Hygrothermal Performance and Damage Risk of Green Roofs

Zirkelbach, Daniel; Schafaczek, B.; Künzel, Hartwig M.

doi:10.1007/978-3-642-31158-1_7

Cited by 6 publications

(8 citation statements)

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“…When the roofing system having a built-in-moisture, the corresponding results for the case of the initial moisture content corresponds to 90% RH are also shown in Figures 6C,D. For different values of the initial moisture content, Figure 6A through Figure 6D show that the conventional/black roof with α s = 0.88 shows lower moisture accumulation compared to the cool roof with α s = 0.05. This observation is in agreement with many previous studies (e.g., see Solecki et al, 2005;Bludau et al, 2009Bludau et al, , 2010Zirkelbach et al, 2010;Saber et al, 2011aSaber et al, , 2012a. As shown in Figures 6A,B for the case of initial relative (RH int ) of 50%, the moisture increases in all roofs from year-to-year during the first 5 years.…”

Section: Effect Of Rooftop Short-wave Absorption Coefficient On the Hsupporting

confidence: 92%

“…Conducting hygrothermal simulation for a roof, subjected to a climatic condition, requires a prior knowledge of the initial conditions (i.e., at time = 0) for both the temperature and moisture content distributions inside the roof. Normally, these initial conditions are not known and should be assumed (Bludau et al, 2009(Bludau et al, , 2010Zirkelbach et al, 2010;Saber et al, 2011aSaber et al, , 2012a. In this study, for each roof, time = 0.0 corresponded to January 1st at 12.00 a.m. at which the initial temperature in all material layers was assumed equal 10 • C. Also, the initial moisture content in all material layers was assumed to correspond to 50% RH (Saber et al, 2011a(Saber et al, , 2012a.…”

Section: Initial Conditions and Simulation Periodmentioning

confidence: 99%

“…Roofing systems are so much more than just protections from the rain and sun. Many investigators (Desjarlais, 1995;Desjarlais et al, 1998;Solecki et al, 2005;Jo et al, 2010;Oleson et al, 2010;Ray and Glicksman, 2010;Urban and Roth, 2010;Zirkelbach et al, 2010;Bentz, 2011;Durhman et al, 2011;Ismail et al, 2011;McHugh and Petrick, 2011;Xu et al, 2012;Hutchinson, 2017) have shown that white (cool) and green roofing systems can reduce the operating energy loads of buildings and as well help reduce greenhouse gas emissions. Bentz (2011) explored decision-making process for green options in reroofing systems.…”

Section: Introductionmentioning

confidence: 99%

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Hygrothermal Performance of Cool Roofs Subjected to Saudi Climates

2019

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In regions with hot climatic conditions such as that in Saudi Arabia, a substantial share of energy is used for cooling the buildings. Many studies have shown that cool (white) roofs can help reduce the cooling energy load and thus the demand for energy over time. Also, cool roofs help reduce the urban heat island during the summer time. This research study focused on determining: (a) whether cool roofs lead to risk of condensation and mold growth in Saudi climates, (b) the amount of energy savings as result of using cool roofs instead of black roofs of same insulation amount, and (c) the reduction in the amount of insulation in cool roof having the same energy performance level as the black roof. As such, numerical simulations were conducted for a roofing system that is commonly used in low-rise buildings in Saudi Arabia in order to asses and compare the energy and hygrothermal performance of cool and black roofs. The roof was subjected to weather conditions of the Eastern Province of Saudi Arabia. The indoor conditions were taken based simple method of ASHRAE Standard 160. The results showed no moisture accumulation occurred from year-to-year after 6 years and 7 years for the black roof and cool roof, respectively, and the highest relative humidities in the black and cool roofs were well below 80% resulting in no risk of condensation and mold growth occurred in these roofs. The main outcome of this study has shown the capabilities of using reflective materials with different shortwave solar absorption coefficients for enhancing the energy performance of roofs and/or reducing the amount of insulation that resulted in same energy performance as black roofs. This study can be used in future for upgrading the Saudi Building Code so as to allow less roof insulation if cool roof is installed.

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Section: Effect Of Rooftop Short-wave Absorption Coefficient On the Hsupporting

confidence: 92%

Section: Initial Conditions and Simulation Periodmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hygrothermal Performance of Cool Roofs Subjected to Saudi Climates

2019

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“…Many previous studies [4,[48][49][50][51][52][53][54][55][56][57] including this current study have shown that green and reflective roofs are not only protection from solar radiation and rain but can save energy, mitigate urban heat islands, decrease greenhouse gas emissions, and reduce local air pollution while increasing the thermal comfort level (i.e., indoor air quality). The reflective roofs are widely known in the markets as white roofs and cool roofs.…”

Section: White Roofing Systems Cost-benefitsmentioning

confidence: 83%

Review of White Roofing Materials and Emerging Economies with Focus on Energy Performance Cost-Benefit, Maintenance, and Consumer Indifference

2021

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This article performed a comprehensive review of the different state-of-the-art of roofing technologies and roofing materials and their impact on the urban heat island (UHI) and energy consumption of buildings. The building roofs are the main sources of undesirable heat for buildings, especially in warm climates. This paper discusses the use and application of white roofing material in emerging economies. The use of white roofing material is a suggestion because of its cooling, evaporative and efficiency characteristics compared to traditional black roofing materials. Many research studies have shown that the darker roofing surfaces that are prevalent in many urban areas actually can increase temperature by 1 to 3 degrees Celsius to the environment surrounding these urban areas. Additionally, improved temperature control and heat reflection also work to reduce the energy requirements for the interior spaces of the structures that have white roofing surfaces. The white or lighter colored roofs tend to reflect a part of the solar radiation that strikes the roof’s surface. Consequently, one might believe that white roofing material would be commonplace and especially so within emerging economies. Yet, this is hardly the case at all. This paper examines the issue of white roofing materials in emerging economies from a dual perspective. The dual perspective includes the technical details of white roofing material and its impact on lowering the interior temperature of the affected structures, which consequently reduces hours of indoor thermal discomfort and use of air conditioners in indoor spaces. The other element in this study, however, involves the marketing aspect of white roofing material. This includes its adoption, acceptance and cost-benefit in emerging economies.

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“…Many investigators [1][2][4][5][6][7][8][9][10][11][12][13][14][15] have shown that green and reflective roofs can save energy, mitigate urban heat islands, slow global warming by decreasing greenhouse gas emissions, and reduce local air pollution while increasing thermal comfort. The effects of globally installing white roofs were assessed using an urban canyon model coupled to a global climate model [10].…”

Section: Introductionmentioning

confidence: 99%

Impact of reflective roofs on the overall energy savings of whole buildings

2020

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Many previous studies by the authors of this paper and others have shown that installing white/reflective/cool roofing systems resulted in energy savings. The amount of energy savings depended on the longwave thermal emissivity and the short-wave solar reflectivity of the rooftop surfaces. The question is “what is the percentage energy savings for the whole building as a result of using cool roofing systems instead of conventional/black roofing systems? To answer this question, three-dimensional energy simulations are conducted for typical Saudi buildings when they are subjected to the natural weathering conditions of the Eastern Province of Saudi Arabia. Several Window-to-Wall Ratios (WWRs) having different thermal resistances (R-values) and Solar Heat Gain Coefficients (SHGCs) are considered in the study. The windows are located in the different main solar orientations. To investigate the effect of the area ratio of the roof to the walls on the potential energy saving due to using cool roofs, one storey and two-storey are considered in this study. Results showed that using reflective materials with lower short-wave solar absorption coefficients in the roofing systems have resulted in a decrease in the yearly total energy loads of one-storey building and two-storey building.

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Hygrothermal Performance and Damage Risk of Green Roofs

Cited by 6 publications

References 0 publications

Hygrothermal Performance of Cool Roofs Subjected to Saudi Climates

Hygrothermal Performance of Cool Roofs Subjected to Saudi Climates

Review of White Roofing Materials and Emerging Economies with Focus on Energy Performance Cost-Benefit, Maintenance, and Consumer Indifference

Impact of reflective roofs on the overall energy savings of whole buildings

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