Wind-driven Rain Research Articles

Erosion anisotropy analysis of construction materials as a key tool for strengthening preventive conservation strategies in built heritage

In this paper, we present an innovative Erosion Anisotropy Analysis as a pioneering tool to discern the most harmful hydrometerological agents and their predominant directions of impact on built heritage. The proposed Erosion Anisotropy Analysis includes: 1) the analysis of weathering, bio-weathering and erosion processes affecting the building materials; 2) analysis of climatic series identifying preferential directionality of hydrometeorological agents; 3) erosion quantification using photogrammetric models; and 4) comparative analysis between both erosion and climatic anisotropy models.The proposed analysis is applied to the Cerrillos Tower (Almería, Spain), which is considered a paradigmatic case study due to their location and exposure conditions. Results determinate the primary vulnerability directions against hydrometeorological agents (N200–330°E) and highlight solar radiation, wind and wind-driven rain as the most damaging factors. Moreover, the Erosion Anisotropy Analysis describes the erosion patterns developed as well as their anisotropic distribution in the Tower.The proposed methodology is a benchmark for designing and dimensioning effective preventive measures to mitigate their impact under current climatic conditions as well as to prevent future scenarios within the global framework of climate change.

Impact of upstream buildings on Wind-Driven Rain Loading: Refining Obstruction Factor in ISO semi-empirical model based on CFD

CFD is a valuable tool for assessing Wind-Driven Rain (WDR) loading, one of the most important environmental loads for façade design. The majority of previous studies on this topic have primarily concentrated on simple building configurations, i.e., stand-alone buildings. Hence, prior findings may not be applicable to consider the impact of upstream buildings in urban areas, which significantly alter wind flow field, consequently, change WDR loadings on downstream building facades compared to the stand-alone building. Part A: four different steady-state RANS models (i.e., standard k−ω, realizable k−ε, RNG k−ε, and standard k−ε) coupled with the Eulerian Multiphase (EM) technique (RANS-EM) are compared and implemented using OpenFOAM-7. These models are validated and verified based on wind-tunnel and field measurement data obtained from the literature for a six-story mid-rise residential building located in an urban area in Vancouver, Canada. The study considers 13 distinct rainfall events, for the test building with/without overhangs. All four RANS models are deemed suitable for modeling WDR in urban areas, while the steady-state standard k-ω RANS-EM approach without incorporating turbulent dispersion showing slightly better performance, thus utilized for the reminder of the study. Part B: a sensitivity analysis is presented on how the upstream buildings influence the WDR loading on a downstream building, denoted as Obstruction Factor. A comparison between the CFD and ISO semi-empirical model shows significant discrepancies, potentially reaching up to factors of 5. Thus, updated Obstruction Factors are suggested to enhance the ISO model for more accurate estimation of WDR loads.

Hygrothermal assessment of three bio-based insulation systems for internal retrofitting solid masonry walls

The present project investigated the hygrothermal performance and risk of mould growth in solid masonry walls retrofitted internally with three diffusion-open bio-based insulation materials (two loose-fill cellulose and one hemp fibre), installed in test containers with controlled indoor climate. Focus was on bio-based insulation materials, as these are upcoming due to necessary CO2 reductions and because the hygroscopic properties of bio-based materials are different from traditional insulation materials like mineral wool therefore, some manufacturers claim a vapour barrier is unnecessary, even in relatively cold climates. The project was a large experimental study in two reefer containers with reconfigured facades, in which solid masonry walls with embedded wooden elements were constructed. The study focused on the conditions in the masonry/insulation interface and in the embedded wooden elements. The effect of hydrophobization and different indoor moisture loads were also investigated. Moreover, the bio-based insulation systems were compared with a wall insulated with the traditional mineral wool and vapour barrier system. Relative humidity and temperature were measured at several locations in the test walls for 1 year and 9 months. Measurements show that exposed masonry walls retrofitted internally with diffusion-open bio-based insulation materials resulted in unacceptably high moisture levels (>80% RH over longer periods). Lower moisture levels were observed when the internal insulation was combined with hydrophobization against wind-driven rain, but unacceptably high moisture levels still occurred (60%–70% in summer and 95%–100% in winter in the interface). Hydrophobization reduced the moisture levels in the interface and embedded wooden elements only in walls facing southwest, which is the direction with the most wind-driven rain. Mould growth tests showed no growth in the interface in walls insulated with cellulose insulation (mycometer surface value <25). Meanwhile growth was found in all four walls insulated with hemp fibre matts (mycometer surface value >400).

Analysis of numerical simulations and semi-empirical models on distribution characteristics of wind-driven rain on low-rise building facades

Wind-driven rain (WDR) is a significant contributor to indoor moisture in buildings, directly impacting the thermal and moisture performance of facades. Previous research on WDR in China focused on a limited number of low-rise pilot buildings, whose materials, shapes, and environmental settings are not entirely representative of typical applications. Aim to improve the accuracy of WDR predictions on low-rise building facades, there is a need for assessing different WDR calculation methods under various rain events. The paper presented high-resolution WDR measurements from a low-rise concrete building in Chongqing to investigate the distribution of WDR on building facades under local meteorological conditions. The study compared the performance of numerical simulations and two semi-empirical models with different meteorological data averaging techniques. The results indicated that Computational Fluid Dynamics (CFD) simulations using the Eulerian multiphase (EM) model more closely matched the actual catch ratio across various locations and the WDR amount across the facade, with errors ranging between 10%-25 % and 2%–23 %, respectively. Furthermore, the ISO model with weighted averaging (WA) technique outperformed others in estimating catch ratios at various locations and the WDR amount across the facade, particularly when estimating the midline catch ratio. When considering both cumuliform and stratiform rainfall, the arithmetic averaging (AA) technique was a viable method for the ASHRAE model to forecast WDR. The ISO model's predictions corresponded to 54%–81 % of the field measurements, while the ASHRAE model's estimates varied more widely, ranging from 33 % to 229 % of the measured values.

Impact of semi-empirical methods implemented in heat, air, and moisture (HAM) models on predicted wind-driven rain (WDR) loads and hygrothermal responses

The amount, duration, and intensity of wind-driven rain (WDR) are instrumental to the durability and sustainability of building components. Semi-empirical methods implemented in heat, air, and moisture (HAM) models have proved to be a practical and efficient approach to quantify WDR exposure of building components and to examine WDR's influence on hygrothermal responses of building envelopes. However, specific assumptions and simplifications in the implementations can cause discrepancies in WDR calculations and hygrothermal responses. While measured datasets or computational fluid dynamics (CFD) predictions are employed to validate WDR calculations in previous studies, few address the further influence on hygrothermal responses, particularly confronted with full-scale experimental datasets. This paper starts with a general formulation of semi-empirical methods for WDR calculation and elaborates the ASHRAE and ISO standards implemented in two representative HAM models, WUFI and DELPHIN. In the first phase of simulations, two full-scale experimental datasets at Leuven (Belgium) and Eindhoven (the Netherlands) are reproduced by the two models to compare predicted WDR loads. In the second phase, the predicted and measured WDR loads are imposed as boundary conditions of different scenarios of one benchmark case to further analyze the influence on the hygrothermal responses. The results indicate that both models roughly reproduce the semi-empirical methods. Because of disparity in algorithms and implementations and differences in weather and building conditions, the simulated WDR loads show similar trends with deviations to the measured datasets. The predicted hygrothermal responses show deviations to different extents, presumably due to disparity in WDR load predictions during certain periods.

Development of Prefabricated Additional Insulation Elements for the Renovation of High-Rise Apartment Buildings

Prefabricated additional insulation elements have demonstrated success in renovating up to 5-storey apartment buildings. However, the unique challenges posed by high-rise buildings necessitate a closer examination of installation and long-term performance. In this study, we developed an additional insulation element specifically tailored for renovating high-rise apartment buildings and analysed its hygrothermal performance. To test the performance of the insulation elements, we installed a prototype and measured its performance at critical points along the external envelope. We calibrated a calculation model and applied building performance simulation software to explore various combinations of prefabricated elements. Our goal was to compare the associated risks and the key hygrothermal properties of these different material combinations within the insulation element. Critical points between the insulation layer and the wind barrier, as well as between the surface of the existing concrete panel wall and the vapour control layer of the additionally insulated exterior wall were analysed. The study's results indicate that the thermal resistance and water vapour permeability of the wind barrier layer, and the presence of an appropriate vapour control layer primarily influence the performance and moisture dry-out of a structure. Additionally, the study results indicate that the weather component has a higher impact than in lower buildings as the wind-driven rain loads are considerably higher in the upper parts of the high-rise buildings. The initial moisture (w = 110 kg/m3 at the height of the 9th storey and w = 117 kg/m3 at the height of the 16th storey) dry-out can last more than 3 years depending on the building type and materials used. This study underscores the importance of tailored solutions and vigilant moisture safety management in high-rise apartment building renovations, particularly when utilizing prefabricated additional insulation elements.

Precipitation Simulation and Dynamic Response of a Transmission Line Subject to Wind-Driven Rain during Super Typhoon Lekima

Typhoons bring great damages to transmission line systems located in coastal areas. Strong wind and extreme precipitation are the main sources of damaging effects. Transmission lines suffered from wind-driven rain exhibit more susceptibility to damage due to the coupled effect of wind and rainwater. This paper presents an integrated numerical simulation framework based on mesoscale WRF model, multiphase CFD model and FEM model to analyze the motions of a transmission line subjected to coupled wind and rain loads during typhoon events. A full-scale transmission line in Zhoushan Island is employed to demonstrate the effectiveness of the proposed framework by simulating typhoon evolution in terms of wind fields and rainfall, solving the coupled wind and rain fields around the conductor and predicting the dynamic responses of the transmission line during Super Typhoon Lekima in 2019. The results show that the horizontal displacements of the transmission line under the joint actions of wind and rain increase approximately 17–18% compared to those of wind loads only. It is important to consider the coupled effects of wind-driven rain on conductors in the design of transmission lines under typhoon conditions.

Risk Evaluation Methodology for Weather-Related Degradation of Building façades

ABSTRACT Weather action is a relevant cause of façade degradation. Specific research evidence concerning its impact on the durability of building materials still needs to be comprehensively investigated and fully evaluated. This paper outlines a risk evaluation methodology for weather-related degradation of building façades. Two phases are considered: (1) laboratory work focussing on generic weather simulation in the wind tunnel in order to establish the hygric and thermo-aerodynamic vulnerabilities of constructions and to evaluate possible protective measures; (2) analysis of meteorological data and mapping of actual and projected hazards. Methods include the simulation and validation of wind-driven rain with gravimetric assessment of rainwater penetration into material specimens, the characterisation of the thermal behaviour of façades and that of the interaction between wind and building, using pressure measurements and flow visualization. The results enable decision-makers and professionals to evaluate the risk of weather-related degradation, individuating those areas of the construction more prone to damage, and thus to plan for adequate protection strategies. This would optimise the allocation of resources and increase the overall resilience of building structures. Future work is suggested with the intent of further validating the methodology both experimentally and with real-life applications.

US Consumers’ Awareness and Opinion of Boxwood Shrubs and Boxwood Blight

Boxwood blight is a significant threat to nurseries, garden centers, landscaping businesses, and homeowners, causing both financial and ecological damage. This fungal disease is primarily caused by two species, with Calonectria pseudonaviculata being the only reported casual species in the United States. The pathogen is spread by wind-driven rain, water splash, and contaminated plants, emphasizing the need for exclusion, sanitation protocols, cultural practices, and fungicides to manage its spread. Recently, efforts have shifted from containment to disease management, focusing on fungicide efficacy, diagnostic assays, and boxwood production analysis. Agricultural extension programs promote best practices to prevent disease introduction into nursery and landscape environments. Understanding consumer awareness and perceived risk regarding infestations is crucial as control measures evolve. In our Jul 2020 survey, which had 2795 completed responses from across the United States, we assessed consumer knowledge and opinions regarding boxwood shrubs and Boxwood light. The findings revealed demographic variations in awareness and opinions. Suburban residents were more aware of boxwood blight, whereas urban residents had a higher opinion of boxwood shrubs. From the tobit model, men were more likely to purchase boxwood compared with women despite knowing about blight, and Caucasians compared with non-Caucasians exhibited decreased liking for boxwood after seeing pictures of blight-infected plants. These insights can inform targeted communication strategies and assist consumers, vendors, and related industries in addressing the challenges posed by Boxwood blight. Further research into alternative plant preferences among consumers is also warranted for better development of boxwood blight management strategies.

The Impact of Wind-Driven Rain on Surface Waterproofed Brick Cavity Walls

Moisture ingress is a major cause of damage to masonry cavity walls. Products of various chemical compositions are available for wall surface treatment, aimed at reducing/eliminating water ingress. This study presents the results of full-scale wall tests designed to quantify water absorption into uninsulated and insulated brick masonry cavity walls exposed to wind-driven rain (WDR) with and without surface waterproofing. Two different waterproofing products were used: acrylic and silane–siloxane mixture. Untreated and treated walls were exposed to cycles consisting of 10 min wetting at 2.25 L/m2·min every 60 min. The results show that both treatments lead to a reduction in water ingress ranging from 90% to 97%. However, while a more consistent performance was obtained for the silane/siloxane-treated walls under repeated exposure, the results for the acrylic treatment were dominated by the original wall conditions, improved with a reapplication of the treatment. The testing protocol proposed in this study is effective in determining the performance of waterproofing treatments exposed to different levels of WDR. Both treatments prove to be effective in preventing moisture uptake in walls in moderate WDR exposure conditions, while in extreme WDR exposure conditions, the acrylic treatment is less effective.

CFD modeling of Wind-Driven Rain (WDR) on a mid-rise building in an urban area

Wind-Driven Rain (WDR) loading on building facades is a crucial factor for designing sustainable and climate-resilient buildings and preserving historical buildings. WDR loading on buildings has been studied previously but results for such a multi-parameter problem are not generally conclusive. Thus, the relevant provisions of ISO semi-empirical model cannot be applied with confidence for complex building configurations, such as those in urban areas given that the estimated WDR can be more than twice of the field measurements. This paper aims to evaluate the effectiveness of two WDR techniques, namely Lagrangian Particle Tracking (LPT) and Eulerian Multiphase (EM), combined with the steady-state standard k-ω RANS turbulence model (referred to as RANS-LPT and RANS-EM). The results obtained from the RANS-EM approach are compared with the RANS-LPT results reported in the literature for a six-story mid-rise residential building located in Vancouver, Canada. The study considers 13 distinct rainfall events, including stand-alone and urban area configurations with and without overhangs. The RANS-EM and RANS-LPT approaches are evaluated by comparing modeled wind and WDR against wind-tunnel and on-site WDR measurements, respectively. The study found that the RANS-EM requires less computational time and provides more accurate results for the test building situated in an urban area compared to the RANS-LPT.

GIS-based application to calculate directional wind-driven rain exposure on residential buildings at an urban scale: The case study of Zaragoza, Spain

Rainwater penetration is a key risk factor for the durability, hygrothermal performance, and habitability of built environments. Rainwater deflected by wind action (wind-driven rain, WDR) constitutes the primary source of water penetration for building facades. Therefore, characterizing their exposure to WDR is essential to have information that substantiates decision-making. However, this exposure has not yet been characterized at extensive urban scales. This research proposes an automated and replicable GIS-based method to assess the directional WDR exposure at a comprehensive urban scale. The method is based on the analysis of cadastral data and hourly weather records of rainfall intensity and wind velocity gathered over ten years. The directional WDR exposure throughout a mid-size European city (Zaragoza, Spain) is characterized as a case study. The detailed maps show that the WDR exposure ranges from 45.95 to 285.77 (mm/yr) between the different facades of the city. This variability in the built environment, caused by factors such as the urban configuration, local topography, and height and orientation of each facade, confirms the need for a functional urban characterization of WDR exposure. The proposed method can contribute to providing an automatized data-driven urban analysis to better establish urban strategies and renewal policies at different scales in cities, allowing for improving the resilience of the built environment against rainwater penetration.

Component-based hurricane vulnerability model for mid/high-rise commercial residential buildings

This paper focuses on the vulnerability of residential mid/high-rise buildings (MHRB) to hurricane-induced wind and wind-driven rain ingress, with a special emphasis on interior and contents damage. A component-based methodology utilizes the physics of rainwater ingress, distribution and propagation to provide the basis for the proposed MHRB risk assessment model. The model combines estimates of wind speed, impinging rain and surface run-off wind driven rain, envelope defects and breaches, interior water distribution and propagation, and component cost analyses to project envelope, interior and contents damage. The paper describes the model, verifies that it satisfies logical relationships to risk, and compares it against existing MHRB models. The new physics-based interior and contents vulnerability model should facilitate the evaluation of the cost effectiveness of mitigation measures.

THEORETICAL AND METHODOLOGICAL ASPECTS OF CLOUD WATER INTERCEPTION

Cloud water interception (CWI) occurs when water contained in fog and wind-driven rain collides with vegetation, merges into larger droplets, and precipitates to the ground. CWI has an important function as an additional source of water and its relationships with tropical cloud forests have often been emphasized. Despite its importance, there is no standardization of measurement methods, nor of the terms that designate the process in Portuguese. Therefore, a systematic analysis of research on CWI is necessary. To this end, the present study carried out a review of the theoretical and methodological aspects of CWI through description and analysis of terminology; history and chronology of studies on the topic; survey of the environmental conditions necessary for the CWI process to occur; analysis of methodological aspects relating to the measurement of CWI; and synthesis and discussion of magnitudes described in scientific literature. As a result, of the 31 publications reviewed, 14 different words were found, the most common being “Cloud Water Interception” (19.4%) and “Fog Drip” (16.1%). In general, CWI is more common in places such as continental edges and islands that are constantly subject to sea breezes. In most cases, the below-canopy measurement approach can be considered more accurate than those obtained by fog collectors. CWI is on average responsible for 42% of effective precipitation (n:41). The values listed show a large variation, between 0.5% and 462%, probably due to the different environmental characteristics of the sampled locations as well as variations in sample sizes.

Assessment of wind-driven rain (WDR) on buildings in an urban area: comparison of different CFD frameworks

The study of Wind-Driven Rain (WDR) loading on building facades is essential to design more sustainable and climate-resilient buildings, as well as to prevent further damage to old and historical buildings. Both WDR loading on buildings and façade responses to impinging raindrops have been studied previously but results for such a multi-parameter problem are not generally conclusive. Thus, the relevant provisions of ISO semi-empirical model cannot be applied with confidence for complex building configurations, such as those in urban areas since the WDR prediction can be more than twice that of the experimental data. In this paper, the Eulerian Multiphase (ME) technique is coupled with the RANS model to simulate the WDR loading on a six-story building under steady rainfall event conditions. Wind and WDR results are compared with the available wind-tunnel and on-site field measurement results, respectively. The field measurements were carried out on a six-story mid-rise residential building, located in Vancouver, Canada. The results show that the Euler-Euler framework (RANS-EM) predicts wind and WDR in such an urban area configuration more rapidly and accurately compared to the more traditional Euler-Lagrange framework (RANS-LPT) for both stand-alone and urban area configurations.

Wind-driven rain load in Finland in present and future projected climates

The amount of wind-driven rain (WDR) has been shown to have a major effect on the different deterioration mechanisms of outdoor exposed structures. For example, in recent studies of Finnish existing concrete element buildings the amount of WDR has been shown to have strong correlation with the corrosion rate of reinforcements in carbonated concrete and the freeze-thaw damage of concrete. The latter can be related to all porous stone-based materials (e.g., bricks and mortars). In addition, the amount of WDR has a major effect on mould growth potential in different materials or structures sensitive to it. Thus, the effect of the amount of WDR in present climate has been studied comprehensively. In this study, the amount of WDR is calculated for a new 30-year period (1989-2018) presenting the present climate among with two future periods presenting 2050 and 2080 climates. In future climate projections, three different CMPI5 based scenarios are used: RCP2.6, RCP4.5 and RCP8.5. All calculations take into account the wind directions and they are made for four different locations presenting Finland: coastal area, southern Finland, inland and northern Finland (Lapland). Based on the results, the WDR load in the form of rain or sleet is increasing in all locations and from every direction regardless of the used scenario. The highest relative increase is in inland and Lapland, though, the load is still significantly higher in coastal and southern parts of Finland. With all the scenarios the WDR load is still focusing on southern directions, but it will be more evenly divided for other directions than in present climate. In addition, the WDR load is increasing during autumn and wintertime, i.e., during the periods when in the latitudes the drying conditions are weak because of the lack of solar radiation and the high-level relative humidity.

Wind-driven rain tightness of building-integrated photovoltaics panels

The exposure to wind-driven rain (WDR) is a key factor impacting the performance and the durability of the building envelope. Building-integrated photovoltaic (BIPV) panels are increasingly used as roofing and façade materials, but little information is available on their weather protection performance. Although WDR exposure has been qualitatively investigated in laboratories, only few studies have directly quantified the water intrusion through BIPV. This article presents the results from a WDR laboratory test of a BIPV product, where water intrusion was both qualitatively and quantitatively investigated. Furthermore, as roof integration is the primary function of the studied BIPV panels, the results from the same test performed on another traditional roofing material, i.e., concrete tiles, are described and discussed. The test results showed that the BIPV panels performed better as façade cladding than as roofing material, since no quantifiable water leakages were detected at 90° inclination. At 15° and 30° inclinations, the total water leakages through the BIPV system were around 90% lower than those of the concrete tile roofing. This article’s findings demonstrate that the quantification of water intrusion through BIPV panels is feasible and can provide significant information for further developing and improving the design of BIPV systems as climate screens.

Hygrothermal Performance of Prefabricated Insulation Elements for Serial Renovation of Apartment Buildings in a Moderately Continental German Climate

The reduction of energy use in the buildings is expected to be reached by fulfilling several requirements of the low- and nearly-zero energy buildings (nZEB) policy. The improvement of the energy performance of the building envelope and the service systems of the existing buildings offers great potential for energy savings as the annual replacement of the existing stock is only 1 to 2%. The efficient way to accomplish the purpose and global goals of the nZEB is to apply the integrated design process, development, and application of prefabricated insulation elements on a large scale. In this project, in the Berlin area of Germany, prefabricated timber frame insulation elements were designed for the external insulation of the envelope of the apartment building in the serial renovation process, with the thermal transmittance of the external envelope U external-wall = 0.14–0.16 W/(m2·K). In the current study, the potential hygrothermal risks and their effect on highly insulated multi-story apartment building envelope were analyzed. The study contained a set of hygrothermal analyses to ensure the moisture safety of highly insulated facade structures and the selection of materials from the perspective of hygrothermal performance and low risk of degradation. This research found that the risk of mold growth is high if timber elements are installed without protective measures against drying-out built-in moisture, wind-driven rain, and other weather conditions. The initial moisture content of the external concrete slab, to be considered critical, is 90 kg/m3, and the drying out period is longer than the covered with new layers constructions can sustain if a proper vapor control layer is not added between the existing moist wall and installed insulation elements. Furthermore, the wind barrier layer with high thermal resistance and vapor permeability of the installed insulation element helps to minimize the risk of mold growth. A careful analysis and selection of materials allow to design moisture-safe timber frame insulation elements and provide low thermal transmittance of renovated building envelopes. The results showed that before the final design and installation of the insulation elements, a thorough hygrothermal analysis of the original external envelope with actual climatic conditions and moisture loads must be realized.

Impact of different water penetration criteria and cavity ventilation rates on the risk of mold growth in timber frame walls with brick veneer cladding

The present paper investigates the impact of different water penetration criteria on the risk for damage in a common type of building envelope in Nordic countries, timber frame walls with brick masonry veneer. The studied walls are evaluated based on one damage criterion, the risk of mold growth. The study investigates several parameters: water penetration criterion, type of moisture source (uniformly distributed or point source) and its position in the wall assembly, air change rate (ACR) (representing different workmanship scenarios), wind-driven rain (WDR) coefficient, and locations (Gothenburg and Rensjön, with different average annual rainfall and temperature). Two criteria on how to implement water penetration are compared: a) a commonly accepted reference model that assumes one percent of all wind-driven rain deposited on the façade to penetrate the clay brick cladding, and b) a new criterion stating that 3.8% of WDR penetrates when the water content of the brick veneer cladding is above 90% of its saturation capacity. The simulation is done for a thirteen-year period with WUFI Pro and WUFI 2D. The results indicate the greater importance of implementing water penetration compared to ventilation in cavities. Further, the findings suggest that the moisture source’s location significantly impacts the mold growth risk. The results also show that the choice of the WDR coefficient affects the risks, which suggests that this factor needs accurate quantification for hygrothermal analyses. The results in this study suggest that an effective measure for the design/maintenance of such walls should incorporate: a) limiting the amount of water penetrating through the cladding, particularly stopping water from reaching the sensitive elements, i.e., timber studs, b) removing extruded mortar stemming from poor workmanship, if any, which may act as a capillary bridge.

Closing the gap between traditional wind-driven rain studies and the performance-based design of building façades: Case study of the Netherlands

Over the last few decades, analyses of wind-driven rain exposure on building façades have been conducted in multiple regions. Sometimes, these studies also included the driving rain wind pressure, thereby characterising both critical factors contributing to rainwater penetration into façade materials. However, practitioners typically rely on performance results obtained from standardised watertightness tests to make façade design decisions, even though these tests do not recreate the specific exposure combinations that can occur on each façade. Consequently, there is no quantitative correlation between the traditionally identified exposures and actual façade designs, resulting in pure qualitative choices and poorly optimised designs. This study addresses this issue by correcting the existing methodological deficiencies in a prior calculation procedure, which aims to relate the exposure parameters that the façade configuration withstood during any watertightness test to the expected climate exposures at its design operating conditions. New contributions are presented to enhance the method reliability as well as to reduce calculation effort and reliance on exhaustive weather data. The various climate parameters required to establish this relationship were analysed and tabulated for the Netherlands, enabling a truly performance-based design of façades to resist rainwater penetration throughout the country. Different methods of implementing this procedure, according to the availability of weather data, were also compared for façade case studies located in Amsterdam and Maastricht.