Cool roof for improving building energy efficiency in moderate climates

2020 ◽  
pp. 80-87
Author(s):  
Salem Algarni

At present, maintaining the thermal comfort in buildings is a significant challenge faced by majority of the developing countries. In this study, the impact of the cool roof on cooling and heating loads of buildings located in moderate climates is studied. The study presents a detailed simulation of a test room to estimate the impact of the cool roof on building performance in Abha, Saudi Arabia. Input parameters, such as building thermal properties, operation schedule, orientation, and climatic conditions were implemented. Furthermore, the experimental study of the test room was conducted at the main campus of King Khalid University, Abha. The results showed that the use of the cool roof reduced the energy consumption required for building cooling by approximately 52.5 kWh/m2/year; whereas the maximum increase in energy consumption owing to the winter heating is about 3.1 kWh/m2/year. The indoor thermal comfort was improved because the maximum indoor temperature decreased by 2.7 °C. The study concludes that the cool roof is an effective method to improve the indoor thermal comfort and reduce building energy consumption in Abha, Saudi Arabia and places with similar climatic conditions.

Author(s):  
Hamid Eskandari ◽  
Mehdi Saedvandi ◽  
Mohammadjavad Mahdavinejad

In this paper, the effect of an exterior shading element (Iwan) on energy consumption in four different climatic regions, and for different geographical directions, has been investigated numerically and experimentally. By applying different materials and techniques and creating various elements and spaces, architects make hard climatic conditions more tolerable for residents. Iwan is one of the cooling elements which is used in different forms and dimensions in the Islamic architecture. In the present research, Iwan has been introduced as a climatic element in traditional and contemporary architectures and its role in reducing the energy consumption in buildings has been studied. In this respect, first, the thermal loads of a building without Iwan are computed by means of EnergyPlus software. Then, four different forms of Iwan are added to the above-mentioned structure along the four principal geographical directions, and the effect of Iwan on the reduction of thermal loads is analyzed for four different climates. Finally, the design parameters of Iwan, in terms of depth and form, that can help reduce the thermal loads in different climatic conditions are presented. The results show that the best position for using an Iwan is the south direction and the use of Iwan in temperate & humid, hot & humid, cold & mountainous and hot & dry climates could reduce the energy consumption in buildings by 32%, 26%, 14%, and 29%, respectively.


2019 ◽  
Vol 11 (1) ◽  
pp. 266 ◽  
Author(s):  
Yupeng Wang ◽  
Hiroatsu Fukuda

The properties of building envelopes significantly affect indoor building energy consumption, indoor thermal comfort, and building durability. In the current standards for Japanese residential energy efficiency, insulation placement is not well regulated. Meanwhile, it is common in Japan to use air-conditioning intermittently, rather than having the units operate continuously. Therefore, considering specific Japanese lifestyles, we investigated insulation performance. In this research, we: (1) developed the interior insulation to include insulation on walls, ceilings and floors of building units (all of the interior surfaces) to achieve building energy savings by avoiding heat loss through thermal bridges; (2) discussed and demonstrated the effects of high heat capacitance for each of the building components and the thermal bridge by conducting building environmental simulations; (3) conducted simulations in seven cities in Japan and discussed the applicability of these different weather conditions; and (4) compared temperature distributions to investigate differences in indoor comfort with partial heating on winter nights. We demonstrated the energy saving and thermal comfort advantages of interior insulation. This research provides an innovative insulation style based on Japanese lifestyles that contributes to new energy-saving standards and formulations.


2011 ◽  
Vol 71-78 ◽  
pp. 3516-3519 ◽  
Author(s):  
Xue Bin Yang ◽  
De Fa Sun ◽  
Xiang Jiang Zhou ◽  
Ling Ling Cai ◽  
Ying Ji

The indoor thermal comfort and its effect on building energy consumption have been conducted by literature reviewing in the study. The linear relationship and the related formulations of various thermal comfort indictors are summarized to evaluate the human comfort. These parameters include predicted mean vote, thermal sensation vote, adaptive predicted mean vote, thermal comfort vote, and thermal acceptability. Under different climatic or regional conditions, both relationships between thermal comfort parameters and indoor or outdoor air temperature, and between comfort vote and another comfort parameter, are summarized for their definition and formulation. The comfort parameters such as local air speed, neutral temperature, PMV set point and others will directly impact the building energy usage. It is of significance to seek an optimal alternative for energy savings.


2018 ◽  
Vol 30 (2) ◽  
pp. 235-253 ◽  
Author(s):  
Salem Algarni

To raise awareness of the potential of passive technologies, this paper addresses the major problem of maintaining the comfort of the built environment in the harsh climate of Saudi Arabia by estimating the potential reduction in residential building energy consumption resulting from the use of highly reflective “cool roof” details. To conduct this estimate, the impacts of cool roof installation on the cooling and heating loads of residential buildings in 13 major selected sites in Saudi Arabia are estimated. It is found that the use of a cool roof reduces the annual energy consumption required for building cooling by between 110.3 and 181.9 kWh/m2, while the maximum increase in annual energy consumption due to winter heating of cool roof equipped buildings in hot-dry climates is only 4.4 kWh/m2. The results show that installing a cool roof in place of a typical or dirty roof yields a reduction in peak roof conduction. This investigation concludes that the use of the passive cool roof technology is an effective method for improving the thermal performance of a roof and thus reducing building energy consumption in the harsh climate of Saudi Arabia and similar extreme climates.


2018 ◽  
Vol 10 (10) ◽  
pp. 3609 ◽  
Author(s):  
Aiman Albatayneh ◽  
Dariusz Alterman ◽  
Adrian Page ◽  
Behdad Moghtaderi

Building energy assessment software/programs use various assumptions and types of thermal comfort models to forecast energy consumption. This paper compares the results of using two major thermal comfort models (adaptive thermal comfort and the predicted mean vote (PMV) adjusted by the expectancy factor) to examine their influence on the prediction of the energy consumption for several full-scale housing experimental modules constructed on the campus of the University of Newcastle, Australia. Four test modules integrating a variety of walling types (insulated cavity brick (InsCB), cavity brick (CB), insulated reverse brick veneer (InsRBV), and insulated brick veneer (InsBV)) were used for comparing the time necessary for cooling and heating to maintain internal thermal comfort for both models. This research paper exhibits the benefits of adopting the adaptive thermal model for building structures. It shows the effectiveness of this model in helping to reduce energy consumption, increasing the thermal comfort level for the buildings, and therefore reducing greenhouse emissions.


2019 ◽  
pp. 53-65
Author(s):  
Renata Domingos ◽  
Emeli Guarda ◽  
Elaise Gabriel ◽  
João Sanches

In the last decades, many studies have shown ample evidence that the existence of trees and vegetation around buildings can contribute to reduce the demand for energy by cooling and heating. The use of green areas in the urban environment as an effective strategy in reducing the cooling load of buildings has attracted much attention, though there is a lack of quantitative actions to apply the general idea to a specific building or location. Due to the large-scale construction of high buildings, large amounts of solar radiation are reflected and stored in the canyons of the streets. This causes higher air temperature and surface temperature in city areas compared to the rural environment and, consequently, deteriorates the urban heat island effect. The constant high temperatures lead to more air conditioning demand time, which results in a significant increase in building energy consumption. In general, the shade of the trees reduces the building energy demand for air conditioning, reducing solar radiation on the walls and roofs. The increase of urban green spaces has been extensively accepted as effective in mitigating the effects of heat island and reducing energy use in buildings. However, by influencing temperatures, especially extreme, it is likely that trees also affect human health, an important economic variable of interest. Since human behavior has a major influence on maintaining environmental quality, today's urban problems such as air and water pollution, floods, excessive noise, cause serious damage to the physical and mental health of the population. By minimizing these problems, vegetation (especially trees) is generally known to provide a range of ecosystem services such as rainwater reduction, air pollution mitigation, noise reduction, etc. This study focuses on the functions of temperature regulation, improvement of external thermal comfort and cooling energy reduction, so it aims to evaluate the influence of trees on the energy consumption of a house in the mid-western Brazil, located at latitude 15 ° S, in the center of South America. The methodology adopted was computer simulation, analyzing two scenarios that deal with issues such as the influence of vegetation and tree shade on the energy consumption of a building. In this way, the methodological procedures were divided into three stages: climatic contextualization of the study region; definition of a basic dwelling, of the thermophysical properties; computational simulation for quantification of energy consumption for the four facade orientations. The results show that the façades orientated to north, east and south, without the insertion of arboreal shading, obtained higher values of annual energy consumption. With the adoption of shading, the facades obtained a consumption reduction of around 7,4%. It is concluded that shading vegetation can bring significant climatic contribution to the interior of built environments and, consequently, reduction in energy consumption, promoting improvements in the thermal comfort conditions of users.


2020 ◽  
pp. 50-64
Author(s):  
Kuladeep Kumar Sadevi ◽  
Avlokita Agrawal

With the rise in awareness of energy efficient buildings and adoption of mandatory energy conservation codes across the globe, significant change is being observed in the way the buildings are designed. With the launch of Energy Conservation Building Code (ECBC) in India, climate responsive designs and passive cooling techniques are being explored increasingly in building designs. Of all the building envelope components, roof surface has been identified as the most significant with respect to the heat gain due to the incident solar radiation on buildings, especially in tropical climatic conditions. Since ECBC specifies stringent U-Values for roof assembly, use of insulating materials is becoming popular. Along with insulation, the shading of the roof is also observed to be an important strategy for improving thermal performance of the building, especially in Warm and humid climatic conditions. This study intends to assess the impact of roof shading on building’s energy performance in comparison to that of exposed roof with insulation. A typical office building with specific geometry and schedules has been identified as base case model for this study. This building is simulated using energy modelling software ‘Design Builder’ with base case parameters as prescribed in ECBC. Further, the same building has been simulated parametrically adjusting the amount of roof insulation and roof shading simultaneously. The overall energy consumption and the envelope performance of the top floor are extracted for analysis. The results indicate that the roof shading is an effective passive cooling strategy for both naturally ventilated and air conditioned buildings in Warm and humid climates of India. It is also observed that a fully shaded roof outperforms the insulated roof as per ECBC prescription. Provision of shading over roof reduces the annual energy consumption of building in case of both insulated and uninsulated roofs. However, the impact is higher for uninsulated roofs (U-Value of 3.933 W/m2K), being 4.18% as compared to 0.59% for insulated roofs (U-Value of 0.33 W/m2K).While the general assumption is that roof insulation helps in reducing the energy consumption in tropical buildings, it is observed to be the other way when insulation is provided with roof shading. It is due to restricted heat loss during night.


2017 ◽  
Vol 8 (5) ◽  
pp. 221
Author(s):  
Sugiono Sugiono ◽  
Suluh E. Swara ◽  
Wisnu Wijanarko ◽  
Dwi H. Sulistyarini

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