Rainscreen Cladding Research Articles

Hygrothermal resilience of typical lightweight steel-framed wall assemblies in hot-humid areas under future climate uncertainty

Ensuring the hygrothermal performance of lightweight steel-framed (LSF) wall assemblies is critical for the sustainability of LSF buildings in hot-humid regions; however, climate change poses new challenges. Therefore, this study aimed to bridge the gap in understanding the characteristics of hygrothermal load changes and the hygrothermal resilience of different LSF wall assemblies. Future climate data for each decade of this century (from 2030 to 2090), under various carbon emission scenarios, were generated based on a typical meteorological year (TMY) for hot-humid areas to evaluate the impact of climate change on hygrothermal loads. The hygrothermal resilience of four typical LSF wall assemblies, with either ventilated rainscreen cladding or face-sealed stucco cladding, with or without external insulation, was evaluated through simulation and comparative analysis. The results indicated that the thermal load would increase with increasing carbon emissions and over time, with the annual average external temperature peaking at 25.8 °C by the end of this century. The frequency of months with a high or critical moisture load would increase, although the moisture load may fluctuate across scenarios and years. Consequently, the cooling and dehumidification loads may increase by 52–60 % and 40–88 %, respectively. The hygrothermal risk within the walls may increase, with maximum increases of 2.8–8.0 % in the annual average relative humidity, 2.7–3.0 °C in the annual average temperature, and 10–35 % in the wetness duration. However, the impacts could be reduced by using ventilated rainscreens and external insulation, with further precautions needed to mitigate the increasing hygrothermal risk in areas with thermal bridges and rainwater leakage, as well as at the outer interface of the external insulation. These findings could provide a reference for the design of LSF buildings adapted to climate change in hot-humid areas.

Ultra-High-Performance Concrete (UHPC) - Applications Worldwide: A State-of-the-Art Review

Research is in progress on the applications of ultra-high performance concrete (UHPC) as a new additive material in construction technology. Over the last twenty years’ significant improvements have been achieved in mechanical properties of UHPC, such as its strength, workability, and ductility, with further improvements made in self-placing properties, higher density, and durability compared with normal concrete. One of the biggest advantages offered by ultra-high performance concrete over normal concrete is the possibility to minimize the cross-sectional dimensions of the structural elements. UHPC can be used to provide significant long-span members, whilst also showing less variation, creep, and drying shrinkage compared to conventional concrete. After many years of development and research into UHPC’s properties, it is being used in commercial applications to meet the rising demand for quality constructions. Many projects in the world started using UHPC for different construction objectives such as long spans, columns, jacketing, rain-screen cladding systems, panel systems, façades, etc. Furthermore, there are not enough sources in the literature describing mixture design, preparation, and curing. This research gives an overview of the uses of UHPC in structural and architectural applications.

Lustrous wrappings: Complex color and collaborative practices in the contemporary ceramic facade

AbstractGlazed ceramic cladding is a material with a very long history of use in the built environment, whether as roof tiles, wall tiles, or more recently, as part of a rainscreen cladding system. A key factor in the resurgence of interest in ceramic as a cladding material—in addition to its inherent qualities of sustainability, malleability, durability, and fire resistance—is as a means of incorporating color into the facade. Although polychromatic facades are commonly achieved using tessellation of a range of single‐colored elements, this article will focus on complex layered and variegated color and texture within a single component. Historical glazes, such as the blue‐red of Chinese Jun ware pottery from the 12th century CE were produced through carefully controlled reduction kiln processes, yet retained an element of uncertainty in the resultant patterns and remain an inspiration for contemporary ceramic artists. Drawing on historical research, literature review and interviews with ceramic artists and industrial manufacturers, six case studies from the United Kingdom and China are discussed that show collaborative processes at different scales of operation. These combine unique artisan and artistic glazes, with standardized, rigorously tested, and internationally manufactured products. These “fusion glazes” refer to historic hand‐made practices to bring an element of unpredictability, and a layer of complexity in terms of color, texture and luster.

FINITE ELEMENT STUDY OF COMBINED THERMAL-WIND LOADING EFFECTS ON RAINSCREEN

Sotech is a leading manufacturer of bespoke rainscreen cladding and architectural façade systems, where aluminium cladding façade is of particular interest. Necessarily, the design of façade system is required to meet safety and stability requirements, which is conventionally the deformation due to wind load. However, it is questionable that the thermal load is normally neglected, particularly during an extremely hot weather. For the benefit of Sotech in terms of design reliability, it is important to factor in thermal load to acquire for comprehensive deformation results. Consequently, the aim of this study is to investigate how the aluminium cladding façade reacts to a combined loading, which is the combination of wind load and thermal load, using finite element analysis. In the model, the gravitational load will be considered, and the combination of wind loads up to 50 mph and thermal loads from -30°C to 35°C are applied to the aluminium cladding panel. Typically, the material is defined as aluminium alloy, which is easy to manufacture and has a high strength to weight ratio. The key finding is that addition of thermal load to wind load is not necessarily topping up the deformation, since there can be an effect of wind load being negated by thermal load. This study lays a foundation for Sotech to improve the design standard.

Ventilated rainscreen cladding system subframe contribution to annual source energy use in mid-size office buildings

Commercial panelized rainscreen façade systems have gained in popularity in the United States and Europe over the last 10 years. These systems are characterized by external subframe support structures which exist within the ventilated cavity of the assembly and utilized various bracketed or girted frames with multiple point support fastenings through the building envelope. Given the popularity of these systems and the increasing mandates for higher performing envelopes – subframe applications and products which increase thermal resistance and decrease thermal bridging are becoming more prevalent. This research will compare four common subframe assemblies based on annual source energy output for a mid-size office building. The assemblies will be simulated in all eight ASHRAE climate zones to provide comparative analysis per assembly and exterior environment.Accurate assessment of a wall assemblies thermal performance requires its cumulative Y-value contribution based on the total envelope area, detailed transitions, and material construction. The inclusion of specific value inputs for non-repeating linear and repeating point thermal bridging conditions provide a more accurate perspective into building energy efficiency and its relationship to envelope performance for all wall types analyzed. This method of thermal simulation and evaluation is necessary for accurate envelope and building performance analysis.

Impact of Grenfell Tower fire disaster on polyisocyanurate industry

The paper summarizes commonly available information on the fire of the Grenfell Tower, which took place in Central London on 14 June 2017. The fire was very similar in its nature to several other spectacular fires at tall buildings, which have happened around the world since 1999 but unlike the previous one, the London fire claimed an enormous number of victims – 71. The tragic outcome of the fire was blamed on a combination of several human and natural factors: faulty evacuation procedures, unsuitable fire extinguishing equipment, mistakes by the housing association managing the building, lacking fire safety provisions in the tower, weather, confusing building regulations, etc. However it was established that the main reason for so tragic an outcome of this fire was the speed of fire spread via decorative aluminum composite materials (ACM) containing polyethylene (PE), installed on the outer of a building as a part of a rain-screen cladding system. The other part of the system was polyisocyanurate (PIR) thermal insulation. The paper focuses on the role of PIR in this fire and a couple of practices in the PIR industry highlighted by the tragedy. It reflects on the origin of PIR and evolution of PIR technologies as well as PIR definition. Finally it reports on a bottom-up initiative started at the Polyurethanes 2017 Conference aiming at changing current attitude of the European thermal insulation industry to Open Access to reports on fire testing of thermal insulation products. This small but concerted effort of scientific and industrial thermal insulation communities has a good chance of helping to drive further improvement of fire resistance of thermal insulation and to restore public confidence in these important materials.

Ventilated cladding systems: structural and drainability performance criteria

Abstract Cladding systems have significant effect on the performance and durability of building façades, contributing to the building watertightness, property valuation, aesthetic finishing, and decoration. Non-adherent cladding, also named rainscreen cladding or ventilated cladding, is currently used in residential and commercial buildings, new constructions, or retrofit operations, and it is considered an efficient measure to improve the moisture safety of building envelopes. Therefore, the absence of Brazilian normalization to ventilated cladding systems is one of the difficulties limiting its increased local application. In Brazil, a technical standard, NBR 15575, parts 1-6, (2013), establish the general performance requirements and test methods to evaluate residential building systems including structure, wall, floor, coverage, and hydraulic installation. However, this standard cannot be integrally applied to the cladding systems because it was developed considering the vertical wall system as a whole. In this study, we propose the criteria and test methods for assessing ventilated cladding systems while taking into account the structural safety (wind loads resistance, hard and soft impact resistance) and drainability requirements. The following activities are performed: literature review, practical case study, and tests on prototypes for validation of the proposal. The tests allow verification of the feasibility of the criteria and tests methods proposed. In addition, the proposal makes it possible to guide design, construction, and maintenance needs, thereby inducing the growth of this technology in Brazil.

To the Problem of Bearing Capacity and Operational Reliability of Suspended Ventilated Facade

Suspended ventilated facades are the most common types of finishing and heat insulation of existing buildings and construction projects. Today, a wide variety of rainscreen cladding systems exist, offering different bearing structures, cladding subframes and cladding materials. There is a great variety of cladding materials employed for suspended ventilated facades, the most popular being ceramic granite and composite panels.The article describes a new design solutions for suspended ventilated facades, developed in National Research Moscow State University of Civil Engineering.

Innovative Uses of Rain Screen Cladding. CFD and Gas Dispersion Analysis of a Prototype

In this work, both CFD and CH4 dispersion analysis in rain screen cladding were carried out, in order to reduce the visual impact of Natural Gas distribution network in civil buildings ensuring high safety standards. In the first part of the work it was conducted the parametric analysis in order to identify the main physical parameters that influence the air velocity in air-gap. Subsequently, CFD simulations were carried out in order to evaluate how the geometric and constructive characteristics can influence the air velocity inside the cavity. In particular, were realized both 2D and 3D models, and was used Ansys Fluent 6.3 software. Finally, Natural Gas dispersion analysis was carried out, in order to evaluate the safety against explosive atmosphere.

Multiple-inlet BIPV/T Modeling: Wind Effects and Fan Induced Suction

Building Integrated Photovoltaic/Thermal (BIPV/T) collectors take up the role of energy and heat production, while acting as a rain-screen cladding. A multiple inlet BIPV/T system counters the effect of high temperature stratification on the PV layer, by enhancing the convection inside the air channel with the introduction of more than one openings for the intake of fresh air that break up the surface boundary layer. To investigate the uniformity of heat extraction from the PV panels, the fluid mechanics of the system are studied separately from the thermal effects. A numerical flow distribution model, which incorporates wind effects, is introduced for the optimal design of multiple inlet systems so as to have flow rates through each inlet that maximize the heat extracted from the PV panels.

Experimental analysis of cavity ventilation behind rainscreen cladding systems: A comparison of four measuring techniques

The present article elaborates on the comparison of four measuring techniques quantifying the ventilation rate behind typical cladding systems in wall elements. In total eight full-scale test walls have been investigated in a test building located in a maritime temperate climate (Belgium). Two different commonly used cladding systems are studied: (a) brick veneer and (b) fibre cement sidings. The test walls were installed on the Southwest and Northeast façades of the building corresponding to the orientations with most extreme exposure regarding solar radiation, wind directions and wind-driven rain. In total four different measurement techniques to quantify the ventilation rate in these systems have been applied: a) tracer gas techniques, b) indirect method based on pressure measurements, c) direct method based on anemometers and d) method based temperature and relative humidity registration. The results indicate that the ventilation rate behind vented brick veneer is two orders of magnitude lower than behind ventilated cladding systems with sidings. It was found that the most appropriate measuring technique of a wall system is depending on the ventilation rate, and hence on the type of cladding. For brick veneer claddings, the method deriving the air flow rate from the pressure gauges was found to be most suitable. In the wall systems with sidings, on the other hand, the ventilation rates were sufficiently high to be measured accurately with the anemometers.

Design of a Suspended Ventilated Facade with Composite Facing

A suspended ventilated façade is the most efficient solution to insulate and improve aesthetics of both a refurbished and a newly built building. Today, a wide variety of rainscreen cladding systems exist, offering different bearing structures, cladding subframes and cladding materials. Composite cladding is the most widely used.

Ventilated rainscreen cladding: A study of the ventilation drying process

The air exchange in rainscreen walls is expected to provide ventilation drying if excess moisture is absorbed in the wall construction. In an earlier paper, we presented a cavity airflow model and measurement based estimations of air change rates (ACH) in south-facing experimental walls. Here, focus is on the ventilation drying process and its practical implications. ACH in the experimental walls were calculated and converted into drying rates at different stages in the drying process. Furthermore, changes in the drying rates due to changes in the cavity design and in the outdoor climate were investigated. The significance of the drying rates was demonstrated in a case study.Findings showed that the cavity design is of major importance for the drying rate if the material adjacent to the cavity is wet over its entire extension. For such extreme cases, a light façade colour, vented horizontal battens and, in particular, a small cavity depth, are adverse factors for the drying rate. As the drying process proceeds and the moisture transport from the material to the cavity air becomes dependent on vapour diffusion, the drying rates for different cavity designs tend to be evened out. If the resistance to vapour flow in the material reaches high levels, a favourable outdoor climate is significantly more important than the cavity design to promote drying. Also for the case where the material adjacent to the cavity initially is only locally wet, findings showed that the cavity design is of minor importance for the drying time.

Ventilated rainscreen cladding: Measurements of cavity air velocities, estimation of air change rates and evaluation of driving forces

To analyse the moisture performance of wall systems with a ventilated rainscreen cladding, the air change rate per hour (ACH) is required. However, the average ACH and its variation depend on many factors. This study focuses on performing field measurements of air velocities and temperatures in south oriented wall cavities characterised by either vertical wooden battens or horizontal vented metal battens. A physical cavity airflow model together with laboratory test of loss factors were used to analyse the data and interpret the results.With vertical battens, findings estimated the average ACH during a measurement period to be 230–310 ACH. In the cavities with horizontal battens, the ACH was 60–70% lower. The daily variations were considerable and hours with solar radiation and clear skies resulted in ACH that exceeded the average values 2–3 times. In contrast to airflow induced by thermal buoyancy, wind-induced airflow was irregular with frequent changes in both velocity and direction. This pattern was observed independent of the angle between the wind and the cladding. The frequent changes in flow direction significantly reduced the efficiency of wind-driven airflow to create air exchange. The wind-induced airflow in wall cavities with a pronounced non-linear relationship between the driving force and the air velocity is suppressed in the presence of buoyancy. For rainscreen claddings exposed to many hours of solar radiation, this effect increases the possibility of accurate estimations of ACH.

Capturing a Scheme Design for Rainscreen Cladding

Abstract: This article reports on the exploratory application of product modeling techniques to the cladding of buildings. More specifically, it focuses on the development of a product model to formally capture the scheme design for a building that is clad with “rainscreen cladding.” Such a model would enable the cladding scheme design to be conveyed in digital form throughout the subsequent procurement process. Rainscreen cladding was selected as being an exemplar of the cladding types used on buildings, although the resulting product model provides for the capture of visual and functional requirements. The article introduces the wider context of the research, explains the particular focus adopted for the modeling, describes the as‐developed product model and includes an outline of prototype software that was developed specifically to help validate the model. The resulting product model could readily be reworked as a cladding extension to the IFC or the CIS/2.

Tradition and innovation: timber as rainscreen cladding

This paper describes the use of timber as a rainscreen cladding on David Chipperfield's River and Rowing Museum at Henley. The extensive use of green oak in this way is the key to a precise and beautifully crafted building and was the result of collaboration between the architects and the Timber Research and Development Association. This use of timber represents a major shift in the work of David Chipperfield from concrete toward a wider palette of materials. Henley is also an important example of a recent trend in the development of timber as an external cladding material. Timber cladding as a rainscreen will be discussed in the context of the Henley project in terms of its performance factors and the design and construction process, and analysed with a view to drawing some conclusions for its future use.