Steady-state and transient thermal measurements of green roof substrates

Pianella, Andrea; Clarke, Robin E; Williams, Nicholas S.G.; Chen, Dong; Aye, Lu

doi:10.1016/j.enbuild.2016.09.024

Cited by 43 publications

(34 citation statements)

References 39 publications

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“…Similarly, heat flux ( Figure 8) differences were more evident on sunny days, but did not have a clear pattern. Due to the limitations of the soil outputs, which we have already explained, the parametric analysis does not fully reveal the importance of the CDS for the green roof thermal performance as shown in previous studies [21,39,41]. Surprisingly, there was little effect of varying the design parameter substrate thickness (ST) as simulation results were consistent for all values, except on two dry days (i.e., Hours 73-96 and 210-225 [40]) where the thickest simulated extensive green roof substrate (ST = 0.30 m) had cooler temperatures than the other values.…”

Section: Parametric Analysismentioning

confidence: 99%

“…Similarly, heat flux (Figure 8) differences were more evident on sunny days, but did not have a clear pattern. Due to the limitations of the soil outputs, which we have already explained, the parametric analysis does not fully reveal the importance of the CDS for the green roof thermal performance as shown in previous studies [21,39,41]. Finally, the operational parameter soil moisture content (MC) showed small differences (~2 • C) in the temperature peaks on sunny days (i.e., Hours 169-192 [40]).…”

Section: Parametric Analysismentioning

confidence: 99%

“…While the extra dead load would be negligible for commercial buildings, this is not the case for most of Melbourne's low-rise residential Although the 200 mm green roof gives the best thermal performance, it has an analogous performance to the 150 mm green roof when unirrigated and unvegetated, and there is a small difference when it is irrigated and sparsely vegetated, but it is considerably heavier in weight. The 150 mm green roof with the scoria mixture substrate has a dead load of~2 kN m −2 versus the 200 mm green roof which is~2.5 kN m −2 [41,42]. Under this circumstance, a 50 mm shallower scoria substrate would have less weight (between 0.466 (dry) and 0.554 (saturated) kN m −2 ) and would be a more viable option to retrofit to a wider range of existing buildings.…”

Section: Summer Heat Fluxes Of Sparsely Vegetated Green Roofsmentioning

confidence: 99%

“…While the extra dead load would be negligible for commercial buildings, this is not the case for most of Melbourne's low-rise residential buildings which have modest weight loading capacity [43]. If an alternative substrate were used, such as crushed roof tile [41,44], total load would increase up to~3.15 kN m −2 , and it would be even more difficult to retrofit a residential building with a green roof [45].…”

Section: Summer Heat Fluxes Of Sparsely Vegetated Green Roofsmentioning

confidence: 99%

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Substrate Depth, Vegetation and Irrigation Affect Green Roof Thermal Performance in a Mediterranean Type Climate

et al. 2017

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Green roofs are consistently being used to reduce some of the negative environmental impacts of cities. The increasing interest in extensive green roofs requires refined studies on their design and operation, and on the effects of their relevant parameters on green roof thermal performance. The effects of two design parameters, substrate thickness (ST) and conductivity of dry soil (CDS), and four operating parameters, leaf area index (LAI), leaf reflectivity (LR), stomatal resistance (SR), and moisture content (MC), were investigated using the green roof computer model developed by Sailor in 2008. The computer simulations showed that among the operating parameters, LAI has the largest effects on thermal performance while CDS is a more influential design parameter than ST. Experimental investigations of non-vegetated and sparsely vegetated green roofs in Melbourne were principally used to understand the effect of the substrate and enable better understanding of dominant heat transfer mechanisms involved. Investigated green roofs had three substrate thicknesses (100, 150 and 200 mm), and their performance was compared to a bare conventional roof. In contrast to the computer simulations, the experimental results for summer and winter showed the importance of MC and ST in reducing the substrate temperature and heat flux through the green roof.

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Section: Parametric Analysismentioning

confidence: 99%

“…Similarly, heat flux (Figure 8) differences were more evident on sunny days, but did not have a clear pattern. Due to the limitations of the soil outputs, which we have already explained, the parametric analysis does not fully reveal the importance of the CDS for the green roof thermal performance as shown in previous studies [21,39,41]. Finally, the operational parameter soil moisture content (MC) showed small differences (~2 • C) in the temperature peaks on sunny days (i.e., Hours 169-192 [40]).…”

Section: Parametric Analysismentioning

confidence: 99%

Section: Summer Heat Fluxes Of Sparsely Vegetated Green Roofsmentioning

confidence: 99%

Section: Summer Heat Fluxes Of Sparsely Vegetated Green Roofsmentioning

confidence: 99%

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Substrate Depth, Vegetation and Irrigation Affect Green Roof Thermal Performance in a Mediterranean Type Climate

et al. 2017

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“…The specific objectives were, first, to characterize a set of five green roof substrates in terms of their hydrodynamic and thermal properties: water retention curve, hydraulic conductivity curve, thermal conductivity, and specific heat capacity. The substrates investigated had organic matter contents that ranged between 4 and 35% and were chosen due to their common use in green roofs (Pianella et al, 2016; Zhao et al, 2014) and their local availability. Secondly, we aimed to evaluate the impacts of these properties on water and heat transport through the green roof substrates using numerical simulations and including the effect of irrigation or drainage.…”

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confidence: 99%

Porous Media Characterization to Simulate Water and Heat Transport through Green Roof Substrates

Sandoval

Bonilla

Gironás

et al. 2017

Vadose Zone Journal

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Core Ideas Hydrodynamic and thermal properties of five green roof substrates were determined. Coupled heat and water transport in a hypothetical roof was simulated. The green roof substrates showed a large capacity to store and transport water. Water retention, storage, and organic matter control substrate hydraulic behavior. Green roofs integrate vegetation into buildings, thereby minimizing energy requirements and water runoff. An understanding of the processes controlling water and heat fluxes in green roofs under site‐specific climatic conditions is needed to optimize their benefits. The hydrodynamic and thermal characteristics of substrates and vegetation layers are the primary controlling factors determining water and heat fluxes on green roofs. We characterized the physical, hydrodynamic, and thermal properties of five green roof substrates. We performed coupled heat and water transport numerical simulations to assess the impact of these properties on the hydraulic and thermal performance of a hypothetical roof system. The five substrates showed a large capacity to store and transport water, while their ability to conduct heat was similar to other green roof substrates. Under unsaturated conditions, water retention, storage capacity, and organic matter (OM) content of the substrates controlled the hydraulic and thermal response of each substrate. Our simulation results show that the substrate with the best capacity to store water and to reduce the heat flux through the substrate layer was composed of perlite and peat and had large OM content (30.7%) and saturated water content (0.757 cm3 cm−3). This substrate outperformed the others, probably due to its low thermal conductivity and its large pore space. The dynamic modeling presented in this study can represent the complexity of the processes that are occurring in green roof substrates, and thus it is a tool that can be used to design the configuration of a green roof.

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A Novel Laboratory Procedure to Determine Thermal Conductivity of Green Roof Substrates

Cascone

Gagliano

2023

Sustainability in Energy and Buildings 2022

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Steady-state and transient thermal measurements of green roof substrates

Cited by 43 publications

References 39 publications

Substrate Depth, Vegetation and Irrigation Affect Green Roof Thermal Performance in a Mediterranean Type Climate

Substrate Depth, Vegetation and Irrigation Affect Green Roof Thermal Performance in a Mediterranean Type Climate

Porous Media Characterization to Simulate Water and Heat Transport through Green Roof Substrates

A Novel Laboratory Procedure to Determine Thermal Conductivity of Green Roof Substrates

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