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

Saber, Hamed H.

doi:10.1016/j.buildenv.2013.04.009

Cited by 11 publications

(41 citation statements)

References 14 publications

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“…Measurements on various types of roof installations using reflective insulation have been conducted (Belusko et al [7], Miranville et al [53], Muselli [57], Saber [67], Saber [68], Suehrcke et al [70]). Some of these studies also attempt to give an experimental evaluation of performances from field measurements.…”

Section: Roofsmentioning

confidence: 99%

Low-emissivity materials for building applications: A state-of-the-art review and future research perspectives

Jelle

Kalnæs

Gao

2015

Energy and Buildings

229

100

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Low-emissivity (low-e) materials can be used in order to reduce energy usage in both opaque and transparent areas of a building. The main focus for low-e materials is to reduce the heat transfer through thermal radiation. Furthermore, low-e materials will also influence on the daylight and total solar radiation energy throughput in windows, the latter one often characterized as the solar heat gain coefficient (SHGC). This work reviews low-e materials and products found on the market, and their possible implementations and benefits when used in buildings. The SHGC is often left out by many countries in energy labellings of windows. With opaque materials, research is still ongoing to correctly calculate the effect with regard to thermal performance when applied in buildings. Future research perspectives on where low-e technologies may develop are explored. To the authors' knowledge, there seems to be little available literature on how ageing affects low-e materials and products. As this is of large significance when calculating energy usage over the lifetime of a building, ageing effects of low-e materials should be addressed by manufacturers and the scientific community.

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Section: Roofsmentioning

confidence: 99%

Low-emissivity materials for building applications: A state-of-the-art review and future research perspectives

Jelle

Kalnæs

Gao

2015

Energy and Buildings

229

100

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“…Unlike the R-values provided in ASHRAE table (2017), the results of those studies showed that the aspect ratios of the enclosed airspaces can have significant effects on their R-values (Saber, 2013a(Saber, , 2013b(Saber, , 2013c(Saber, , 2014a(Saber, , 2014b. In some of the studies (Saber, 2013a(Saber, , 2013b(Saber, , 2013c(Saber, , 2014a(Saber, , 2014b, considerations were given to investigate the potential increase in the R-value of the enclosed airspace when a thin sheet having different values of emissivity on both sides was placed in the middle of the airspace as shown in Figure 4(b). As will be shown later, the results showed that, depending on the value of the effective emittance, thickness of the airspace, orientation of the airspace, and direction of heat flow, the R-value could be easily doubled and in some cases could be tripled by incorporating this thin sheet along the middle of the enclosed airspace.…”

Section: Overview Of Thermal Performance Of Enclosed Spacesmentioning

confidence: 88%

“…It is important to accurately determine the effective R-values of the enclosed spaces of different dimensions, effective emittances, inclination angles, directions of heat flow, mean airspace temperatures, and temperature differences across the airspaces (Tariku and Iffa, 2017). Many studies were conducted to determine the R-values of RI products and low-e coatings in IGUs, and wall and roofing systems incorporating RI products (Craven and Garber-Slaght, 2011;Desjarlais and Tye, 1990;Desjarlais and Yarbrough, 1991;D'Orazio et al, 2012;Escudero et al, 2013;European Commission, 2010;Fairey, 1985;Fricker and Yarbrough, 2011;Glicksman, 1991;Gross and Miller, 1989;Han et al, 1986;IEA, 1987;Kahsay et al, 2019;Laouadi et al, 2013;Medina, 2000;Saber, 2012Saber, , 2013aSaber, , 2013bSaber, , 2013cSaber, , 2013dSaber, , 2014aSaber, , 2014bSaber et al, 2011aSaber et al, , 2011bSaber et al, , 2012aSaber et al, , 2012bSaber et al, , 2013Saber and Laouadi, 2011;Saber and Maref, 2012;Saber and Swinton, 2010;Tariku and Iffa, 2017;Tenpierik and Hasselaar, 2013;Vrachopoulos et al, 2012;Yarbrough, 1983). Also, there are many claims indicating that RI products can have high thermal resistance.…”

Section: Overview Of Thermal Performance Of Enclosed Spacesmentioning

confidence: 99%

“…A number of previous studies (Saber, 2013a(Saber, , 2013b(Saber, , 2013c(Saber, , 2014a(Saber, , 2014b were focused on predicting the thermal performance and the effective R-values of vertical enclosed airspaces (Tenpierik and Hasselaar, 2013), horizontal enclosed airspaces with upward heat flow (Saber, 2013c), horizontal enclosed airspaces with downward heat flow (Saber, 2014a), high-sloped (45°) enclosed airspaces with downward heat flow (Saber, 2013b), and low-sloped (30°) enclosed airspaces with downward heat flow (Saber, 2014b), for a wide range of thickness, aspect ratio, mean temperature, temperature differential, effective emittance, and direction of heat flow. Unlike the R-values provided in ASHRAE table (2017), the results of those studies showed that the aspect ratios of the enclosed airspaces can have significant effects on their R-values (Saber, 2013a(Saber, , 2013b(Saber, , 2013c(Saber, , 2014a(Saber, , 2014b. In some of the studies (Saber, 2013a(Saber, , 2013b(Saber, , 2013c(Saber, , 2014a(Saber, , 2014b, considerations were given to investigate the potential increase in the R-value of the enclosed airspace when a thin sheet having different values of emissivity on both sides was placed in the middle of the airspace as shown in Figure 4(b).…”

Section: Overview Of Thermal Performance Of Enclosed Spacesmentioning

confidence: 99%

“…For enclosed airspace of length 305 mm and different T avg , DT, and e eff , the results showed that both predicted and ASHRAE R-values were within +2.6% and -4.2% for d = 13 mm, +2.3% and -6.0% for d = 20 mm, +12.1% and -7.6% for d = 40 mm, and +42.6% and -13.4% for d = 90 mm (Saber, 2013c). For 45°sloped enclosed airspaces with downward heat flow condition of different H, d, T avg , DT, and e eff , the predicted R-values were compared with ASHRAE R-values (Saber, 2013b). For enclosed airspace of length 305 mm and different T avg , DT, and e eff , the results showed that the absolute percentages of the maximum deviations between the predicted and ASHRAE R-values were 9.5%, 32.4%, 55.1%, and 42.0%, respectively, for enclosed airspace thickness of 13, 20, 40, and 90 mm.…”

Section: Model Descriptions and Validationmentioning

confidence: 99%

See 2 more Smart Citations

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

Saber

Maref

Hajiah

2019

Journal of Building Physics

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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.

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Overview of Thermal Performance of Air Cavities and Reflective Insulations

Saber

2022

Thermal Insulation and Radiation Control Technologies for Buildings

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

Cited by 11 publications

References 14 publications

Low-emissivity materials for building applications: A state-of-the-art review and future research perspectives

Low-emissivity materials for building applications: A state-of-the-art review and future research perspectives

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

Overview of Thermal Performance of Air Cavities and Reflective Insulations

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