Effective R-value of enclosed reflective space for different building applications

2019 ◽  
Vol 43 (5) ◽  
pp. 398-427 ◽  
Author(s):  
Hamed H Saber ◽  
Wahid Maref ◽  
Ali E Hajiah
Keyword(s):  
Heat Flow ◽  
Thermal Performance ◽  
Accurate Determination ◽  
Energy Performance ◽  
Climatic Conditions ◽  
Operating Conditions ◽  
Building Envelopes ◽  
Inclination Angles ◽  
R Value ◽  
Enclosed Space

Many parts of the building envelopes contain enclosed airspaces. Also, the insulating glass units in fenestration systems, such as curtain walls, windows, and skylight devices, contain enclosed spaces that are normally filled with air or heavy gas such as argon, xenon, or krypton. The thermal resistance (R-value) of an enclosed space depends mainly on the type of the filling gas, emissivity of all surfaces that bound the space, the size and orientation of the space, the direction of heat flow through the space, and the respective temperatures of all surfaces that define the space. Assessing the energy performance of building envelopes and fenestration systems, subjected to different climatic conditions, requires accurate determination of the R-values of the enclosed spaces. In this study, a comprehensive review is conducted on the thermal performance of enclosed airspaces for different building applications. This review includes the computational and experimental methods for determining the effective R-value of enclosed reflective airspaces. Also, the different parameters that affect the thermal performance of enclosed airspaces are discussed. These parameters include the following: (a) dimensions, (b) inclination angles, (c) directions of heat flow, (d) emissivity of all surfaces that bound the space, and (e) operating conditions. Moreover, numerical simulations are conducted using a previously developed and validated model to investigate the effect of the inclination angle, direction of heat transfer, and the coating emissivity on the R-values of enclosed spaces when they are filled with different types of gases.

Practical correlation for thermal resistance of 45° sloped-enclosed airspaces with upward heat flow for building applications

2021 ◽  
pp. 174425912110099
Author(s):  
Hamed H Saber
Keyword(s):  
Heat Flow ◽  
Aspect Ratio ◽  
Thermal Resistance ◽  
Accurate Determination ◽  
Thin Sheet ◽  
Energy Performance ◽  
Operating Conditions ◽  
Building Components ◽  
R Value

Assessing the energy performance of building components with enclosed airspaces requires accurate determination of the thermal resistance ( R-value) of the airspaces. The R-value of enclosed airspace depends on its size and orientation, direction of heat transfer through the airspace, and temperatures and emissivities of all surfaces that define the airspace. In previous studies, practical correlations were developed to determine the R-values for vertical enclosed airspaces, horizontal enclosed airspaces with upward heat flow and downward heat flow, and 30° and 45° sloped-enclosed airspaces with downward heat flow. However, to the authors’ best knowledge, there is no such practical correlations available to determine the R-values for wide ranges of dimensions and operating conditions for 30° and 45° sloped-enclosed airspaces with upward heat flow. This paper focused on the thermal performance of 45° sloped-enclosed airspaces with upward heat flow, and the predicted R-values were compared with the R-values provided in ASHRAE Handbook of Fundamentals at different conditions. The dependence of the R-value on the aspect ratio of the enclosed airspaces was also investigated. As well, considerations were given to quantify the potential increase in the R-value of enclosed airspace when a thin sheet having different values of emissivity on both sides was placed in the middle of the airspace. The results showed that depending on the value of the effective emittance and the thickness of the airspace, the R-value could be tripled by incorporating thin a sheet in the middle of the enclosed airspace. Finally, practical correlation were developed to determine the effective R-values of 45° sloped-enclosed airspaces with upward heat flow for wide ranges of aspect ratio, temperature difference across the airspace, mean temperature, and effective emittance. The results showed that the calculated R-values using this correlation were in good agreement with the predicted R-values.

scholarly journals Solar Gain Influence on the Thermal and Energy Performance of Existing Mosque Buildings in the Hot-Arid Climate of Riyadh City

2021 ◽  
Vol 13 (6) ◽  
pp. 3332
Author(s):  
Ahmed Ali A. Shohan ◽  
Hanan Al-Khatri ◽  
Ahmed Ali Bindajam ◽  
Mohamed B. Gadi
Keyword(s):  
Thermal Performance ◽  
Thermal Conditions ◽  
Energy Performance ◽  
Climatic Conditions ◽  
Future Research ◽  
Analysis Software ◽  
Riyadh City ◽  
Hot Arid Climate ◽  
Reported Study ◽  
Proper Design

The required cooling energy in buildings exceeds 65% of the total energy consumed inside buildings under the extreme climatic conditions of Saudi Arabia. The proper design of buildings’ envelopes has a considerable potential in reducing such levels, especially in public buildings. The reported study evaluated the thermal performance of mosque buildings with focus on the solar gains through the envelope elements. Computer simulations were carried out using Thermal Analysis Software (TAS). In addition, the thermal and comfort votes of the worshippers in one mosque were collected. The findings revealed uncomfortable thermal conditions, especially during summer months. The required cooling energy ranged between 37% and 55% in the investigated mosques. Investigating the solar gains of the envelope elements of one mosque indicated that the roof is the largest contributor to solar gain, which highlights the potential for future research to explore new constructional alternatives with the aim of improving the roofs’ thermal performance.

scholarly journals Evaluation of School Building Energy Performance and Classroom Indoor Environment

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2489 ◽  
Author(s):  
Jitka Mohelníková ◽  
Miloslav Novotný ◽  
Pavla Mocová
Keyword(s):  
Energy Consumption ◽  
Energy Performance ◽  
Climatic Conditions ◽  
School Buildings ◽  
School Building ◽  
Indoor Climate ◽  
Building Stock ◽  
Building Envelopes ◽  
Existing Building ◽  
School Renovation

Existing building stock represents potential for energy saving renovations. Energy savings and indoor climate comfort are key demands for sustainable building refurbishment. Especially in schools, indoor comfort is an extremely important issue. A case study of energy consumption in selected school buildings in temperate climatic conditions of Central Europe region was performed. The studied buildings are representatives of various school premises constructed throughout the last century. The evaluation was based on data analysis of energy audits. The goal was aimed at assessment of the school building envelopes and their influence on energy consumption. One of the studied schools was selected for detailed evaluation. The school classroom was monitored for indoor thermal and visual environments. The monitoring was performed to compare the current state and renovation scenarios. Results of the evaluation show that the school buildings are highly inefficient even if renovated. Indoor climate in classrooms is largely influenced by windows. Solar gains affect interior thermal stability and daylighting. Thermal insulation quality of building envelopes and efficient solar shading systems appear to be fundamental tasks of school renovation strategies.

scholarly journals Investigating The Impact Of Thermal Mass Towards Energy Efficient Housing In Canada

2021 ◽  
Author(s):  
Tasnuva Ahmed
Keyword(s):  
Energy Consumption ◽  
Energy Efficient ◽  
Energy Performance ◽  
Climatic Conditions ◽  
Simulation Software ◽  
High Mass ◽  
Thermal Mass ◽  
Heating And Cooling ◽  
R Value ◽  
The Impact

The building industry is striving for environmental friendly and energy efficient facility developments, as we have used most of our natural resources for comfortable living. Therefore energy efficient houses are very significant to reduce energy consumption. Thermal mass can be used as one of the many techniques of energy efficiency in the housing industry. Thermal mass can store heat in it which can be released at a later time. This behaviour of thermal mass can play a significant role in heating and cooling energy consumption of houses. This study investigates the impact of thermal mass on heating and cooling energy performance of a detached house and a row attached house, which are two main types of housing in Canada. Energy Plus simulation software has been used in the study. Also the study includes two different climatic conditions in Canada, such as Toronto and Vancouver, to envision how thermal mass behaviour changes with climates. All these different studies show thermal mass has significant impact on reduced energy consumption (15% savings in Vancouver for CCHT house) and lowering indoor air temperature. Other strategies such as insulation high R value, increased south face glazing and reduced glazing U value have been integrated with thermal mass to see energy performance in both climates. It hows more energy reduction than only thermal mass strategy. For instance, in CCHT house insulation high R value with concrete high mass reduces maximum 27% of total energy for Vancouver location.

Methods for Improving Energy Performance of Single-family Buildings in Poland’s Climatic Conditions

2017 ◽  
Author(s):  
Hanna Jędrzejuk ◽  
Maciej Jaworski ◽  
Michał Chwieduk
Keyword(s):  
Thermal Performance ◽  
Ventilation System ◽  
Internal Heat ◽  
Energy Performance ◽  
High Heat ◽  
Climatic Conditions ◽  
Building Envelope ◽  
Single Family ◽  
Forced Ventilation ◽  
Climate Conditions

The effect of standard means of thermal upgrading of buildings on energy performance indices is studied in the paper. The following was considered: improving thermal performance of the envelope (walls, roof, floors over unheated cellars or ground-floor slabs, windows, and doors); using exterior blinds during heating and cooling seasons; using heat recovery (recuperation) in a forced ventilation system; reducing the ventilation air flow rate; and improving air-tightness of a building. The calculations were performed for a number of variants. Seven locations in Poland were selected based on outdoor climate conditions. Various standards of thermal performance of the building envelope, internal heat capacities, and ventilation rates were applied. Variations in internal heat gains, depending on the presence of occupants (heat gains from occupants and from lighting) were considered. Due to a dynamic nature of the energy processes that take place in a building, the simplified hourly method 5R1C was used in calculations. It was verified whether single-family buildings constructed in a way that is typically found in Poland, i.e. buildings with very high heat capacity and equipped with a forced ventilation system, can meet more stringent energy performance requirements.

scholarly journals Investigating The Impact Of Thermal Mass Towards Energy Efficient Housing In Canada

2021 ◽  
Author(s):  
Tasnuva Ahmed
Keyword(s):  
Energy Consumption ◽  
Energy Efficient ◽  
Energy Performance ◽  
Climatic Conditions ◽  
Simulation Software ◽  
High Mass ◽  
Thermal Mass ◽  
Heating And Cooling ◽  
R Value ◽  
The Impact

The building industry is striving for environmental friendly and energy efficient facility developments, as we have used most of our natural resources for comfortable living. Therefore energy efficient houses are very significant to reduce energy consumption. Thermal mass can be used as one of the many techniques of energy efficiency in the housing industry. Thermal mass can store heat in it which can be released at a later time. This behaviour of thermal mass can play a significant role in heating and cooling energy consumption of houses. This study investigates the impact of thermal mass on heating and cooling energy performance of a detached house and a row attached house, which are two main types of housing in Canada. Energy Plus simulation software has been used in the study. Also the study includes two different climatic conditions in Canada, such as Toronto and Vancouver, to envision how thermal mass behaviour changes with climates. All these different studies show thermal mass has significant impact on reduced energy consumption (15% savings in Vancouver for CCHT house) and lowering indoor air temperature. Other strategies such as insulation high R value, increased south face glazing and reduced glazing U value have been integrated with thermal mass to see energy performance in both climates. It hows more energy reduction than only thermal mass strategy. For instance, in CCHT house insulation high R value with concrete high mass reduces maximum 27% of total energy for Vancouver location.

scholarly journals Thermal Assessment of a Novel Drywall System Insulated with VIPs

Energies ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2373 ◽  
Author(s):  
Ioannis Atsonios ◽  
Ioannis Mandilaras ◽  
Maria Founti
Keyword(s):  
Thermal Performance ◽  
Energy Performance ◽  
High Energy ◽  
Building Envelopes ◽  
Building Systems ◽  
Ca 50 ◽  
Metal Frame ◽  
Thermal Bridges ◽  
One Year ◽  
The Impact

Advanced building envelopes targeting high energy performance should combine high thermal performance with easy and fast installation. The combination of lightweight steel-framed building systems with vacuum insulation panels (VIPs) form an attractive solution toward this requirement. In the present study, a lightweight metal frame drywall building insulated with VIPs is constructed and experimentally/theoretically investigated, focusing on the impact of every type of thermal bridges on the thermal performance of the envelope and its upgrade due to the presence of the VIPs at the walls. Temperature measurements obtained at several locations of the envelope, over a period of one year, are presented and analyzed. The results are in agreement with the theoretical values and demonstrate that the VIPs can reduce the thermal transmittance of the central part of the wall by ca. 50%, limiting the impact of metal studs. The paper discusses the impact of dimensional inaccuracies and damaged panels on the thermal performance of the envelope. It is shown that VIP decreases the impact of thermal bridges and reduces the risk of condensation inside the walls.

scholarly journals Use of Dissimilar Walling Systems on Residential Building Envelopes for Improving Their Thermal Performance

2009 ◽  
Vol 4 (2) ◽  
pp. 107-125
Author(s):  
Katherine Gregory ◽  
Behdad Moghtaderi ◽  
Adrian Page
Keyword(s):  
Energy Consumption ◽  
Thermal Performance ◽  
Residential Building ◽  
Climatic Conditions ◽  
Building Envelope ◽  
Thermal Mass ◽  
Building Envelopes ◽  
Numerical Predictions ◽  
Brick Veneer ◽  
East And West

This paper summarises the results of a combined numerical, statistical and experimental study concerned with the use of dissimilar walling systems on the external parts of a given building envelope. The rational behind this “hybrid wall” concept, as opposed to conventional approaches where identical walls are used in a building envelope, is to achieve a more effective distribution of thermal mass across the envelope and, hence, improve the overall thermal performance of the building. The effectiveness of the “hybrid wall” concept was investigated using a series of hypothetical building modules of common Australian residential constructions, namely Light Weight (LW), Brick Veneer (BV), Reverse Brick Veneer (RBV) and Cavity Brick (CB). These designs were examined numerically using a commercial energy rating tool known as “AccuRate”, statistically using JMP software and experimentally using a novel bench-scale setup developed as part of this study. The performance of each design was evaluated by its energy consumption. The numerical predictions and experimental data highlighted that the east and west walls have the most impact on the energy consumption under Australian climatic conditions. It was found that considerable reductions in the energy consumption could be achieved in cases where the hybrid wall concept was implemented through the use of high thermal mass insulated walls on the east and west sides of the building envelope.

Impact of roof shading on building energy performance in warm & humid climatic places of India

2020 ◽  
pp. 50-64
Author(s):  
Kuladeep Kumar Sadevi ◽  
Avlokita Agrawal
Keyword(s):  
Energy Consumption ◽  
Energy Conservation ◽  
Energy Performance ◽  
General Assumption ◽  
Climatic Conditions ◽  
Building Envelope ◽  
Passive Cooling ◽  
Base Case ◽  
U Value ◽  
The Impact

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.

THE GREEN ROOF THERMAL PERFORMANCE EVALUATION IN COMPARISON TO ASBESTOS CEMENT TILES APPLIED TO LIGHT STEEL FRAME BRAZILIAN BUILDINGS

2018 ◽  
Vol 12 (3) ◽  
pp. 288
Author(s):  
Angélica Felicidade Guião Marcato Costa ◽  
João Alexandre Paschoalin Filho ◽  
Tatiana Tucunduva Philipi Cortese ◽  
Brenda Chaves Coelho Leite
Keyword(s):  
Performance Evaluation ◽  
Relative Humidity ◽  
Heat Flow ◽  
Thermal Performance ◽  
Green Roof ◽  
Steel Frame ◽  
Internal Temperature ◽  
Green Cover ◽  
Asbestos Cement ◽  
Data Representative

This research aimed at comparing the thermal performance provided in experimental modules, one of which was performed with conventional cover, made of asbestos cement tiles; an another with green cover. The structure of the studied modules was executed using Light Steel Frame technique. As an experimental research, modules were built in a wide place, without the interference of shading. Instruments were installed in the inner part of the modules to measure the following data: air temperature, relative humidity. From the collected data, representative episodes have been chosen for the studies that aimed to compare the comfort provided by both modules, built with different roofs. As result, it was verified that the module with green roof had better performance than the module covered with asbestos cement tile in all selected episodes. The module covered with green roof maintained lower internal temperature variation throughout the days, indicating that the green roof has characteristic thermal insulation, reducing the heat flow from the roof.

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