Hygrothermal performance of a new thermal aerogel-based render under distinct climatic conditions

Maia, Joana; Pedroso, Marco; Ramos, Nuno M. M.; Pereira, Pedro F.; Flores‐Colen, Inês; Gomes, M. Glória; Silva, L.

doi:10.1016/j.enbuild.2021.111001

Cited by 26 publications

(14 citation statements)

References 43 publications

(52 reference statements)

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“…For the numerical analyses in this paper, the software WUFI [ 33 ], version 3.4 was used. WUFI is recognized software for building physics applications and it has been used and verified in several previous studies to solve coupled one- and two-dimensional heat and moisture transport in multilayer wall systems with ACMs [ 3 , 21 , 23 , 29 ]. In Equations (2) and (3), the governing equations for heat and moisture transport are given:

where H (J) is enthalpy, T (°C) is temperature, λ (W/(m·K)) is thermal conductivity,

(J) is the evaporation enthalpy of water,

(kg/m·s·Pa) is water vapor permeability,

(−) is relative humidity,

(Pa) is saturation vapor pressure, W (kg/m 3 ) is moisture content, and

(kg/m·s) is the liquid conduction coefficient.…”

Section: Methodsmentioning

confidence: 99%

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Increasing Water Absorptivity of an Aerogel-Based Coating Mortar in Subsequent Wetting and Drying

Karim

Johansson

Kalagasidis

2022

Gels

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Aerogel-based coating mortars are energy-efficient composites with thermal conductivities of 30–50 mW/(m·K). They are useful when retrofitting uninsulated building envelopes, particularly in listed masonry buildings, as shown in studies. Meanwhile, the long-term reliability of their hygrothermal properties, typically declared after a single laboratory measurement, is not confirmed. To illustrate the latter and by combining experimental and numerical methods, this study shows that (1) the capillary water absorptivity of a commercially available aerogel-based coating mortar increases after repeated drying and wetting cycles, and (2) leads to a higher moisture content in a masonry wall. After the third cycle, the measured water absorption was more than five times higher than after the first one. Based on numerical simulations, the increasing capillary water absorptivity results in 36% higher relative humidity in the wall if the aerogel-based coating mortar is applied externally and exposed to driving rain. Future research should investigate the reasons behind the observed deviations in the capillary water absorptivity and whether it applies to other types of aerogel-based coating mortars.

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where H (J) is enthalpy, T (°C) is temperature, λ (W/(m·K)) is thermal conductivity,

(J) is the evaporation enthalpy of water,

(kg/m·s·Pa) is water vapor permeability,

(−) is relative humidity,

(Pa) is saturation vapor pressure, W (kg/m 3 ) is moisture content, and

(kg/m·s) is the liquid conduction coefficient.…”

Section: Methodsmentioning

confidence: 99%

“…Among the studies on ACMs, [ 17 , 18 , 19 , 20 , 21 , 22 , 23 ] reported results on A cap for different trial mixtures of ACMs. Here, pre-conditioned samples were measured only once, and their properties were declared after the first wetting cycle.…”

Section: Introductionmentioning

confidence: 99%

Increasing Water Absorptivity of an Aerogel-Based Coating Mortar in Subsequent Wetting and Drying

Karim

Johansson

Kalagasidis

2022

Gels

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“…This paper intends to discuss the long-term performance of aerogel cement-based rendering systems and contribute to the knowledge of the in-service performance of innovative solutions, complementing the hygrothermal performance analysis carried out by Maia et al [38]. As such, the present work has the objective of assessing the durability of a new aerogel cement-based rendering system exposed to distinct environmental conditions, such as freeze-thaw, humidification, and heat-cold accelerated degradation mechanisms.…”

Section: Introductionmentioning

confidence: 95%

Durability of a New Thermal Aerogel-Based Rendering System under Distinct Accelerated Aging Conditions

et al. 2021

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The widespread application of innovative thermal enhanced façade solutions requires an adequate durability evaluation. The present work intends to assess the durability of a new aerogel cement-based rendering system through the adaptation of different accelerated aging cycles, such as heating–freezing, freeze–thawing, and heat–cold. Several mechanical properties and also capillary and liquid water absorptions were tested for uncoated and coated specimens. A decrease in the mechanical strength, especially after freeze–thaw cycles, was observed. However, the water action promoted the late hydration of the cement paste contributing to the densification of the matrix and, consequently, the increase of the adhesive strength. Additionally, a decrease in the dynamic modulus of elasticity and an increase in the Poisson’s ratio were observed after aging, which indicates a higher capacity of the render to adapt to substrate movements, contributing to a reduction of cracking.

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“…E.g. Maia et al [27] investigated the hygrothermal performance of a new thermal aerogel-based render applied as a component of a multilayer coating system by measuring relevant material properties and conducting hygrothermal simulations. The study highlights the importance of applying a finishing coating with low capillary absorption to reduce the water content in the inner layer and consequently the impact on the U-value of the façade.…”

Section: Accelerated Artificial Ageing Of Faç Ade Systemsmentioning

confidence: 99%

Moisture Accumulation in Building Façades Exposed to Accelerated Artificial Climatic Ageing—A Complementary Analysis to NT Build 495

2021

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Building façades must endure severe climatic exposure throughout their lifetimes. To prevent damage and expensive repairs, ageing tests are used in durability assessments. The NT Build 495 describes an artificial ageing procedure to address building material and component resistance to ultraviolet (UV) light, heat, water, and frost using a climate simulator. The test has been used for decades to investigate exterior surface materials and façade products but has only recently been adopted for multi-layered systems. This study investigates moisture accumulation in a façade system for retrofitting based on concrete and thermal insulation. Hygrothermal simulations of the façade system subjected to ageing were conducted. Moisture accumulation was considered theoretically for the current test procedure and compared to a modified setup in which the interior climate was controlled at 21 °C. Physical measurements were performed in the climate simulator to determine the boundary conditions. Results showed that moisture accumulation in the thermal insulation was largely affected by the type of concrete, that applying a water-repellent surface treatment reduced moisture accumulation, and that the current setup resulted in less moisture accumulation compared to the modified setup. The latter implicates accelerated degradation with the modified setup.

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Hygrothermal performance of a new thermal aerogel-based render under distinct climatic conditions

Cited by 26 publications

References 43 publications

Increasing Water Absorptivity of an Aerogel-Based Coating Mortar in Subsequent Wetting and Drying

Increasing Water Absorptivity of an Aerogel-Based Coating Mortar in Subsequent Wetting and Drying

Durability of a New Thermal Aerogel-Based Rendering System under Distinct Accelerated Aging Conditions

Moisture Accumulation in Building Façades Exposed to Accelerated Artificial Climatic Ageing—A Complementary Analysis to NT Build 495

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