Façade
A theoretical Model of Natural Ventilation Enhanced by Solar Thermal Energy in a Double-skin Façade
Authors: Y., Tao, Y. Yan, M.Y.L. Chew, J. Tu, L. Shi
Source: Energy, 276, 2023.
https://doi.org/10.1016/j.energy.2023.127534
Abstract:
Compared to previous theoretical analysis of naturally ventilated double-skin façade (NVDSF), still in scarcity is a model that can reflect the coupling mechanism of radiation and natural convection, meanwhile being readily calculable to save from excessive numerical computing. Therefore, this study proposes a new theoretical model for an NVDSF that addresses its thermal and ventilation performance under varying environmental conditions. The theoretical analysis of energy balance and buoyancy flow is deepened by additional numerical modelling that reveals features of the coupled heat transfer and fluid flow. Key correlations between radiation and natural convection obtained from simulation data assisted in establishing an explicit solution of glazing temperatures, which are consequently used to moderate the fully mixed model for obtaining the natural ventilation rate. Eventually, the new theoretical model is featured with a more accurate evaluation of channel natural convection and straightforward calculation of temperature and flow rates in response to external conditions. In addition, an example performed over a daily condition demonstrates the capability of the theoretical model to replace time-consuming numerical simulations over transient changes. The in-depth understanding of the solar-assisted natural ventilation mechanisms revealed by this model can contribute mainly to facilitating similar passive energy-saving techniques that involve solar radiation absorption in glazing materials.
Keywords: Renewable energy, Natural ventilation, Double-skin facade, Theoretical model, CFD modelling
Predicting airlow in naturally ventilated double-skin facades: theoretical analysis and modelling
Authors: Yao Tao, Xiang Fang, Michael Yit Lin Chew, Lihai Zhang, Jiyuan Tu, Long Shi
Source: Renewable Energy, Volume 179, December 2021, Pages 1940-1954
https://doi.org/10.1016/j.renene.2021.07.135
Abstract:
Naturally ventilated double skin façade (NVDSF) utilizes solar radiation to introduce natural ventilation through a double-skin façade cavity with vents. It is an easy-to-implement green technology that can be widely applied to new or existing buildings. However, its implementation in buildings is still limited as the coupled radiation and natural convection pose challenges in predicting ventilation performance. Moreover, the diversity of real-life applications raises a great need for a universally applicable method that can account for realistic design factors. Hence, an in-depth theoretical analysis model is required to facilitate the application of NVDSFs in buildings. This study proposes two new analytical models for NVDSFs that can directly predict ventilation rates with simple inputs. Numerical simulations are also conducted to validate the developed analytical models. It demonstrated that the experimentally validated numerical model can offer accurate predictions of natural convection and radiation for the case that involved complicated environmental, structural, and material factors. Most importantly, the realistic scenarios, NVDSFs with exterior vent louvers are studied both analytically and numerically. Different optical properties from two glazing materials, regular glass and low-e glass, are also tested with the proposed analytical models. Through validation, the discrepancies of the predictions by the proposed analytical models are −5% to −9% for ‘no-louver’ NVDSF for two different glazing materials (i.e., regular and low-e glass), and 13%–27% for NVDSFs with adjustable louver angles 45°–150°.
Climate Change Projection and its Impacts on Building Façade in Singapore
Authors: Lup Wai Chew, Xian-Xiang Li, M.Y.L. Chew
Source: Sustainability 2023, 15(4), 3156; https://doi.org/10.3390/su15043156
Abstract:
Singapore is one of the most populous countries, and the majority of the population stays in high-rise public flats. In 2021, there were about 1.1 million public residential units, of which 79% were above 20 years old. The number of incidents of falling objects from a height has been increasing due to the aging and deterioration of buildings. The Periodic Façade Inspection (PFI) regime was enacted in 2020 to mandate façade inspections for all buildings above 13 m and exceeding 20 years old. However, the relatively new PFI regime has not considered the potential impacts of climate change on building façades. In this paper, the common root causes of façade defects that can be impacted by climate change are first identified. Based on the climate projection in Singapore to 2100, Singapore is expected to experience a higher mean temperature, a higher rainfall intensity, more extreme rainfall events, and a higher wind gust speed. Overall, these changes in the climate pattern will accelerate corrosion or degradation, material fatigue, adhesion failure, biological attack, and humidity or dampness. The impacts of climate change on vertical greeneries are also discussed. This paper provides a first insight into the key concerns to focus on for the future revision and improvement of the PFI regime to incorporate climate change impacts on façades.
Keywords: climate change; façade inspection; falling objects; building maintenance; facility management; public safety
Long-Standing Themes and Future Prospects for Inspection and Maintenance of Façade Falling Objects from Tall Buildings
Authors: Michael Y.L. Chew, Vincent J.L. Gan
Source: Sensors 2022, 22(16), 6070; https://doi.org/10.3390/s22166070
Abstract:
The increasing number of accidents arising from falling objects from the façade of tall buildings has attracted much attention globally. To regulators, a preventive approach based on a mandatory periodic façade inspection has been deemed as a necessary measure to maintain the functionality and integrity of the façade of tall buildings. Researchers worldwide have been working towards a predictive approach to allow for the assessment of the likely failure during some future period, by measuring the condition of the façade to detect latent defects and anomalies. The methods proposed include laser scanning, image-based sensing and infrared thermography to support the automatic façade visual inspection. This paper aims to review and analyse the state-of-the-art literature on the automated inspection of building façades, with emphasis on the detection and maintenance management of latent defects and anomalies for falling objects from tall buildings. A step-by-step holistic method is leveraged to retrieve the available literature from databases, followed by the analyses of relevant articles in different long-standing research themes. The types and characteristics of façade falling objects, legislations, practices and the effectiveness of various inspection techniques are discussed. Various diagnostic, inspection and analytical methods which support façade inspection and maintenance are analysed with discussion on the potential future research in this field.
Keywords: automated inspection; building façade; laser scanning; computer vision; deep learning; 3D reconstruction; information modelling; design optimisation
A review of factors affecting delamination inspection by passive infrared thermography for infrastructures
Authors: Ko Tomita and Michael Yit Lin Chew
Source: Sensors 2022, 22(2), 423; https://doi.org/10.3390/s22020423
Abstract:
This paper provides a comprehensive review on the use of infrared thermography to detect delamination on infrastructures and buildings. Approximately 200 pieces of relevant literature were evaluated, and their findings were summarized. The factors affecting the accuracy and detectability of infrared thermography were consolidated and discussed. Necessary measures to effectively capture latent defects at the early stage of delamination before crack formation were investigated. The results of this study could be used as the benchmarks for setting standardized testing criteria as well as for comparison of results for future works on the use of infrared thermography for detection of delamination on infrastructures and buildings.
Keywords: infrared thermography; delamination; building; infrastructure; time window; environment; infrared camera; target object; thermal property
A study on the effectiveness of biological growth resistant coatings on external building façade systems in the tropics
Authors: Ashan Senel Asmone, Michael Yit Lin Chew
Source: Journal of Building Engineering, Volume 31, September 2020, 101377
Abstract:
Traditional façade cleaning processes can be dangerous, labour-intensive, and impairs the ease of façade maintenance. Thus, in improving the maintainability of the façade systems, facility managers search for novel strategies to reduce the cleaning cycles. Façade systems in tropical cities are frequently and severely affected by biological attacks such as algae. However, there is a considerable dearth of knowledge on the effectiveness of novel façade coating systems; proposed to prevent biological growth in tropical buildings. As part of an on-going effort to create a material manual, the effectiveness of six commercially available façade coating products on three different substrates (granite, aluminium, rendering materials), of a building under Singapore’s tropical conditions to inhibit biological growth is evaluated.
On-site photogrammetric data were collected over six months to analyse using an updated novel digital image processing procedure to evaluate the development of biological growth on the façade. A lifecycle cost (LCC) analysis is carried out for each type of façade coating application. The analysis from site measurements showed that all products exhibited improved performance on keeping the surfaces cleaner than the untreated façade surfaces. As the level of improvement varied between different substrates, a façade cleaning index is defined for each coating system. A lifecycle cost analysis showed varying results on the improvement in the performance of the products applied. A general reduction in cleaning cycles favours the facility’s operating costs for granite and aluminium substrates. For rendering materials, the high cost associated with the application appeared to make the LCC less attractive.
A Technical Evaluation Index for Curtain Wall and Cladding Façades
Authors: M.Y.L.Chew, Shan Shan Tan, Kang Kok Hin
Source: Structural Survey, Construction and Building Materials, Volume 22, Number 4, 2004, pp. 210-227.
Abstract:
An assessment framework derived from face-to-face interviews with building managers and comprehensive condition surveys of commercial buildings is proposed. Twenty-eight parameters are identified and tested for significance in affecting the technical evaluation score for curtain wall and cladding façades. The proposed framework is intended as a practical benchmark to assess and document the existing condition of the façade and further assist in the proper management of the maintenance strategy of the façade throughout its whole service life.
Keywords: Maintenance, Performance monitoring, Walls, Cladding
A Neural Network Approach to Assessing Building Façade Maintainability in the Tropics
Author: M.Y.L. Chew, Nayanthara De Silva And Shan Shan Tan
Sources: Construction Management and Economics, Volume 22, Number 6, 2003, pp. 581-594.
Abstract:
A model was developed to assess the maintainability of façade using neural network techniques. Inputs were derived from comprehensive studies of 570 tall buildings (more than 12 stories) through detailed field evaluation and interviews with professionals in the whole building delivery process. Sensitivity analysis showed that the most significant factors associated with façade maintainability include the system selection, detailing, accessibility and material performance.
Keywords: Maintainability, façade, risk, building defect, neural network, sensitivity analysis
Staining Arising from Design Features
Authors: M.Y.L.Chew, Phay Ping Tan
Source: Construction and Building Materials, Volume 17, Number 3, 2003, pp. 181-187 .
Abstract:
The rain run-off flow pattern over some main façade design features of impermeable materials was investigated by conducting simulations over them. The relationship between runoff flow pattern and the observed staining patterns were evaluated. Four main design features namely ledges, joints misalignment, protruding fixtures, and louver units were identified. The formation of stains was observed to be irregular and was determinable by the runoff flow and the dirt build-up on the façade.
Keywords: Flow pattern, Staining patterns, façade staining, Design features
Factorial Method for Performance Assessment of Building façades
Authors: M.Y.L.Chew, Nayanthara De Silva
Source: journal of Construction Engineering and Management, Volume 130, Number 4, 2003, pp. 525-533.
Abstract:
A methodology for assessing the performance of building façades based on the risk of defect occurrence was developed. The methodology relies on the accurate prediction of ~1! the frequency of the occurrence of various types of defects over time based on historical data ~30 years!, and ~2! the significance of the occurrence of various types of defects to the specific performances anticipated by the users. The proposed methodology can be used for the evaluation of the maintainability and whole life performance of a building right from the planning stage.
Factors Affecting Ceramic Tile Adhesion for External Cladding
Authors: M.Y.L.Chew
Source: Structural Survey : Volume 13, Number 5, 1999, pp. 293-296
Abstract:
The effect of the exposure temperature during and after the application of a tiling system on the development of bond strength of the adhesive was evaluated. It was shown that adhesive with approximately 50% of the water replaced by a polymer latex has the most consistent performance in the achievement of bond strength. Adhesive with 100% of the water replaced by a polymer latex was found to dry up too rapidly to allow sufficient time for the adhesive to interact with the substrate at the adhesive/substrate interface. The results reflect the importance of a proper mix design especially when works have to be carried out under hot and dry weather. The effects of moisture and movement due to shrinkage and creep are also discussed.
Keywords: Tile, Bond, Polymer, Movement joints, Workmanship
Assessing Building façades Using Infrared Thermography
Authors: M.Y.L. Chew
Source: Structural Survey : Volume 16, Number 2, 1998, pp. 81-86
Abstract:
The applicability of infrared thermography for assessing building façades was studied. Results from the laboratory experiments highlight the importance of the environmental conditions on the accuracy of technique. The thermograms were found effective in showing the simulated anomalies in test samples.
Keywords: Buildings, Environment, Joints
The Study of Adhesion Failure of Wall Tiles
Authors: M.Y.L. Chew
Source: Building & Environment:, Volume 27, Number 4, 1992, pp. 493-499.
Abstract:
This paper summarizes some of the important findings from a research project designed to study the various causes of why adhesion of wall tiles fails. The findings from this study indicated the importance of the environmental effects on the performance of tile adhesive. The selection of the appropriate tile adhesive for outdoor applications where the adhesive will be subjected to thermal and moisture movements needs careful consideration. It was found that the effect of temperature during application on the development of bond strength is significant. The storage temperature was also found to play an important role in the bond strength development although not as marked. The effect of thermal and moisture induced movements of the tile on adhesive strength was also found to be significant.
Among the four types of adhesives tested in this study, it was found that adhesive with approximately 50% of the water replaced by a polymer latex has the most consistent performance in the achievement of bond strength. Adhesive with 100% of the water replaced by a polymer latex was found to dry up too rapidly to allow sufficient time for the adhesive to interact with the substrate at the adhesive/substrate interface. The results reflect the importance of a proper mix design especially when work has to be carried out in hot and dry weather. This report resulted with some recommendations for the achievement of a good bond strength when using tile adhesive under severe environmental conditions.