Search

Commercial panelized rainscreen facade 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.

The toxic smoke production of four rainscreen façade systems were compared during large-scale fire performance testing on a reduced height BS 8414 test wall. Systems comprising 'non-combustible' aluminium composite material (ACM) with polyisocyanurate (PIR), phenolic foam (PF) and stone wool (SW) insulation, and polyethylene-filled ACM with PIR insulation were tested. Smoke toxicity was measured by sampling gases at two points - the exhaust duct of the main test room and an additional 'kitchen vent', which connects the rainscreen cavity to an occupied area. Although the toxicity of the smoke was similar for the three insulation products with non-combustible ACM, the toxicity of the smoke flowing from the burning cavity through the kitchen vent was greater by factors of 40 and 17 for PIR and PF insulation respectively, when compared to SW. Occupants sheltering in a room connected to the vent are predicted to collapse, and then inhale a lethal concentration of asphyxiant gases. This is the first report quantifying fire conditions within the cavity and assessing smoke toxicity within a rainscreen façade cavity. [Abstract copyright: Copyright © 2020 Elsevier B.V. All rights reserved.]

The Grenfell Tower fire has brought the regulatory system that permitted combustible materials on high-rise buildings in England into question. At the heart of that system is the BS 8414 test, and the BR 135 criteria used to demonstrate compliance with the Building Regulations. The test is empirical and the criteria arbitrary: there is no scientific link between test performance and how a building will perform in the event of a fire; nor any detailed analysis of why fires spread through façade systems which have passed the test. Following the Grenfell tragedy, the UK government commissioned a series of tests on Grenfell Tower-type facades, using BS 8414. This paper critically analyses BS 8414, the BR 135 criteria and the government tests. It shows that important aspects of the standard are poorly defined: the heat flux imposed on the façade is not measured and the fire load can vary by at least a factor of 2; the ambient ventilation has a significant impact on the thermal attack but is not adequately controlled; judicious location of the cavity barriers can confer compliance or failure on a façade system. As the vehicle for allowing combustible products on tall buildings, the test does not specify the extent of cavity barrier deployment, while ignoring features present in real buildings, such as windows, vents or other openings, despite a test rig height of more than 8 m. There is no restriction on debris, or molten or burning droplets falling from the façade during the test. The BR 135 criteria only specify that the test must run for the full 60 min duration without flames reaching the top, and the temperature rise at thermocouples 5 m above the fire chamber must only remain below 600°C for the first 15 min. It is unclear how the fire safety of the occupants behind the façade system can be ensured, when the criteria specify such a high temperature for such a short period, so early in the test. There is no direct connection between the façade system in the test and the actual façade system the results deem compliant. Worse, “desktop studies”, using large-scale test data, have been allowed to confer compliance on systems which have never been subject to the test. The UK government tests used heavy-duty welded aluminium “window pods”, preventing flames from entering the cavity within the façade. They also used a disproportionately large number of vertical and horizontal cavity barriers of a higher specification than required by statutory guidance. These aids to meeting the criteria are not proscribed by BS 8414-1 but are not commonly found in actual rainscreen system designs.

The adequate protection against meteorological conditions of rear-ventilated façades rests on the optimization of the construction design for the joints, cavity depths and wall interfaces. In the late 1990s and early 2000s several authors analysed the water management characteristics of open joints in rainscreen systems, although only few of them attempted to quantify infiltration rates into the air cavity. However, none of these studies provided reliable quantitative data on wind-driven rain intrusion to the water resistive barrier of rear-ventilated façades. The provision of this data will give the means of determining the moisture load to which the façade is to be subjected during a rain event and for which the façade must be able to manage. Consequently, the aim of his paper is to compare quantitatively the water management characteristics of different types of rear-ventilated façade systems by adopting a holistic approach to this kind of enclosure system. In order to conduct this study, three façade systems have been selected based on the type of fixing method and the design of the vertical and horizontal joints. Afterwards, the full-scale mock-ups have been built and tested in controlled laboratory conditions. During these tests, the amount of water infiltrating into the air cavity and the amount of water reaching the water resistive barrier have been measured. Finally, a comparison between the results obtained for every mock-up has been made.

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. Resumo O sistema de revestimento não-aderido (RNA) influencia o desempenho da fachada dos edifícios, pois impacta na durabilidade, estanqueidade à agua, estética e valorização do imóvel. O RNA, também denominado pelo mercado como fachada ventilada, é frequentemente utilizado em fachadas de edifícios residenciais, comerciais, novas construções, renovações ou retrofit, considerado também uma forma eficiente de reduzir os problemas de umidade da fachada. Entretanto, a ausência de normalização técnica específica limita o crescimento do uso desta tecnologia no Brasil. Além disso, no Brasil, existe a NBR 15575, partes 1-6 (2013), que estabelece critérios de desempenho, bem como os respectivos métodos de avaliação para avaliar os principais sistemas do edifício: estrutura, piso, vedações verticais, cobertura e instalações. Entretanto, esta norma pode somente ser parcialmente adotada para o RNA, pois a NBR apresenta critérios considerando toda a fachada e, não somente, o revestimento. No presente artigo são propostos critérios de desempenho e métodos de ensaio aplicados para RNA, particularmente abordando os requisitos de segurança estrutural (resistência a cargas de vento, e a impactos de corpo mole e corpo duro) e drenabilidade. Para este estudo, as seguintes atividades foram realizadas: revisão bibliográfica, estudo de caso e ensaios em protótipo para validar a proposta de critérios e métodos de ensaios.

In recent years, external wall fires (or facade fires) are occurring due to mixed contribution of exterior cladding and continuous insulation in the chimney like construction of rainscreen facades. In the present work, a new experimental setup is developed and demonstrated for the initial screening of facade assembly at a lab-scale. It incorporates the real physics for investigating the fire hazards of flammable polymeric materials and the chimney effect together. Different combinations of exterior cladding (Al-45, Al-45 Class 0, Al-45 Class B) and continuous insulation (Expanded polystyrene, Polyisocyanurate and Mineral wool) with and without chimney are selected for studying their fire behaviour. The pressure differential combining with re-radiation inside the cavity led 3–6 times higher mass burning rate, flame height and temperature in tests with chimney effect to that of without for the same combination of products. With chimney, secondary fire sources are generated due to the dripping of products which further enhanced the burning and spread rate. A critical width of the chimney (13–50 mm) is established at which maximum vertical fire spread was noticed. Furthermore, the visual observations indicated that the products having thin outer Al sheets are prone to 30% early structural failure. Comparison of results with large-scale tests validated the usefulness of the current setup as an intermediate test between small and large scale for studying fire behaviour of facade materials.

In recent years, lightweight steel-framed (LSF) constructions are considered sustainable and widely used worldwide. However, the LSF wall assemblies have the risk of durability failure in hot-humid climates. This study conducted fundamental research on the hygrothermal performance of LSF wall assemblies by characterizing the hygrothermal responses, modelling and validating the simulation models under hot-humid climatic conditions . Through measuring the relative humidity and temperature of various positions inside, four typical and full-scale LSF wall assemblies were tested thoroughly and comparatively on two room-like test cubes in Guangzhou, a hot-humid city in China. It was found that the ventilated rainscreen provided better hygrothermal responses of the wall assemblies than the face-sealed cladding; the closed-cell external insulation could significantly improve the hygrothermal responses of the wall assemblies with stucco cladding; generally, wall assemblies with ventilated rainscreen and external insulation exhibited the best hygrothermal response in a hot-humid climate, followed by wall assemblies with ventilated rainscreen, wall assemblies with face-sealed cladding and external insulation and wall assemblies with face-sealed cladding. Furthermore, the measured data were used to model and validate the simulation models of the four typical wall assemblies in software. It was shown that hygrothermal simulation is sufficient for evaluating the long-term hygrothermal performance of LSF wall assemblies in hot-humid climates, and relatively conservative settings are necessary for evaluating cases with great uncertainties. Overall, this study could lay a foundation for better assessing and improving the hygrothermal performance, durability and sustainability of LSF buildings in hot-humid climate regions worldwide.

The facade is one of the most complex parts of a building, performing multiple objectives of value to the occupants. The frequency of facade fires in tall buildings is increasing, therefore it is crucial to understand the behaviour of such facades in a fire, but there is currently no theory, model, or series of experiments that allows this understanding. This paper takes a top-down, data driven approach to understanding facade behaviour by analysing a unique database, named KRESNIK, containing 252 commercial facade fire tests, the first time such data has been analysed. We found that the outputs from these tests were correlated, which could be used to gain more information of facade performance than simply pass or fail; and that the different layers of a facade can have a significant effect, particularly the addition of a cavity. Rainscreen facades performed the worst (45% failed), whereas none of the ETICS or sandwich panels in KRESNIK failed. We also found that the choice of cladding material of these rainscreens is the most important factor in driving their fire performance, but that neither its total fuel nor its conductive resistance can predict fire performance. Finally, we found that repeated tests of identical facades could have major variations in the outputs, but that whether the facade ignited or not tended to remain consistent across repeats. These results help to identify critical factors in facade flammability, better informing engineering decisions, and contributing to the design of safe tall buildings.

The impact of the ventilation cavity design on the energy performance of the rainscreen wall assembly was numerically investigated in CFD. The ventilated cavity design parameters considered were the cladding material type (i.e. Fibre cement, brick, and metal cladding), the sheathing membrane emissivity coefficient (i.e. 0.1–0.9), the ventilated cavity height (i.e. 1H and 2H) and the air gap width (i.e. 13 mm–50 mm). The CFD model was validated with experimental data and a dynamic simulation for a typical hot day and cold day is performed for a timestep interval of 5 min. The heat flux through the wall assembly was compared amongst the design alternatives. For the range of parameters considered, the ventilated cavity construct with brick cladding, sheathing membrane emissivity of 0.1, one-storey ventilated cavity, and 13 mm air gap width minimized the heat loss for a typical cold day. However, ventilated cavity construct with brick cladding, sheathing membrane emissivity of 0.1, one-storey ventilated cavity, and 50 mm air gap width minimized the heat gain for a typical hot day.

Four reduced-height (5 m) BS 8414-1 facade flammability tests were conducted, three having mineral-filled aluminium composite material (ACM-A2) with polyisocyanurate (PIR) and phenolic (PF) foam and stone wool (SW) insulation, the fourth having polyethylene-filled ACM (ACM-PE) with PIR insulation. Each facade was constructed from a commercial facade engineer’s design, and built by practising facade installers. The ACM-PE/PIR facade burnt so ferociously it was extinguished after 13.5 min, for safety. The three ACM-A2 cladding panels lost their structural integrity, and melted away from the test wall, whereupon around 40% of both the combustible PIR and PF insulation burnt and contributed to the fire spread. This demonstrates why all facade products must be non-combustible, not just the outer panels. For the three ACM-A2 tests, while the temperature in front of the cavity was independent of the insulation, the temperatures within it varied greatly, depending on the insulation. The system using PF/A2 allowed fire to break through to the cavity first, as seen by a sharp increase in temperature after 17 min. For PIR/A2, the temperature increased sharply at 22 minutes, as the panel started to fall away from the wall. For SW/A2, no rapid temperature rise was observed.

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.

© 2015 Elsevier Ltd. The article at hand presents the results of an extensive field study in which the air change rate behind rainscreen claddings has been measured. In total eight different full-scale test walls have been tested. The main parameter variations are: 1) the cladding system (brick veneer and sidings), 2) orientation (South-West and North-East) and 3) area of ventilation openings. To increase the reliablity of the results four measuring techniques to determine the air change rate have been applied. The accuray and applicability of these methods have been discussed in a previous paper. The current article focusses on the impact of the three abovementioned parameter variations on the overall air change rate. Moreover their effect on the hygrothermal conditions in the cavities will be outlined.The results show that the cavity ventilation for brick veneer (1-10 ACH) is two order of magnitude lower than behind sidings (100-1000 ACH). This difference also reflects on the drying potential of both systems. The vapour content behind the sidings follows closely the outer climate. In contrast the vapour pressure behind brick veneer can be significantly higher than the outer climate which is induced by its moisture buffer capacity and its low ventilation rate. publisher: Elsevier articletitle: Field study on the air change rate behind residential rainscreen cladding systems: A parameter analysis journaltitle: Building and Environment articlelink: http://dx.doi.org/10.1016/j.buildenv.2015.09.012 content_type: article copyright: Copyright © 2015 Elsevier Ltd. All rights reserved. ispartof: Building and Environment vol:95 issue:1 pages:1-12 status: published

In recent years, an innovative system for a rainscreen facade system with low thickness and large tiles of porcelain stoneware has been patented. This paper presents the results of a large experimental campaign investigating mechanical performance of a ceramic tile in 3different configurations: tile without net, with fiberglass net glued on the back, and the entire cladding system (slab/net/frame). The main objective is to determine material mechanical characteristics (e.g. modulus of rupture and Young's modulus) considering a protocol of artificial ageing (fatigue test, freeze-thaw, heat-rain, H2O Saturation, heat treatment, accelerated corrosion SO2 and NaCl, irradiation UVB and condensation) in order to understand the possible decay during the service life and consequently to design the technological solution of a rainscreen facade system. The results showed that on the modulus of rupture the most influences ageing effects are fatigue test and freeze-thaw while the influence on young's modulus is negligible. Furthermore, it is necessary to consider second-order effects for the evaluation of the resistance and, finally, that the fiberglass net does not lead to a significant increase in resistance.

© 2015 Elsevier Ltd. 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. publisher: Elsevier articletitle: Experimental analysis of cavity ventilation behind rainscreen cladding systems: A comparison of four measuring techniques journaltitle: Building and Environment articlelink: http://dx.doi.org/10.1016/j.buildenv.2015.01.030 content_type: article copyright: Copyright © 2015 Elsevier Ltd. All rights reserved. ispartof: Building and Environment vol:87 issue:5 pages:177-192 status: published

Residential buildings are now better engineered to manage rainwater following the leaking building problem in New Zealand. The next challenge is to improve the weathertightness of medium-rise buildings which often use joint details widely applied on low-rise buildings but are subject to higher wind pressures and surface runoff rates. This study begins to address this challenge by measuring the water leakage performance limits of the following common flashings with static and dynamic rain and wind loads to see how their performance might be improved: (a) Horizontal H and Z jointers between direct fixed sheet claddings, (b) The window head flashing in a cavity wall, (c) A horizontal apron flashing at the junction between a roof and wall. At this stage, water penetration resistances have been measured but the data has not yet been discussed in the context of wind pressures and rain loads on mid-rise buildings. All of the joints were found to resist water leakage to pressures equivalent to the hydrostatic head of the upstand, so long as there were no air leakage paths through the joint. When vents were added, or openings were present that might arise due to construction tolerances, then the onset pressure for leakage was found to fall by as much as 50%. Vents, of course, are essential for ventilation drying in rainscreen walls and even with vents present, the onset of leakage was at generally at least twice the 50 Pa wet wall test pressure applied in New Zealand. Opportunities were found to improve the way vented joints deal with runoff by enlarging the gap between the cladding and flashing. This prevented the outer joint volume from filling with water and occluding the vents. The apron flashing was found to cope better than a window head joint with runoff, because of the larger 35 mm vertical gap between the cladding and apron.

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.

The major problem in ventilation systems designing is an empiric range of parameters of an air cavity and rustics between cladding panels which results in unventilated layers emergence. Whereas insufficient air interchange causes icing of as substructure elements which come out into a ventilated air cavity as facing outer layer in winter period, and reducing of heat-protective properties of the structure in whole. The aim of this survey is to elaborate the methods meant for calculating the parameters of hydraulic airflow in a ventilated air cavity which allow determining rational and optimal dimensions of hydraulically optimal air cavity in rainscreens of buildings and other constructions. As an outcome it has been specified that it is necessary to design a ventilated rainscreen cladding with a ventilated air cavity expanding from bottom to top with the purpose to reduce the losses.

Hygrothermal simulation programs are commonly used by design engineers to analyse moisture performance of building envelopes. For ventilated assemblies, programs typically require the user to enter cavity ventilation rates. If such input data are not prepared on physical grounds, it can impair the quality of the simulation results. In earlier papers: (1) estimations of ventilation rates in experimental walls based on cavity air velocity measurements; (2) comparative calculations based on monthly and annual tabular climate data, a simple driving force model and models of cavity airflow and heat balance, have been presented. In this study, the models and hourly climate field data were used to perform calculations of transient cavity ventilation rates for comparison with previous experimental results. For 13 different time periods extending from 24 to 91 h, the calculated average ventilation rates were within or very close to the experimentally estimated limits for the ventilation rate. Additionally, the calculations captured the temporal variability and the physical cause of ventilation airflow in the cavities reasonably well. The applied calculation methodology can be developed into a user friendly approach to estimate realistic ventilation rate input data for hygrothermal purposes. Limitations and possible improvements of the methodology are discussed. The influence of the accuracy and resolution of the ventilation rate input data in simulations is demonstrated in a case study.

In residential buildings, a typical rainscreen exterior wall system often incorporates an exterior membrane mechanically fastened to an exterior sheathing. This thin and flexible membrane is an important component of the wall system and performs multiple functions. Under a negative air pressure differential, that is, wind suction, the exterior membrane can deform or balloon. The membrane ballooning has important implications on many performance issues in the rainscreen exterior wall system. That the membrane ballooning changes the air cavity volume and therefore affects rainscreen pressure equalization is one important implication. Since the 1980s, many theoretical pressure equalization models have been proposed. This article takes a unique viewpoint and focuses on reviewing how the theoretical screen pressure equalization models consider the effect of membrane ballooning. It is believed that such a review is essential for future study on how to incorporate the membrane ballooning into the pressure equalization model.

This paper analyses undercut anchorage technology, in particular its behaviour and performance as a fixing system for dimension stone cladding of rainscreen façades. Based on a number of mechanical tests using various types of Portuguese stone – three igneous, two sedimentary and one metamorphic – a study was carried out to investigate the relationship between the flexural strength and breaking load of specific and very common stone types. Several physical and mechanical characterisation tests and 130 pull-out tests with 6 and 8 mm cone bolt threads were performed to determine the pull-out load failure on six different stone types: three granite, two limestone and one marble. Finite-element stress analyses were carried out, and the test results were the basis for calibrating a simple formula that can be used to estimate the stone's breaking load at the undercut anchorage. Stress concentration factors are proposed to take into account the undercut drill hole geometry and the specific properties of each type of stone. Stone specimens from the same batches were subject to pull-out force tests using dowel anchorages, whose values were then compared with the breaking load of undercut anchorages. Results are discussed and conclusions are drawn based on tensile stress values by comparing the test results, the finite-element method and the proposed semi-empirical formulations for the same breaking load.

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 facade 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.

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.

In this paper the thermal behaviour of a rainscreen ventilated facade has been investigated both experimentally and numerically. Field measurements were performed during the 2009/10 winter season in a test building located in San Mauro Pascoli (Italy) having a squared base of internal dimension of 2.89 m and a total internal height of 7.75 m. The external walls of this tower are rainscreen ventilated facades with a 24 cm air cavity and an external side composed of stoneware with open joints. Ventilation grills are located at the top and at the bottom of the tower. In this work the modelling of the test building using a dynamic thermal simulation program (ESP-r) is presented and the main results discussed. In order to study the rainscreen ventilated facade three different multi-zone models were defined and the comparison with the experimental results has been used in order to select the best ESP-r air flow network for the modelling of this kind of envelope component. The thermal analysis of this envelope component evidenced that the ventilated facade is able to reverse the direction of the heat flux through the envelope in regions characterized by large solar irradiation during the winter and moderate wind velocity, when the indoor-outdoor air temperature difference is small, thereby reducing the energy consumption required for indoor heating.

PurposeThe purpose of this paper is to design and develop a model for testing watertightness of rainscreen walls.Design/methodology/approachA test model was developed to determine the time to achieve equalisation and tightness rate of the rainscreen under investigation. Other tests include the distribution of wind loads to each rain screen layer, with the amount of water infiltrating into the cavity and the tightness rates.FindingsIt is found that the cavity must be compartmentalized, separating zones with different pressures. Vertically, corners and lateral stripes, 2 or 3m wide, must necessarily be compartmentalized. Horizontally, it is very convenient to compartmentalize the cavities of each floor, or at least every two floors (maximum 6m). When a cavity is not compartmentalized and tight, there will be air currents moving inside the cavity, and therefore the amount of infiltrated water through vents and joints will increase.Originality/valueThe paper demonstrates its value by developing a model to investigate the watertightness of rainscreen walls.

The use of open-vented rainscreen has a long history beginning with tile-hung walls. More recently larger panels have been employed as the use of rainscreen walling has developed. This expansion has been due to the need to refurbish existing buildings by overcladding them and also due to the advantages of systemised building for new build, not least the rate at which enclosure may be achieved. In new-build construction the rainscreen panels may be used in conjunction with a back wall of masonry or framed construction. Integral walls incorporating a curtain wall system with decorative rainscreen panels are also used.

This paper presents the results of the wind tunnel experiments and compares them with full-scale data obtained at the Technical University of Eindhoven (TUE) building in Eindhoven, The Netherlands. Difficulties with the wind tunnel testing are discussed. The objective of the study is to quantify the parameters involved in the design of pressure-equalized rainscreen (PER) walls in order to establish specific design guidelines for standards and codes of practice. Comparisons with the currently available limited provisions show clearly their inadequacy.