint ranges are assessed for the HVAC system control: three based on the Predicted Mean Vote (PMV) and three based on indoor air temperature (Tair). Results were obtained with a validated in-home software tool. They show that, even under extreme climate conditions, the application of thermal insulation remains energetically favorable; however, its relative importance diminishes as climate severity increases. Then, proper insulation design remains important for energy efficiency. The use of external shading elements for glazing (e.g., overhangs, louvers) proves beneficial in specific cases. As climate changes intensify, the significance of shading elements grows. Thus, strategic placement and design are necessary for good results. The HVAC system’s energy consumption depends on the level of thermal comfort requirements, on the climate characteristics, and on the building’s type of use. As climate change severity intensifies, energy demands for cooling increase, whereas energy needs for heating decrease. However, it is essential to recognize that the impact of climate changes on HVAC system energy consumption significantly depends on the type of building.
Glazed systems in buildings can account for a significant part of overall energy consumption. The unfavorable relationship between energy savings and the increased cost of energy-efficient windows is ...often the main drawback cited by customers to justify its non-acquisition. of glazed windows. This study addresses the relationship between the investment costs in windows and their energy performance and associated costs. Seventeen window manufacturers were contacted. This survey studied the state-of-the-art and the most-used windows in terms of energy efficiency and cost. Calumen and Guardian Configurator software were used to perform this assessment. Additionally, SEnergEd software was used to simulate the energy performance and compute the equivalent annual cost for the entire life cycle of buildings. Besides the economic benefits, the impact of the energy performance of the windows on the energy performance of the building was also studied. In terms of energy, the most efficient glazing system was two windows per span, resulting in a combined solar factor of 0.43 and a 0.55 W/(m2·K) heat-transfer coefficient. On the other hand, one window per span, with a solar factor of 0.79 and a 3.05 W/(m2 K) heat-transfer coefficient is the most cost-efficient to be used in Portugal.
The aim of this work is to investigate the relationship between evaporation from heated water surfaces and mean aero thermal properties of a forced airflow. Flows with Reynolds numbers varying ...between 2475 and 49,503 were considered. Both wind tunnel measurements and numerical simulations were used. The experimental results were obtained in an installation consisting of a low speed wind tunnel and an evaporation tank. The numerical study was performed through a 3D-CFD code. To validate the numerical formulation the predicted results were compared with the experimental measurements for the mass transfer at the free surface of the water tank and with correlations available in the literature. A good agreement was achieved which indicates an interesting capacity of the CFD program to predict the phenomena engaged.
The dependence of the rate of evaporation with air velocity, water–air temperature difference and relative humidity is also addressed. The results obtained with both methodologies clearly show that the rate of evaporation is mainly dependent of the airflow velocity. The water–air temperature difference and the relative humidity also have an important effect, but much less than the airflow velocity. For small airflow velocities the rate of water evaporation is also small and presents only a slightly dependence from the temperature difference and the relative humidity.
•Water evaporation is related with airflow characteristics and air–water temperature difference.•Experimental results obtained in an installation consisting of a low speed wind tunnel and an evaporation tank.•3D-CFD simulation of turbulent flow with coupled heat and mass transfer at a free water surface.•Through a regression analysis of the results some new empirical correlations are introduced for the water evaporation rate.
The main goal of this research is to assess the thermal comfort quality in residential and non-residential buildings, and its relationship with the corresponding energy and economic costs, the ...building type of use, the severity of the climate, the thermal insulation of opaque elements, the type of control of the Heating, Ventilation and Air Conditioning (HVAC) system and the probable evolution of the energy price. In addition, the financial framework of the building's holder, an aspect with a huge impact on the economic cost of thermal comfort and repeatedly neglected in the literature, is considered together with all relevant parameters related with previous issues. Data were obtained with a validated in-home software. The results demonstrate that better quality of thermal comfort, with lower costs, is achieved through control of the HVAC system with Predicted Mean Vote (PMV) setpoints rather than the traditional control with air temperature (Tair); moreover, the useful thermal energy needs for climatization is substantially higher for buildings with permanent occupation than for those with intermittent use. A significant portion of the thermal comfort cost is related to the investment in the HVAC system, varying between about 20% and 70%. The rise of thermal comfort cost with the increase of the energy price inflation rate is substantially higher in the case of residential buildings. If that inflation rate is high, it will lead to an increase of families in energy poverty.
•All factors with impact on thermal comfort quality, energy and cost were considered.•The influence of relevant parameters missing in the bibliography is considered.•Financial framework of building holder has a strong impact on thermal comfort costs.•Control by PMV setpoints leads to better thermal comfort quality with lower costs.•The escalation of energy tariffs has a huge influence on thermal comfort cost.
Among the aspects with major impacts on the energy and environmental performance of a building, the thermal insulation of the opaque elements of its envelope stands out. This work assesses the ...influence of the application of thermal insulation to the opaque elements of the building’s envelope on the thermal comfort conditions indoors; moreover, the influence of the thermal insulation on the energy, environmental, and economic costs over the building’s complete life cycle is evaluated. For this purpose, the three most commonly used thermal insulating materials (expanded polystyrene—EPS, extruded polystyrene—XPS, and mineral wool—MW), thicknesses between 0 (without insulation) and 40 cm, five climates (hot, warm, moderate, cold, and very cold), and six types of use (apartment, housing, clinic, school, bank branch, and supermarket) were considered. EPS reveals itself to be the most promising thermal insulation material, both in economic and environmental terms, so it was selected for this study. The EPS’ optimal thickness depends on the building’s type of use, the climate, and the perspective from which the assessment is carried out (energy, environmental, or economic). The results show that the economically optimal thicknesses of thermal insulation are significantly lower than the corresponding ones in environmental terms. Furthermore, the application of thermal insulation to the opaque building’s envelope is more beneficial in energy and environmental terms than from an economic perspective.
Heat stress in many industrial workplaces imposes significant risk of injury to individuals. As a means of quantifying these risks, a comparison of four rationally developed thermoregulatory models ...was conducted. The health-risk prediction (HRP) model, the human thermal regulation model (HuTheReg), the SCENARIO model, and the six-cylinder thermoregulatory model (SCTM) each used the same inputs for an individual, clothing, activity rates, and environment based on previously observed conditions within the Portuguese glass industry. An analysis of model correlations was conducted for predicted temperatures (°C) of brain (TBrain), skin (TSkin), core body (TCore), as well as sweat evaporation rate (ER; Watts). Close agreement was observed between each model (0.81–0.98). Predicted mean ± SD of active phases of exposure for both moderate (TBrain 37.8 ± 0.25, TSkin 36.7 ± 0.49, TCore 37.8 ± 0.45 °C, and ER 207.7 ± 60.4 W) and extreme heat (TBrain 39.1 ± 0.58, TSkin, 38.6 ± 0.71, TCore 38.7 ± 0.65 °C, and ER 468.2 ± 80.2 W) were assessed. This analysis quantifies these heat-risk conditions and provides a platform for comparison of methods to more fully predict heat stress during exposures to hot environments.
The main objective of this work is the establishment of useful guide lines for secure fighting of high intensity fires, namely the determination of the influence of the personal protective clothing ...properties on safety during wildland firefighting operations. The physiological reaction of men exposed to these extreme conditions is obtained by numerical simulation of the heat and the mass transfer from an individual in the proximity of a fire line, as representative of a typical situation of a firefighter suppressing a high intensity fire. It is obvious that the impinging flux density depends on flame's dimensions and its properties as well as on the distance between the flame and those involved in fire suppression activities. The results obtained were calculated using a computer program based on a modified version of the Stolwijk thermoregulation model. Taking into account the time evolutions of skin, rectal and hypothalamus temperatures, a parametric study is presented about the importance of clothing properties, activity level and other external parameters in order to avoid the risk of significant undesired thermophysiological reactions within the firefighters. The results clearly show that, besides the improvement of personal protective clothing properties, the safety of firefighters is essentially related to good control of the exposure times to these high intensity radiation fluxes.
The objective of the present contribution is to assess the exposure to hot thermal environments in the Portuguese glass industry. For this purpose a field survey was carried out and the measurements ...took place in industrial units - five industries and nineteen workplaces were considered–so all the results are based on real working conditions. In order to assess the level of heat exposure the Wet Bulb Globe Temperature (WBGT) index and the Predicted Heat Strain (PHS) model, defined in ISO Standards 7243 (1989) and 7933 (2004), respectively, were used. According to the WBGT index, the results show that almost 80% of the workplaces under analysis are prone to heat stress conditions. If the PHS model is considered, the results highlight that the predicted and the maximum sweat rates present equal values in about 40% of the workplaces. In addition, in almost 25% of the workplaces the estimated rectal temperature was higher than 38°C, just for an exposure period of one hour. Thus, the present study brings to light the characteristics of the glass industry in terms of the occupational exposure to hot environments and places this activity sector as one of the most difficult to deal with.
This study addresses the measurement of the globe temperature. For this purpose, two globe thermometers with different diameters (50 and 150 mm) and a variety of thermal environmental conditions were ...considered. The assessments of the response times and of the influences of the globe diameter and the air velocity on the measured globe temperatures are discussed. The results of the response times clearly put in evidence that the values usually stated in the literature can be questioned and that longer measurement periods must be considered. In fact, response times >30 min were obtained in 68% of the tests performed. Moreover, differences >20ºC were obtained between the 150 and 50 mm sensors, highlighting the influence of the globe diameter. The analysis of the effect of the air velocity on the globe temperature shows mean relative differences >30% between tests in still air and with the higher air velocity considered (1.81 m s-1). On the basis of measurements carried out with the 50 mm globe, correction equations to the standard globe temperature for both natural and forced convection are proposed.
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