Effect Of Thermal Mass Research Articles

Effect of Thermal Mass on Fuel Consumption of Solid Biomass Cooking Stoves

The use of rudimentary cooking stoves has harmful consequences not only for the health of users but also for the environment. Faced with these problems, studies are being carried out to develop more efficient stoves. The materials used for the construction and/or design of cooker range from heavy materials to light materials. However, cookers built from heavy materials accumulate a portion of the heat produced in their walls. The objective of this study is to demonstrate the influence of thermal mass on the fuel consumption of cookers. The study concerns not only a set of stoves taken from the literature but also a set of stoves that we tested. The two sets of stoves differ in terms of their characteristics: Single-pot wood stove without chimney or skirt, Single-pot wood stove without chimney with skirt, Multi-pot wood stove with chimney, Single-pot charcoal stove without chimney or skirt, etc. The adapted approach consists of classifying all stoves by category. Then, for each category, the mass of the cookers as well as the quantity of fuel necessary for the same cooking task will be compared. It appears that for all the stoves taken from the literature and all the stoves submitted to the test, in each of the categories, the higher the mass of the stove, the more fuel it consumes for the same cooking task.

Diminishing benefits of thermal mass in Iranian climate: Present and future scenarios

Thermal mass, a pivotal element in a building's performance, functions as an indoor thermal buffer. While literature underscores its advantages, the enduring impact of thermal mass amid climate change remains uncertain. This study methodically assesses thermal mass effects in 21 Iranian cities across contemporary and future climates, juxtaposing heavyweight and lightweight constructions. The EPSAP algorithm, a generative building design method, created a dataset of two-story single-family houses. Cooling and heating demands were evaluated in EnergyPlus, accounting for current and future system design efficiencies. Future climates were simulated using EC-Earth3 model estimations for the SSP5-8.5 scenario in 2050 and 2080 timeframes. The findings reveal that the energy efficiency advantage of heavyweight over lightweight buildings will diminish by up to 0.60 kW·h·m−2 in 2050 (40 % less than the present-day climate difference between constructions) and 0.93 kW·h·m−2 in 2080 (63 %) for cities in central and southern regions. The performance differences between constructions will sometimes be null, making thermal mass negligible. Conversely, only three cities in Northern Iran exhibit an opposing trend for mid to very-high thermal transmittances. Regarding building geometry, heavyweight construction correlates strongly with indexes related to building compactness, while lightweight construction aligns more with glazing-related indexes. However, as climates warm or we move towards warmer regions, discernible differences between lightweight and heavyweight constructions vanish for both shape- and glazing-related indexes. In conclusion, although the use of thermal mass will be less effective, building design professionals will have greater latitude for innovative construction and design solutions.

Exploring building component thermal storage performance for optimizing indoor thermal environment – A case study in Beijing

Optimizing the thermal storage of building components is crucial for improving indoor thermal conditions and reducing heating energy consumption. However, existing studies often overlook the effect of the substantial thermal mass in common building components, each storing different levels of heat. This study finds that considering this thermal mass and its energy during the building design phase can significantly save insulation material costs and heating energy consumption.Our work is built upon the analysis of the thermal behaviors of real buildings. We collected data from 43 representative rooms in cold regions and utilized Multiple Linear Regression models to examine how solar radiation and outdoor temperatures affect thermal mass in external walls, internal walls, and floors. We also used Probabilistic Density Distribution models to study heat transfer within these components. Subsequently, we applied Conduction Transfer Functions with just a 2.08% error rate to derive an optimal passive design strategy for year-round use of building thermal mass.Experimental results show that our strategy saves more energy by 0.78 kWh/m2 without increasing the insulation material cost, exceeding current standards. In cold regions, our study suggests focusing on mitigating the negative effects of building thermal mass, which offers greater energy savings than exploiting its positive aspects. Moreover, our findings can be easily integrated into the optimization of physical properties like thermal capacity and insulation for either improving stock buildings or designing new buildings, further enhancing their energy and material efficiency.

Effect of Latent Heat by Phase Transformation on the Thermal Behavior of Steel Billet during Heating.

The effect of latent heat via phase transformation on the thermal behavior of a billet was investigated during the heating process. The latent heat of the billet strongly affected the temperature distribution of the billet during heating, although the heating rate of the billet was not high during the process. The temperature profile of the center region of the steel billet with latent heat had a strong flat shape compared with the other regions, as the heat supply to the center region was limited during the heating process owing to the finite thermal conductivity and mass effect of the billet. The latent heat by phase transformation typically occurred in the middle stage of heating, and the latent heat increased the temperature deviation of the billet during heating owing to the delay in the temperature rise at the center region of the billet. During the phase transformation of carbon steels during heating, the gas temperature needs to be low to reduce the temperature deviation or thermal stress of the billet. Industrial hot rolling mills are required to consider the latent heat by phase transformation of the billet to properly design the heating pattern for the billet. The heating pattern in the reheating furnace should be varied with the materials to obtain a high heating quality for the billet.

Hydrate Formation from Joule Thomson Expansion Using a Single Pass Flowloop

Hydrate risk management is critically important for an energy industry that continues to see increasing demand. Hydrate formation in production lines is a potential threat under low temperature and high-pressure conditions where water and light gas molecules are present. Here, we introduce a 1-inch OD single-pass flow loop and demonstrate the Joule-Thomson (JT) expansion of a methane-ethane mixture. Initially, dry gas flowed through the apparatus at a variable pressure-differential. Larger pressure differentials resulted in more cooling, as predicted by standard thermodynamic models. A systematic deviation noted at higher pressure differentials was partially rectified through corrections incorporating heat transfer, thermal mass and kinetic energy effects. A wet gas system was then investigated with varying degrees of water injection. At the lowest rate, hydrate plugging occurred close to the expansion point and faster than for higher injection rates. This immediate and severe hydrate plugging has important implications for the design of safety relief systems in particular. Furthermore, this rate of plugging could not be predicted by existing software tools, suggesting that the atomization of liquids over an expansion valve is a critical missing component that must be incorporated for accurate predictions of hydrate plug formation severity.

Effects of thermal mass on transient thermal performance of concrete-based walls and energy consumption of an office building

Reducing energy consumption and Greenhouse Gas (GHG) emissions is an essential part of the clean growth and climate change framework recently developed by the Canadian government, which emphasizes the importance of energy-efficient building constructions. In this paper, the effects of thermal mass and placement of the thermally massive layer within wall assemblies on the transient thermal performance of walls and energy performance of a case study office building were studied. Three climate conditions representative of the heating-dominated, temperate, and cooling-dominated climates were considered. As for the assessment of energy demands, two cases for the indoor air temperature were taken into account: (i) indoor temperature was maintained at 20°C throughout the year, and (ii) during summertime, there was a set-point of 24°C and a setback of 35°C during the rest of the day while during wintertime, the set-point and setback values were 22°C and 18°C, respectively. The cases were compared according to the resulting decrement factor, the time required to reach quasi-steady state conditions, amplitudes of changes of heat fluxes and indoor surface temperatures, and the energy demands. The results showed that, for the cases studied, the wall, for which the thermally massive layer is not directly exposed to the indoor and outdoor climate conditions, resulted in the lowest decrement factor, the minimum amplitude of changes of heat fluxes and indoor surface temperatures, and maximum time required to reach quasi steady-state conditions. As for the energy performance, on the other hand, the wall, for which the thermally massive layer is exposed to the interior and exterior climate conditions, performed best amongst the cases investigated.

Chemical reaction, Dufour and Soret effects on the stability of magnetohydrodynamic blood flow conveying magnetic nanoparticle in presence of thermal radiation: A biomedical application

Nowadays ferrofluids (magnetic nanofluids) are at the center of many researches because of their major biomedical applications such as drug delivery and cancer treatment. The effects of chemical reaction, temperature gradient induced mass transfer and concentration gradient induced heat transfer on the stability of ferrofluid flow are of great importance. This paper deals with a stability analysis of a ferrofluid composed of blood as base fluid and magnetic nanoparticles. The study integrates the effects of chemical reactions, the effects of mass transfer (Soret effect), the effects of heat transfer (Dufour effect) and the effects of the Buoyancy force. The flow is exposed to a magnetic field and thermal radiation. A system of eigenvalue equations governing the evolution of disturbances is derived by assuming a normal mode analysis. This system of equations is then solved numerically by the method of collocation. It appears from this study that the addition of nanoparticles to the blood increases its inertia, which dampens the amplitude of the disturbances and stabilizes the flow. The Casson parameter affects the stability of the flow by increasing the amplitude of the disturbances, which reflects its destabilizing effect. It appears from this study that taking into account the non-Newtonian nature of blood is very important when modeling the dynamics of the system because it shows more important and very different results than when blood is treated as a Newtonian fluid. The chemical reaction between the fluid and the nanoparticles leads to the redistribution of disturbances within the flow, which amplifies the instabilities and reflects the destabilizing character of the chemical reaction. On the other hand, temperature gradient induced mass transfer effects and concentration gradient induced heat transfer effects play an essential role on the stability of the flow because they attenuate the amplitude of the disturbances in the flow. The Darcy number exhibits a stabilizing effect on the flow. It appears from this analysis that the porosity of the medium increases the contact surface between the fluid and the nanoparticles. Buoyancy forces, thermal radiation parameter and wave number contribute to the stability of the flow. The magnetic field through the Lorentz force decreases the kinetic energy of the flow, which dissipates the disturbances and thus reflects the stabilizing character of the magnetic field. It should be noted that heat and mass transfer on magnetohydrodynamic flows through porous media taking into consideration the effect of chemical reaction appears in many natural and artificial transport processes in several branches of science and engineering applications. This phenomenon plays an important role in the chemical industry, power and cooling industry for drying, chemical vapor deposition on surfaces, cooling of nuclear reactors and petroleum industry. The effects of thermal radiation, mass and heat transfer are used in many situations in biomedical engineering and aerospace engineering.

Developing Green–Building Design Strategies in the Yangtze River Delta, China through a Coupling Relationship between Geomorphology and Climate

Many studies have developed green strategies and technologies for urban construction, but they sometimes ignored the intensive and dynamic relationships between people, buildings and the natural environment. This study focused on how to generate green building design strategies dealing with a coupling relationship between geomorphology and climate, which took an insight into the built environment in a particular locality of the Yangtze River Delta region in China. First, we imported climatic data from six cities into a bioclimatic evaluation tool, named ‘Weather Tool’, to assess the effectiveness of the existing passive design strategies (passive solar heating, thermal mass effects, exposed mass and night purge ventilation, natural ventilation, direct evaporative cooling and indirect evaporative cooling). Second, we employed the topological method to identify the characters of the vernacular dwellings by interpreting their adaptations to the local topographical and climatic conditions. Consequently, the green building design strategies in the Yangtze River Delta region were developed through the macro, middle and micro levels to examine group patterns, single-building forms and building components in a particular locality. The main findings were shown as follows: (1) the common passive strategies played a role with different effects in the Yangtze River Delta region, which acted as a basis for choosing the most effective strategies; (2) the local dwellings presented a comprehensively sustainable paradigm with architectural prototypes that could be selectively inherited and applied in contemporary design. (3) Those particular strategies, which were evaluated through bioclimatic tools and developed from the vernacular dwellings, gave specific suggestions on green building design in the Yangtze River Delta region, providing approaches for architects and developers to promote more environmentally responsive sustainable development.

Developing analytical model for nighttime cooling of internal thermal mass

Nighttime mechanical ventilation of internal building thermal mass has the potential to create energy flexibility by shifting peak cooling demand. The research on nighttime cooling of internal thermal mass is limited due to lacking simplified models by considering mass dimension and real-world discrete climate data like hourly outdoor air temperatures. This study develops an analytical model for nighttime cooling of internal thermal mass with a constant air change rate and hourly varied air temperatures. The analytical model is verified by both numerical, conduction transfer function methods, and ANSI/ASHRAE Standard 140-Case 600. The analytical model is applied to quantify the free cooling energy storage in 48 selected U.S. cities in different climate zones and in the 16 climate zones of California. Among the 48 cities, the maximum free cooling energy storage is reported in Santa Fe, NM with a total free cooling energy storage of 19.1 kWh m-2 a-1 and a net free cooling energy storage of 3.88 kWh m-2 a-1. Coastal regions in California are not suitable for nighttime ventilation of internal thermal mass. The maximum total free cooling energy storage in California achieves 27.5 kWh m-2 a-1, while the maximum net free cooling energy storage is 6.11 kWh m-2 a-1. The analytical model has a potential to be integrated into whole building energy simulation software to improve the calculation of the effect of internal thermal mass.

Comparative life cycle assessment of a reinforced concrete residential building with equivalent cross laminated timber alternatives in China

With the development of mass timber, cross laminated timber (CLT) has gradually become a sustainable alternative to conventional building materials to alleviate the increasing energy consumption and carbon emissions by the building sector. This study aims to explore the life cycle greenhouse gas emissions (LCGHGE) and life cycle primary energy (LCPE) of three high-rise residential buildings in the cold region of China through a life cycle assessment approach. The three buildings are conventional reinforced concrete (RC), CLT and hybrid CLT buildings. The results show that CLT and hybrid CLT buildings produce 15.00% and 10.77% lower LCGHGE, respectively, compared to the RC building within a 50-year service life. A clear difference in greenhouse gas (GHG) emissions and primary energy (PE) in the product and construction stages is visible, with 46.52% and 37.24% of embodied GHG emissions reduced in CLT and hybrid CLT buildings, respectively, compared to the RC building. In the operational stage, RC building has lower PE and GHG emissions to CLT alternatives. The thermal mass effect has led to a 2.25% and 2.12% PE increase for space heating and cooling in CLT and hybrid CLT buildings, respectively, compared to the RC building. For the End-of-Life (EoL) stage, CLT demonstrates great recycling potential and biomass residues. The sensitivity analysis shows that the design of the low U-value of the building envelope and high-efficiency energy systems has a significant relationship with energy reduction during the operational phase of the three buildings, magnifying the impacts of the initial and EoL stages. • CLT and hybrid CLT buildings produce 15.00% and 10.77% less LCGHGE than RC buildings in Tianjin, China, respectively. • Mass timber construction shows great advantages over RC buildings in the P&C/EoL stage. • The operational GHG emissions and PE of CLT and hybrid CLT buildings were 12–13% higher than those of the RC building. • Energy-efficient methods can enhance the LCA performance of hybrid CLT building.

Investigation on the cooling performance of a buoyancy driven earth-air heat exchanger system and the impact on indoor thermal environment

The feasibility and cooling performance of a pure buoyancy-driven earth-air heat exchanger system (B-EAHE) with the assistance of combined effect of solar chimney and thermal mass were verified and revealed by a full-scale experimental study. The experimental results showed that the EAHE pipe diameter plays an important role in the system performance, and the airflow rates reach peak values of approximately 252 m3/h and 166 m3/h for the EAHE pipes with diameters of 0.3 m and 0.2 m, respectively. The air temperature differences between the inlet and outlet of the EAHE were approximately 12.5 °C and 13.0 °C in maximum, and 4.8 °C and 4.78 °C in average for the EAHE pipes with diameters of 0.2 and 0.3 m. In addition, the amplitude of indoor air temperature was further attenuated under the regulation of the B-EAHE system. The air temperature inside reference chamber varies from 28.3 to 35.1 °C, while the air temperature inside test chamber with 0.3 m diameter pipe ranges from 28.5 to 30 °C, which is approximately 2 °C lower than that for test chamber with 0.2 m diameter pipe. Moreover, higher energy saving potential is justified by the 0.3 m diameter pipe with peak cooling capacity of 1179 W compared with the 0.2 m diameter pipe with peak cooling capacity of 629 W. It is concluded that the B-EAHE system is able to achieve 24 h periodically fluctuating natural ventilation and passive cooling, and to improve the indoor thermal environment greatly in hot summer conditions.

Challenges and Capabilities in Estimating Snow Mass Intercepted in Conifer Canopies With Tree Sway Monitoring

AbstractSnowpack accumulation in forested watersheds depends on the amount of snow intercepted in the canopy and its partitioning into sublimation, unloading, and melt. A lack of canopy snow measurements limits our ability to evaluate models that simulate canopy processes and predict snowpack. We tested whether monitoring changes in wind‐induced tree sway is a viable technique for detecting snow interception and quantifying canopy snow water equivalent (SWE). Over a 6 year period in Colorado, we monitored hourly sway of two conifers, each instrumented with an accelerometer sampling at 12 Hz. We developed an approach to distinguish changes in sway frequency due to thermal effects on tree rigidity versus intercepted snow mass. Over 60% of days with canopy snow had a sway signal that could not be distinguished from thermal effects. However, larger changes in tree sway could not generally be attributed to thermal effects, and canopy snow was present 93%–95% of the time, as confirmed with classified PhenoCam imagery. Using sway tests, we converted changes in sway to canopy SWE, which were correlated with total snowstorm amounts from a nearby SNOTEL site (Spearman r = 0.72 to 0.80, p < 0.001). Greater canopy SWE was associated with storm temperatures between −7°C and 0°C and wind speeds less than 4 m s−1. Lower canopy SWE prevailed in storms with lower temperatures and higher wind speeds. Monitoring tree sway is a viable approach for quantifying canopy SWE, but challenges remain in converting changes in sway to mass and distinguishing thermal and snow mass effects on tree sway.

Mass-derivative relations for leptogenesis

In this work, a diagrammatic representation of thermal mass effects is derived from the S-matrix unitarity both in the classical and quantum Boltzmann equations. Within the example of the seesaw type-I leptogenesis, we discuss the connection of the Higgs thermal mass and the cancelations of infrared divergences in zero- and finite-temperature calculations of the right-handed neutrino decay and scattering processes.

Thermal Mass Effect on the Solution Cooling Rate and on HIPped Astroloy Component Properties.

Astroloy is a Ni-based superalloy with high-volume fraction of γ′, which gives high temperature properties but reduces its forgeability. Therefore, powder metallurgy manufacturing processes such as Near Net Shape HIPping are the most suitable manufacturing technology for Astroloy. However, NNSHIP has its own drawbacks, such as the formation of prior particle boundaries (PPBs), which usually tend to decrease material mechanical properties. The detrimental effect of PPBs can be reduced by optimizing the entire HIP processing route. Conventional HIP cycles have very low cooling rates, especially in big components from industry, and thus a series of post-heat treatments must be applied in order to achieve desirable microstructures and improve the mechanical properties. Standard heat treatments for Astroloy are long and tedious with several steps of solutioning, stabilization and precipitation. In this work, two main studies have been performed. First, the effect of the cooling rate after the solutioning treatment, which is driven by the materials’ thermal mass, on the Astroloy microstructure and mechanical properties was studied. Experimental analyses and simulation techniques have been used in the present work and it has been found that higher cooling rates after solutioning increase the density of tertiary γ′ precipitates by 85%, and their size decreases by 22%, which leads to an increase in hardness from 356 to 372 HB30. This hardness difference tends to reduce after subsequent standard heat treatment (HT) that homogenizes the microstructure. The second study shows the effect of different heat treatments on the microstructure and hardness of samples with two different thermal masses (can and cube). More than double the density of γ′ precipitates was found in small cubes in comparison with cans with a higher thermal mass. Therefore, the hardness in cubes is between 4 and 20 HB 30 higher than in large cans, depending on the applied HT.

CFD study of supercritical flow stability in two heated parallel channels with wall thermal mass effects

Three-dimensional (3D) numerical simulations were carried out of two vertical heated parallel channel experiments using ANSYS CFX to investigate the effects of wall energy storage on the system's stability boundary of a supercritical water up-flow system. Oscillatory instability boundaries of six experimental cases with two different wall thicknesses and uniform power distribution were produced, assessed and discussed. The 3D numerical solutions of the instability boundary with wall energy storage are in very good agreement with the experiments, which is believed to be a significant advance on previous work in this area. Results from a 1D linear code with wall thermal energy storage are also included for reference. The commonly used modelling assumption of circumferentially symmetric flow was found to be inadequate when modelling the wall heat storage. Temporal and spatial independence were ensured for the reported cases. The prediction of the oscillation periods obtained with CFX are also discussed.

Effect of thermal mass of insulated and non-insulated walls on building thermal performance and potential energy saving

The presented study aims to evaluate the effect of thermal mass in heavyweight construction in residential buildings in Palestine on indoor thermal environment using a building performance simulation tool. The most used residential building types, shapes and sizes were used as typical models for indoor environment performance simulation. The paper used a sensitivity analysis for four different scenarios according to the location of thermal insulation in the wall for two climatic zones, when no heating and cooling was used. The building material’s thermal properties, infiltration, activities, time schedule, electric lighting and glazing selection were based on onsite studies. The results show that the internal thermal mass of the studied buildings influences their thermal performance and future potential energy demand for heating and cooling. Buildings with insulation positioned on the outside, with high thermal mass and high thermal time constant showed the best thermal performance for different climatic zones, whereas buildings without thermal insulation or with insulation from the inside showed the worst thermal performance. The position of thermal insulation will affect potential energy demand for heating and cooling in the residential buildings.

Component sequence and thermal mass effects on the transient thermal performance of concrete walls

The increased requirements of buildings to reduce energy use have highlighted the importance of accounting for all factors that influence energy use in buildings. One consideration that requires further study in the envelope design of concrete-based wall assemblies is the placement of the thermal mass layer. In this study, two thermally massive walls, Insulated Concrete Form (ICF) and tilt-up walls, with the same thermal resistance but different sequencing of layers are investigated. In addition, a wall made of a homogeneous insulation layer with an identical thermal resistance was considered to further investigate the thermal mass effect on the potential for energy savings. Results of the numerical simulations performed using COMSOL Multiphysics® software indicate that, for the transient scenarios investigated, thermal mass can contribute to shifting and dampening peak heating and cooling loads, as well as saving energy. Also, less intense fluctuations were observed in the heat fluxes when considering the ICF wall. Energy savings during the primary seasons (i.e. winters in Montreal and summers in Miami) are found to be marginal but the existence of a thermally massive layer considerably reduced the demands during secondary seasons i.e. summers in Montreal and winters in Miami.

Effect of geometry and thermal mass of Direct-Metal-Laser-Sintered aluminium Heat Exchangers filled with phase change materials on Lithium-Ion cells’ passive cooling

• Direct-Metal-Laser-Sintered (DMLS) aluminium Heat Exchangers (HEX) • DMLS HEX filled with Phase Change Materials (PCM) for Li-Ion cells isothermalisation. • Effect of PCM mass and HEX geometry on Li-Ion cells isothermalisation. • Single discharge and consecutive charge/discharge cycles tests conducted. This study investigates the effect of mass and geometry as design parameters of a Lithium-Ion (Li-Ion) cell Thermal Management System (TMS) based on a Direct-Metal-Laser-Sintered (DMLS) structure filled on Phase Change Material (PCM). As part of a TMS, complex heat exchanger geometries are produced using DMLS technique, filled with a PCM, and experimentally tested using an established methodology. The design parameters investigated are PCM mass and DMLS heat exchanger geometry to assess the effects of increased thermal energy storage capacity and enhanced equivalent thermal conductivity respectively on the overall performance of a Li-Ion pouch cell. Constant discharge rate tests and stress sequences are used to reproduce realistic Li-Ion cell operating conditions. It has been shown that all PCM TMS effectively improve the isothermalisation of the cell under a single discharge at rate 3C compared to natural convection and decreased the cell maximum temperature by at least 5 °C. The enhanced heat transfer performance of finned designs further improves the temperature uniformity and decreases the cell maximum temperature. When tested under stress sequences, the TMS characterised by a higher thermal mass maintained functional isothermalisation for 5 cycles; this is an increase of two cycles than for the TMS with a lower thermal mass. By using a Pareto front analysis based on thermal and geometrical variables, specific designs are indicated as the best combination of thermal performance and additional weight for single discharge tests (i.e., intermittent load) and stress sequences (i.e., constant load).

Effect of thermal mass, night ventilation and window shading on summer thermal comfort of buildings in a temperate climate

Night ventilation and external blinds are the most commonly used passive methods to protect buildings from overheating during high summer temperatures. Another recommended measure is high thermal inertia of buildings. The aim of the study was to compare the effectiveness of night ventilation, external blinds and thermal mass during a heat wave on the thermal performance of a building during a heat wave in a temperate climate. Increasing the thermal mass of the room from light to very heavy without night ventilation resulted in a reduction of the average peak temperature by 3.7 K in a day and 1.2 K by night. The activation of night ventilation in a light room resulted in a reduction of the average value of the peak temperature by 1.5 K during the day and 5.9 K at night. Increase of thermal mass from light to heavy and night ventilation from 0.6 to 10 ACH led to decrease of average peak temperature by 4.7 K in a day and 4.6 K by night. The simultaneous increase of thermal mass, activation of night ventilation and closing of external blinds resulted in lowering the average peak temperature by 7.4 K in a day and 6.3 K by night. The analysis of the test results indicates that the high thermal mass and the closing of the external blinds reduces the diurnal variations of the indoor temperature, while the activation of nighventilation increases it significantly, especially for lightweight construction.

The environmental response of office buildings from the Brazilian bioclimatic modernism in São Paulo: the case study of Complexo Conjunto Nacional – CCN (1962)

In commercial buildings from the Brazilian modernism (1930 -1964), narrow plans allowed for good daylight and natural ventilation. However, little is known about the environmental performance of those buildings. Economic pressures led to a proliferation of tall office buildings of larger floors and sealed facade, with major impacts on buildingś thermal behaviour. In this context, the objective of this technical study is to draw lessons from the performance of the iconic office building of Complexo Conjunto Nacional (1963), in São Paulo (24oS), with focus on its thermal response. Since the case-study building has no external shading, the counter effect of thermal mass from the concrete structure, coupled with the potential of natural ventilation, was examined by means of fieldwork and analytical studies. The relation between orientation, solar exposure and daylight was also addressed by measurements as well as the impact of operable windows in the internal acoustic environment. Thermodynamic simulations revealed that comfort can be achieved for more than 85% of occupied hours in the hottest month of the year, with passive means. Daylight measurements showed that illuminance levels remain within the visual comfort range, when direct solar radiation is not impinging on windows. Noise levels above the recommended by national standards were registered with windows opened and closed. Nevertheless, regardless the acoustic conditions, fieldwork confirmed that some occupants choose to open windows for natural ventilation at various heights in both buildingś orientations. The work presented here is part of the research project quoted in Gonçalves et al. (2018).