Moisture Problems Research Articles

Meeting the challenges of structural damp diagnosis in older buildings

Diagnosing dampness in the walls of buildings that were constructed 100 years or more ago, often using materials and techniques that are very different from those in use today, can be extremely challenging. Despite the availability of a wide range of diagnostic equipment aimed at identifying building dampness, there is no single piece of diagnostic equipment currently available capable of overcoming the wide natural variations found in the field, that is able to reveal excess moisture within structures, and equally importantly, to determine its severity. All too often, damp in walls is misdiagnosed by over-reliance on a single piece of equipment. This equipment often appears to have been designed on the assumption it will be used on buildings constructed from currently available standard materials, which have been assembled using conventional techniques to meet current regulations. However, when using electronic meters to diagnose damp, if multiple measurements are taken using different types of meter, it is possible to overcome most of the limitations of individual meter types along with any tendency to misrepresent the moisture status of older or less common building materials. This paper outlines a method of damp diagnosis for historic and vernacular walls that allows multiple readings, taken with three complementary meter types, to be combined and mapped back onto the building. This method highlights the differences between raised salts and true excess moisture, together with their respective severities and spreads, leaving the surveyor free to apply his/her knowledge of materials science and building construction to identify the most likely causes of any problems revealed and, if necessary, to devise remedial strategies that are compatible with the building. Three examples illustrate how the method outlined can be successfully used on buildings with very different moisture problems.

Prediction evaluating of moisture problems in light-weight wood structure: Perspectives on regional climates and building materials

Most of the construction techniques and materials used in Korean wooden houses are based on those used in North America and Europe. In order to prevent moisture problems in wooden houses, it is necessary to evaluate the hygrothermal behavior of the building envelope. In this study, the hygrothermal performance of light-weight wood structures was analyzed using the WUFI simulation program in 20 regions of Korea. As the results, since there is a clear distinction between summer and winter in Korea, the location of the vapor resistance materials should be considered, and the 2 × 6 structure was found to be the most stable for installing the vapor retarder and the weather-resistive barrier on the inside and outside of a wall. In addition, the water stability of the light-weight wood structure was affected by the hygrothermal climatic conditions in each region. The OSB surface is influenced by the amount of driving rain, but the vapor-retarder layer is more significantly affected by summer heavy rain. Therefore, consideration of the regional climate conditions, the hygrothermal properties of building materials, and the location of building materials are needed to ensure the water stability of the walls in the light-weight wood structures.

Moisture risk assessment of cross-laminated timber walls: Perspectives on climate conditions and water vapor resistance performance of building materials

Cross-laminated timber (CLT), an engineering wood material prepared by bonding lamina in a vertical direction, is actively used in roofs, floors and shear walls of residential and commercial buildings, owing to its excellent structural stability, insulation performance, among other advantages. The building envelope, to which the wood-based material is applied, should be designed to prevent moisture problems. In this study, the ply-lam CLT with plywood was prepared, and its hygrothermal properties including the thermal conductivity, water vapor resistance factor, specific heat capacity, bulk density, and porosity were analyzed. A small-scale test demonstrates the feasibility of hygrothermal behavior evaluation of the wall with ply-lam CLT by numerical simulation. Moreover, the moisture risk of the ply-lam CLT house walls was evaluated by analyzing the climate conditions of 20 major cities in Korea. The moisture risk assessment results imply, that to ensure water stability, the envelope should be designed considering the type of insulation material, its hygrothermal properties, thickness, climate conditions of the area, etc.

Analysis of the improved water-resistant properties of plaster compounds with the addition of plastic waste

The aim of this article is to analyse the water-resistant properties of gypsum compounds with plastic cable waste added in order to determine the suitability of their use as an alternative to combat moisture problems in buildings. In the experimental process, test samples were made and subjected to capillary water absorption, water vapour permeability, wet chamber, water-stove cycle and total water absorption tests, and their porosimetry was also studied using the mercury porosimetry test. The results showed a significant decrease in water absorption and retention capacity. This is due in part to the reduced pore volume of the compounds that is achieved without affecting the hygrothermal properties of the gypsum products and keeping their mechanical properties above the minimum values indicated in the regulations. Thus, the material studied is a good alternative to the gypsums currently available on the market to be applied in the areas of buildings most exposed to water and it contributes to reduce environmental impacts.

Towards upgrading strategies for nZEB-dwellings in Norway

Recent work suggests that upgrading in line with the Norwegian building regulations or by upgradingto the requirements of the national passive house norm, NS3700, can enable nZEB level to be achieved.The aim of this work is to explore the typical Norwegian housing typologies and some importantcharacteristics of the building envelope for these houses from different decades. The exploration involvedsurveying the typical technical qualities of Norwegian housing and how these have evolved – providingan important foundation to work addressing strategies and methods for upgrading dwellings to nZEBlevel in the next phases of the ongoing research project. The results of this work show that the buildingnorms and practices developed throughout the years have made dwellings more moisture resilient, withan increased drying-out potential through mechanical ventilation, control of the air change rate and theuse of more vapour-open wind barriers in the building envelope. Based on this, the work to follow willsuggest strategies for upgrading to nZEB level, solutions for upgrading building envelope componentsto high performance level and a methodology for risk reduction of moisture problems in the upgradeddwellings from the different decades.

Field study of hygrothermal performance of highly insulated wood-frame walls under simulated air leakage

Climate change has led to governments mandating greater energy efficiency in building codes throughout Canada and the US. Increased energy efficiency requires a high level of insulation of the building envelopes, which may introduce unintended durability concerns. To investigate potential durability issues, six types of high thermal resistance (High RSI) wall assemblies were tested at a building envelope test facility. This study compares the hygrothermal performance of conventional 38 × 140 mm framing (i.e. baseline wall) with three types of deep cavity walls and three types of exterior insulated walls. The wall assemblies tested have an average installed thermal resistance of RSI 6.8 and they were installed at both north and south-facing orientations of the building envelope test facility to observe their relative performance. The hygrothermal conditions of test walls were monitored under three consecutive periods: baseline period without air leakage in fall/winter time, air leakage period with air injection in winter/spring time, and drying period without air leakage in spring time. The hygrothermal performance in terms of moisture content profile of OSB sheathing and mold growth risk at the interior surface of OSB sheathing was analysed with respect to wall types and orientation. The exterior insulated walls had lower moisture content than deep cavity walls and the baseline wall throughout the whole monitoring period, and there was no condensation or mold growth risk under simulated air leakage. Although the deep cavity walls had higher moisture content levels than the baseline wall, they were less responsive to air leakage than the baseline wall due to the hygroscopic characteristics of cellulose fiber insulation installed in the stud cavity. The deep cavity walls had higher risk of moisture problems than the baseline wall and the exterior insulated walls.

Implementing post-occupancy evaluation in social housing complemented with BIM: A case study in Chile

This study reports a Post Occupancy Evaluation performed on a social housing complex consisting of 400 apartments, in which symptoms and damage produced by high moisture levels needed investigation. The resulting knowledge is of special interest for other projects designed to be mass-produced such as social housing. Large costs for repairs can be reduced by applying measures to avoid moisture problems in indoor environments. The evaluation was performed over three stages, indicative, investigative and diagnostic. The process was mapped and the data stored using BIM standards so it can be used by stakeholders to take further actions. In the indicative stage, data was collected through questionnaires and surveys, and a quick evaluation was conducted of the affected units. In the investigative stage, an analysis of the entire building complex was conducted through simulation and tested against the building energy standards. In the diagnostic stage, in-situ and laboratory measurements were made and used for calculations. The results show that many factors were involved in the moisture damage, whose main causes were overcrowded spaces, inadequate thermal regulation for the local climate, poor apartment and complex design, and flaws and inconsistencies in the quality of construction.

Wall finishing materials and heritage science in the adaptive reuse of Jakarta heritage buildings

Given its tropical setting, moisture problems are inherent issues found in walls of heritage buildings in Indonesia that require replacement of wall finishing materials with specific properties. This is where heritage science becomes an important approach in the creation of plasters and paints that best resemble its original and/or provide better performance through innovations. Heritage science possesses great potential in improving evidence-led conservation work in Indonesia by incorporating properties of traditional materials with present technology for cultural sustainability that is gaining urgency in the midst of burgeoning population growth. However, despite its growing application for historically significant heritage buildings, the need for preliminary scientific testing is not commonly acknowledged and applied in the adaptive reuse of small-scale heritage buildings in Indonesia. Therefore, this paper studies two UNESCO-funded pilot projects in Jakarta and tracks the role of heritage science throughout their conversion, and aims to evaluate the constraints, by conducting literature studies and eight interviews with various stakeholders involved. It is found that heritage science is yet a key player in Indonesian conservation works, however, it helps uncover material properties of wall finishing materials that best tackle moisture problems in Jakarta heritage buildings.

Evaluating the potential of freeze-thaw damage in internally insulated masonry under climate change using different models

To mitigate the effects of climate change, higher insulation levels in buildings are mandated by the National Energy Code for Buildings. However, increased insulation levels within building envelopes may lead to a greater risk of moisture problems. With a changing climate, higher rainfall intensity, stronger winds and more storms are expected, which may increase wind-driven rain loads on façade and risks for rain penetration damages of building envelopes. This paper aims to present results of the effects of climate change on the freeze-thaw damage risk of internally insulated brick masonry walls of buildings in different Canadian cities, using different freeze-thaw models. Freeze-thaw damage was evaluated using different freeze-thaw models. Simulations were performed using DELPHIN 5.9.4. Results showed potential risk to freeze-thaw in Montreal and Vancouver after retrofit. Under climate change, Winnipeg has the lowest risk to frost damage, though damage functions showed an increase in the level of severity. Comparing the results of different models under a changing climate, the damage functions seemed in a good agreement for most of the cases, except for the Indicative Freeze-Thaw Cycles (IFTC) evaluated in St-Johns. This model counts the number of freeze-thaw cycles based on short duration of freezing and thawing and therefore does not consider longer freeze-thaw period.

Hygrothermal simulation assessment of internal insulation systems for retrofitting a historic Danish building

The built environment is accountable for 1/3 of the European energy consumption. Thermal insulation is a key factor affecting the energy performance of buildings. Historic buildings typically were made with solid external walls of brick masonry or natural stone, rarely insulated afterwards. Often the buildings have worth-preserving façades making internal insulation the only feasible technique, however significantly modifying the hygrothermal performance of the façade. The research objective of this paper is to simulate the hygrothermal performance of solid masonry walls in an old Danish hospital that will be internally insulated following the Danish requirement (U-value) for external walls (change of use of buildings) and transformed into dwellings, involving different insulation systems. Heat loss and masonry moisture content level after adding internal insulation and the possible effects of hydrophobization on the moisture content is simulated. Simulations show an increased moisture content in the original wall when adding internal insulation implying an increased risk for moisture-related damage (mould growth, frost damage and interstitial condensation). The results also show that hydrophobic impregnation of the internally insulated facades may be vital in avoiding moisture problems and securing a moisture-safe energy renovation of buildings like the one studied.

Analysis of walls of functional gypsum board added with porous material and phase change material to improve hygrothermal performance

Gypsum board is widely used as a finishing material, and it is mixed with functional materials to improve the comfort level of indoor air, provide thermal insulation, and satisfy moisture properties. In addition, Phase change material (PCM) is also used as a functional material to reduce energy consumption. Recently, there have been many studies on improving moisture problems, such as condensation and mold growth. Therefore, the hygrothermal behavior of building materials must be carefully considered to reduce the risk of moisture problems. The objective of this study was to improve the thermal and moisture performance of gypsum board, and achieve energy savings by adding porous material and PCM. The characteristics of functional gypsum board (FGB) with expanded vermiculite (EV), expanded perlite (EP), nano carbon material (C300), and n-octadecane (PCM) were analyzed by fourier transform infrared (FTIR) spectroscopy for structural stability. The thermal conductivities of the various FGBs were analyzed by TCi thermal conductivity analyzer, and their hygroscopic properties were analyzed based on ISO 12,571 and 12,572. In addition, the hygrothermal performance of walls applied with FGB was evaluated using Wäme und Feuchte instationär (WUFI) simulation; the wall composition was concrete wall. As a result, the thermal conductivities of FGB were decreased by 15%, compared with the conventional gypsum board. In the case of moisture properties, the water vapor resistance and water content of FGB were increased, compared with the conventional gypsum board (SR). However, the simulation results showed that there were no moisture problems, such as condensation, mold growth, or structural damage.

Stochastic modelling of hygrothermal performance of highly insulated wood framed walls

As energy consumption has become an important issue in building design, most building codes require a higher insulation level for building envelopes to improve the building's energy efficiency. However, the highly insulated walls may lead to a higher risk of moisture problems. Although hygrothermal simulation has been widely used to investigate the moisture performance of wood framed walls, the uncertainties of input parameters such as material properties, boundary conditions and moisture loads, may lead to discrepancies between simulation results and actual performance of the envelope. This paper investigates the hygrothermal performance of highly insulated wood framed walls using a stochastic approach, which combines the Latin Hypercube Sampling method and Factorial Design to take into account the uncertainties of material properties, boundary conditions and moisture loads (air leakage and rain leakage). The investigated walls include an I-joist deep cavity wall, two exterior insulated walls, and a conventional 2 × 6 stud wall as the baseline. It is found that under the moisture loads introduced (i.e. air leakage and rain leakage), the exterior insulated walls have a lower mold growth risk than the deep cavity wall and the 2 × 6 stud baseline wall. The uncertainties of material properties do not result in significant variations in simulation results such as moisture content and mold growth index as uncertainties of moisture loads do. The hygrothermal performance of these highly insulated walls is more sensitive to moisture loads and the significance of the moisture loads (air leakage and rain leakage) depends on climatic conditions.

Combination of Diagnostic Tools for the Proper Identification of Moisture Pathologies in Modern Residential Buildings

A study of moisture pathologies in a modern residential multifamily building is presented. The housing block was designed under the regulation NBE-CT of 1979 in northern Spain. After the appearance of some moisture problems in the façades, three complementary studies were conducted to analyze the situation of the envelope and diagnose the best improvement possibilities. First, indoor conditions of temperature and humidity of the apartments with moisture pathologies were monitored. During 40 winter days, the occupancy, heating operation, and natural ventilation were analyzed. Second, the inner and outer surface temperatures of the studied façades were measured. Thermal insulation degree, thermal capacity, and thermal bridge effects were measured to assess the risk of interstitial condensation under the real conditions of use. Third, an infrared thermographic survey was carried out, which allowed the detection of irregularities and the assessment of moisture problems. The wrong interpretations, which would have been made if the complementary studies had not been done, are exposed. The key towards the accurate diagnosis was the combination of tools. Finally, some technical solutions based on ventilation or thermal insulation enhancement are proposed as different ways to reduce the high levels of relative humidity indoors and minimize the risk of condensation in the future.

Can Increased Endotoxin Levels in House Dust be used as an Indicator of a Mould Problem?

Endotoxins are common indoor biocontaminants. Our purpose was to investigate the association of endotoxin content with mould problems in house dust in buildings, to determine whether endotoxins can be used as an indicator of the presence of moulds in buildings. The participants were selected from the Clinic for Indoor Air Health Problems on the basis of symptoms attributed to indoor air problems. We examined their health status. House dust was collected in new vacuum cleaner bags from surfaces in the rooms of their homes or workplaces. We measured the endotoxin concentrations in the house dust of 13 homes and 9 workplaces of the 19 participants, using a quantitative limulus test. The median endotoxin concentrations in the house dust of their homes was 9.9, and the range was 1.9–103 EU/mg; and in the house dust of workplaces it was 4.5, and the range 0.5–81 EU/mg. We found higher house dust endotoxin concentrations in rooms in which moisture problems had been identified or in dwellings in which pets were kept. Our pilot study suggests that endotoxins may be a useful additional tool for estimating possible mould contamination at homes or workplaces.

Combined application of GPR and ERT for the assessment of a wall structure at the Heptapyrgion fortress (Thessaloniki, Greece)

Non-destructive investigation of monuments can be an extremely valuable tool to evaluate potential structural defects and assist in developing any restoration plans. In this work, both Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT) techniques were applied to a tower wall of the Heptapyrgion fortress located in Thessaloniki, Greece, which was facing significant moisture problems. GPR cross sections, mainly obtained with a 500 MHz centre frequency antenna, and ERT profiles were collected along the same survey grid on the tower wall. The gprMax numerical solver was used for the GPR forward modelling. In addition, an auxiliary program was used to design and import into gprMax complicated structures and this allowed to simulate more realistically the wall defects and moisture. The GPR simulator was used to assess and optimize the field data acquisition and processing parameters, and to assist in interpreting the GPR cross sections. The ERT sections were inverted as individual 2D lines and also, as a full 3D dataset. The final GPR and ERT data were jointly interpreted in view of the studied problem as results of both methods are highly correlated. A high moisture content area at the eastern part of the wall was identified in both GPR and ERT data, along with the interface between different phases of construction. Through the GPR data we were also able to delineate possible structural defects (cracks, small voids) which was not possible with just using the ERT data. Furthermore, a very good matching was evident between the simulated GPR modelling results incorporating field-interpreted features, and the actual field GPR results, thereby validating the proposed data interpretation. The overall survey and modelling approach produces results that are in a very good agreement between them and proved very useful in accessing the wall structure.

Influence of envelope properties on interior insulation solutions for masonry walls

Energy efficiency in historical buildings with a worth-preserving appearance can be improved with interior thermal insulation. However, interior thermal insulation may change significantly the hygrothermal performance of the building envelope and increases the risk of moisture problems in the assembly components. This paper studies the influence of different wall structures, types of exterior render and brick and vapor control strategies on the moisture performance of internally insulated walls with vapor-open insulation for different climatic conditions in Switzerland. The hygrothermal performance is simulated with a coupled heat and mass transport model and evaluated using a hygrothermal indicator, called the RHT Index. The numerical analysis indicates that the hygrothermal performance of interior insulated walls depends mainly on the moisture performance of the exterior finishing render. A capillary active render with larger liquid permeability leads to higher moisture contents in the building envelope. The influence of parameters such as masonry structure and brick type on envelope hygrothermal performance is rather small. For wall envelopes with less capillary active renders, the need to use a vapor barrier depends on the risk for water leakage and the vapor resistance of the render.

Field measurements of hygrothermal performance of attics in extreme cold climates

Attic ventilation is typically recommended for the removal of moisture build-up caused by air leakage from indoors in cold climates, however, it may also increase the amount of snow and rain penetration into the attic, especially in the extremely cold climates. In northern regions, extremely cold temperatures can cause snow particles to become very fine, which will penetrate vents or unsealed openings. The snow accumulated in the attic would melt at temperatures above zero and penetrate to indoors through the ceiling and cause moisture problems. One of the solutions is to add filter membranes along a ventilation cavity behind the façade to prevent snow from entering the attic. The ventilated attics with filter membrane had some success but there were instances with reported water leakages and moisture damages. There have been also attempts to use un-ventilated cold roofs. Un-ventilated attics prevent snow accumulation but do not allow for effective removal of moisture, which could be risky and prone to moisture damages.This paper presents a field study of the hygrothermal performance of three attic venting systems. Three houses with different attic designs built in Canadian North were monitored: two with a ventilated attic but different strategies controlling snow entry and one with an un-ventilated attic. Measurements show that the ventilated attics had acceptable conditions. The moisture content of wood structure at most monitored locations in the un-ventilated attic remained above 20% through the summer, which indicates that without ventilation the construction moisture and moisture accumulated through winter cannot be effectively removed.

Ventilation Positive Pressure Intervention Effect on Indoor Air Quality in a School Building with Moisture Problems.

This case study investigates the effects of ventilation intervention on measured and perceived indoor air quality (IAQ) in a repaired school where occupants reported IAQ problems. Occupants’ symptoms were suspected to be related to the impurities leaked indoors through the building envelope. The study’s aim was to determine whether a positive pressure of 5–7 Pa prevents the infiltration of harmful chemical and microbiological agents from structures, thus decreasing symptoms and discomfort. Ventilation intervention was conducted in a building section comprising 12 classrooms and was completed with IAQ measurements and occupants’ questionnaires. After intervention, the concentration of total volatile organic compounds (TVOC) and fine particulate matter (PM2.5) decreased, and occupants’ negative perceptions became more moderate compared to those for other parts of the building. The indoor mycobiota differed in species composition from the outdoor mycobiota, and changed remarkably with the intervention, indicating that some species may have emanated from an indoor source before the intervention.

Selected problems of protection of historic buildings against the rainwater and the groundwater

The paper presents selected problems in the selection of the state of the art modern civil engineering solutions for drying moisture or wet, in particular parts of the underground structures of the brick historic buildings. The repair works of the immobile cultural heritage civil engineering objects require the appropriate choice of the design solution. These should be achieved by obtaining the assumed effects in the form of the effectiveness of repairs regarding all possible measures of protection of the cultural heritage buildings. Another key issue of the analysis of the causes of moisture formation in underground masonry structures is the necessity of consideration of the historic character of these buildings. Based on authors' extensive experience and expert knowledge, a range of diagnostics process as well as the assessment of the causes of the moisture problems of historic buildings for several selected cases was proposed. Moisture is transferred from the outside of the building to the basement interior by four mechanisms liquid water flow, capillary suction, vapor diffusion and air movement. The variety of the different mechanisms of moisture transfer, especially regarding buildings of cultural heritage implies that the selection of the most suitable system solution for solving moisture problem is the most crucial and a key issue in a specific case.

Evaluation of the infrared thermography technique for capillarity moisture detection in buildings

Moisture problems are very frequent in buildings and, in most cases, are only visible when they are in advanced stages, thus causing financial losses and damages, and presenting difficulties for repairing to owners. Among nondestructive tests available in the market, infrared thermography has the capacity to be applied for this type of problem, since it can identify hidden problems and inspect large areas besides being fast and easy. In this sense, this article is intended to verify infrared thermography applicability for moisture detection by capillarity in buildings. Work methodology was developed through inspection of a building that presented evident signs of moisture by capillarity as well as potential development of this type of problem. Inspections were carried out during rainy season, when this type of manifestation develops the most. During test period, it was possible to verify that infrared thermography can accurately detect areas affected by humidity. However, it does not provide any information about problem severity. The thermal gradient between affected and intact areas may indicate the best inspection times -which occur when these values are at the highest level- as well as times not suitable for this activity. Despite finding failures, thermography presents many limitations, as it is influenced by environmental conditions, inspection schedule and the type of material where an issue takes place.