Introduction
Moisture, in all its physical forms, is commonly regarded as the single greatest threat to durability and long-term performance of the housing stock Excessive exposure to moisture is not only a common cause of significant damage to many types of building components and materials, it also can lead to unhealthy indoor living environments Some of the more serious effects resulting from moisture problems in houses include:
• decay of wood and corrosion of metals
• infestation by termites, carpenter ants and other insects
• negative impacts on indoor air quality
• the growth of mold, mildew and other biological contaminants
• reduced strength in building materials
• expansion/contraction damage to materials
• reduced thermal resistance of wet insulation
• premature failures of paints and coatings
• negative effects on building aesthetics
There is wide agreement that successful management of moisture in its various forms is essential for houses to be durable, safe, and energy efficient
The Partnership for Advancing Technology in Housing, a collaborative initiative between the U.S Department of Housing and Urban Development and private organizations, has sponsored a comprehensive study on moisture-related issues affecting the durability of U.S housing stock This research focuses on water problems caused by leaks, condensation, and water vapor in single-family, detached houses of conventional light-frame construction, particularly in continental U.S climates The study's scope encompasses houses of all ages, with occasional references to multifamily low-rise buildings and alternative construction methods like SIPS and steel framing, excluding extremely cold or hot climates and flood-related water damage.
The primary objective of the project is to devise a comprehensive set of research recommendations aimed at mitigating moisture-related issues in housing, thereby preventing or resolving such problems Through an exhaustive review of existing technical literature on bulk water and water vapor issues in housing, as well as their corresponding solutions, the research recommendations were formulated Supplementing the literature review, expert insights were gathered through interviews with practitioners and researchers, providing valuable information on field-observed problems and ongoing public and private research initiatives focused on moisture problems.
This report outlines key recommendations for future research, providing a comprehensive framework for organizing studies on moisture control and related issues A series of goals are identified, which serve as the foundation for categorizing and prioritizing potential research projects These projects, outlined in Sections 3, 4, and 5, are accompanied by a clear rationale and desired outcomes, offering a roadmap for future investigation and discovery.
Here is a rewritten paragraph that captures the essential meaning of the original text while complying with SEO rules:"Building moisture and durability projects require careful consideration of timing, effort, and sector involvement Drawing from literature and expert panel input, project concepts have been developed and prioritized, with some identified as 'very high' or 'high' priority The Expert Panel on Moisture Research provided valuable insights, shaping the direction of these projects and informing the allocation of resources By understanding the complexities of building moisture and durability, stakeholders can make informed decisions about project pursuit, whether through public, private, or collaborative efforts."
The report is supplemented by additional materials presented in three comprehensive Appendices, providing a wealth of information on moisture-related topics Specifically, Appendix A offers an in-depth review and analysis of existing literature, categorized into key sections on bulk moisture, water vapor, and moisture modeling Meanwhile, Appendix B furnishes summaries of ongoing research projects, serving as a valuable context for shaping the agenda for future work Furthermore, Appendix C outlines actionable recommendations for enhancing the coordination of research efforts among various groups focused on addressing moisture issues in housing.
Research Goals
Build Additional Knowledge about the Moisture Problem in Housing
Building moisture is a pressing concern that warrants a more comprehensive understanding, yet existing knowledge on the subject is largely qualitative, conceptual, or anecdotal A quantitative and authoritative analysis of the issue is essential to inform research and development (R&D) efforts, secure funding from various sources, and prioritize this problem among other competing concerns By providing a clear picture of the issue, stakeholders can effectively allocate resources across different areas of study under the broader umbrella of moisture management, ultimately driving progress towards addressing this critical challenge.
• Develop Reliable Quantitative Information Documenting the Nature, Frequency, Severity and Impacts of Moisture Problems in Housing This first goal is the most basic
Despite the significance of moisture problems in housing, there is a notable lack of quantitative data on their prevalence and relationship to design, occupant variables, age of the house, and geographic location Moisture issues such as roof and wall leaks, wet basements, and standing water in crawl spaces are common concerns, yet their frequency and economic impacts remain unclear Understanding the prevalence of these problems is crucial, but it is equally important to estimate their economic and non-economic consequences, including the costs associated with repairs, health effects, and overall quality of life.
Research has shown that moisture in homes is not just a structural issue, but can also have significant health implications for occupants, prompting a shift in focus from physical to health effects among organizations, the public, and the home building community However, despite growing awareness, major gaps in knowledge remain regarding the relationship between moisture and occupant health, highlighting the need for further scientific understanding to fully grasp the magnitude of the moisture problem Improving this understanding is crucial to addressing the health impacts of moisture in buildings and ultimately treating them as part of the broader spectrum of moisture-related issues By filling these knowledge gaps, we can better comprehend the relationship between moisture in homes and health outcomes, informing strategies to mitigate these effects and promote healthier living spaces.
Prevent and Correct Specific Moisture Problems
The central features of a sound plan for moisture research should be to minimize the impact of moisture on the built environment A great deal is already known in this area, much of it incorporated in building codes and standards as well as in rules of practice Yet there is reason to believe that problems arise when things are overlooked or communications fail, allowing moisture to accumulate in building environments that are susceptible to its effects
The general approach here is to strengthen various layers of protection or lines of defense There are four corresponding goals under this heading These goals reinforce one another and, in combination, have the potential to significantly reduce the incidence and detrimental impacts of building moisture They are as follows:
• Build in Moisture Protection through Proper Design and Construction Detailing The first line of defense against moisture problems is undoubtedly good design and the proper execution of design details that prevent moisture intrusion
Identifying improper work during the construction process is crucial to prevent costly corrections and ensure compliance with building codes By incorporating specific requirements into building codes and enforcing them through rigorous design review and inspection, defects can be detected and corrected before project completion Early detection and correction of improper work not only saves time and resources but also ensures the structural integrity and safety of the building.
• Detect and Correct Moisture Problems Before they Cause Serious Damage To the extent moisture problems do arise in spite of these measures, they should be caught and corrected quickly, before they can cause serious damage
To minimize the risk of moisture damage, it's essential to leverage new technologies that can detect and mitigate moisture-related issues promptly In cases where moisture problems persist, the final line of defense lies in utilizing building materials and systems that are engineered to be more resistant to moisture, thereby reducing the vulnerability to damage By incorporating these advanced materials and systems, property owners can significantly reduce the likelihood of costly repairs and ensure a safer, more durable structure.
Realize the Potential of Moisture Modeling Tools
Traditional approaches to preventing moisture problems have been based on rules of thumb and generations of field experience Over the last twenty years a wide range of moisture modeling software tools have become available, and shown great potential for improving building designs These tools now can model vapor diffusion, flows of humid air, bulk water intrusion, wetting, drying and moisture storage of different materials and phase change phenomena They can also deal with a growing number of building material and assembly types Note that models can be used in several ways, e.g to develop or test general design guidelines or requirements, to assess moisture vulnerabilities of specific designs, and to derive ideal material properties Note that some of these outputs will feed back into the previous goal of building in moisture protection through proper design and detailing Specific goals are as follows:
To achieve accurate moisture modeling, it's essential to address the data gaps that currently limit its precision The underlying physics of moisture modeling are well understood, but the accuracy of the model's output is heavily dependent on the quality of the input data Unfortunately, several key types of input data are poorly defined, leading to ambiguity and uncertainty in interpreting the modeling results, which can significantly impact the reliability of the model's predictions.
To establish credibility, modeling outputs must demonstrate robustness and undergo rigorous validation studies to ensure their accuracy, which is an ongoing process Moreover, outputs will be more valuable if they can specifically identify critical conditions that may lead to biological contamination or physical deterioration, rather than just predicting physical parameters Presenting results in probabilistic terms, such as "most likely" values with ranges or associated uncertainties, will provide users with deeper insights and more reliable information, compared to absolute, deterministic outputs.
• Translate Modeling Results into Practice Current models tend to be complex, difficult to use and hard to interpret, or so simplified that their results may be unreliable Experts can make good use of state-of-the-art models, but typical building designers face a much greater barrier In the near term, models can and should be used by the experts to do comparative
Building moisture and durability studies can significantly reduce the need for field testing by providing valuable insights into building assemblies By leveraging these results, design guidance can be created and disseminated to practitioners, ultimately informing their decision-making processes To achieve long-term benefits, models should be applied to analyze individual building designs, with the most effective approach involving tight integration with widely-used design tools This integration enables users to access modeling results without requiring specialized knowledge or re-entering building information, streamlining the design process and enhancing overall building performance.
Summary of Suggested Moisture Research Projects
Here is a rewritten paragraph that captures the meaning of the original text while complying with SEO rules:"A comprehensive list of research projects categorized under key headings is provided on the following page, along with their designated priority levels as determined by the Expert Panel The projects are classified as either very high priority or high priority based on the panel's expert input, ensuring a clear roadmap for future research endeavors."
Summary List of Moisture Research Projects
Goal or Project Title Priority
Build Additional Knowledge about the Moisture Problem in Housing (Section 3)
Compile statistically valid data on the relative frequencies and severity of different types of moisture problems, in both new and existing homes Very high
Perform an in-depth analysis of existing AHS data on moisture problems Very high Quantify the physical damage resulting from different types of moisture problems
Characterize the moisture performance of existing homes through a field testing protocol Very high Investigate the evolution of legal and insurance claims relating to mold and moisture problems
Improve understanding of the health effects of indoor moisture problems, especially mold
Update recommendations of appropriate target indoor humidity levels to reflect health and other effects
Prevent and Correct Specific Moisture Problems (Section 4)
Gather, disseminate and transfer residential flashing know-how to user audiences High Determine optimum foundation drainage practices
Develop guidelines for building material moisture content prior to building enclosure
Assess the drying performance of typical wall systems in U.S climates and disseminate the results Very high Develop educational tools to enable and certification programs to recognize good moisture control practices
Very high Review current building code flashing and overhang requirements, and develop code changes to fill gaps
Develop gutter scoping requirements and design criteria for pitched roofs
Clarify requirements for crawl space ventilation and moisture protection design details
Develop inexpensive, unobtrusive moisture sensors and data collection devices
Promote the development of technology for passive detection of moisture problems
Create and publish a model building envelope maintenance and repair guide for owners and property managers
Introduce improved structural and finish materials that are resistant to moisture and decay
Validate the performance benefits of a "smart" vapor retarder, and work to promote appropriate use of High improved vapor retarder technologies
Determine feasibility and cost of residential air-conditioning systems capable of meeting latent loads under part-load conditions
Work to ensure that expanded use of mechanical ventilation systems helps reduce rather than worsens moisture problems
Develop a mold resistance rating and associated moisture performance test procedures for air handling High equipment
Realize the Potential of Moisture Modeling Tools (Section 5)
Compile specialized weather data sets
Develop statistically validated procedures to assess internal moisture loads for use in hygrothermal analyses and related engineering studies Very high
Develop a generalized approach to determine cladding pressure differential for purpose of cladding structural and rain-penetration design
Development and maintenance of material properties by industry for use by designers
Generate information on the "aged" properties of common building and insulating materials
Strengthen validation studies and incorporate consensus standards for accuracy
Establish "threshold" values for temperature, relative humidity and duration to initiate biological, chemical and mechanical damage of building materials and components
Develop a generalized approach to determine cladding pressure differential for purpose of cladding structural and rain-penetration design
Develop stochastic moisture models using probabilistic outputs (ranges) to reflect errors due to weather High (external loads), material variations, and internal load variations
Use models to develop design guidance and disseminate the results
Use models to identify optimum properties of specific building materials
Integrate models tightly with standard design tools
Build Knowledge about Moisture Problems
Develop Reliable Quantitative Information Documenting the Nature, Frequency, Severity and Impacts of Moisture Problems in Housing
Current data on moisture problems in housing is largely theoretical or based on isolated field studies, with little attention given to their relative frequencies and severity in both new and existing homes Existing statistical studies are limited in scope and vary in their definition of a "moisture problem," making it difficult to make informed decisions about mitigation steps To address this knowledge gap, compiling statistically valid data on the prevalence and severity of different types of moisture problems is crucial, enabling more effective decision-making and prioritization of cost-effective solutions.
The American Housing Survey (AHS), sponsored by HUD and conducted every two years, provides valuable insights into the prevalence of leaks in US housing units With a random sample of over 60,000 units, the AHS collects data on roof, wall, basement, water heater, and pipe leaks, offering a comprehensive understanding of the issue Notably, the 2001 AHS revealed that approximately 12% of occupied housing stock experienced leaks in the roof, basement, walls, or other exterior components within the last 12 months, with a higher incidence in newer homes.
7 percent However, the current AHS does not attempt to determine the severity of these problems, nor does it touch upon any of the variety of water vapor-related problems The AHS could readily be revised to expand the scope of moisture problems covered, add additional questions about phenomena such as condensation leading to puddling of water and cooling season humidity control, and to inquire as to the severity of other leaks reported by
Building moisture and durability are crucial factors in ensuring the comfort and well-being of occupants Ideally, data collected through surveys such as the American Housing Survey (AHS) can help determine whether issues arise from design flaws, workmanship errors, or product failures The AHS is a valuable tool in this regard, offering a comprehensive and easily accessible means of gathering information, surpassing other survey methods in terms of convenience and effectiveness.
Cost: Low Modification of the AHS to expand coverage of moisture problems would be relatively inexpensive since the survey is already in place.
The implementation timeline for survey modifications is relatively short to medium, with development potentially completed in under a year However, due to inherent time lags, the actual rollout of a modified survey and subsequent analysis of the results may span several years.
Priority: This project was identified as very high priority by the Expert Panel.
An in-depth analysis of existing American Housing Survey (AHS) data on moisture problems can provide valuable insights into the issue By utilizing complete data sets from the AHS, researchers can create a comprehensive statistical picture of moisture-related problems, going beyond the information presented in published tables This analysis can explore two key themes: identifying housing characteristics and occupant data associated with reported leaks from external and internal sources, and investigating whether moisture problems occur randomly or recur in specific homes over time By examining these themes, researchers can develop a multivariate predictive model of conditions associated with moisture problems, ultimately informing effective strategies for addressing the issue.
Priority: This project was identified as very high priority by the Expert Panel.
• Quantify the physical damage resulting from different types of moisture problems
Here is a rewritten paragraph that captures the essence of the original text, optimized for SEO:"Understanding the incidence of leaks and moisture accumulation is only the first step; the next crucial aspect to investigate is the extent of damage to buildings and their contents This includes assessing the frequency of structural damage, such as roof or wall sheathing deterioration, as well as secondary issues like insect infestation, visible mold and mildew, and damage to interior finishes requiring costly repairs or replacements Moreover, the impact on personal property stored in homes must also be considered These physical outcomes necessitate significant time and financial investments to rectify, making reliable estimates of the economic costs associated with unwanted moisture essential to fully grasp the scope of this problem Developing these estimates will require more complex methods and a longer timeframe, but will ultimately provide a comprehensive understanding of the issue."
• Characterize the moisture performance of existing homes through a field testing protocol
This project aims to intensively collect data on moisture-related issues in newly-built homes across the country, focusing on a smaller sample of several hundred homes up to 5 years old The study will involve field measurements, data monitoring for up to a year, and survey questions for occupants to gather information on construction types, mechanical systems, and indoor conditions The primary goals are to identify concealed moisture problems, characterize indoor and outdoor conditions, and analyze internally generated moisture loads The collected data will be used to study and predict internal conditions using modeling tools, taking into account location, construction, and external factors The project will involve developing a comprehensive inspection and monitoring protocol, survey design, field execution, and data analysis to achieve these objectives.
Priority: This project was identified as very high priority by the Expert Panel.
The rise in lawsuits related to mold and moisture problems has led to significant changes in policy language among property insurers and builders' risk insurers, as well as modifications to warranty terms by manufacturers, retailers, and home builders High-profile jury awards and product recalls, including those for EIFS, hardboard siding, and OSB siding, have contributed to this trend, which has also been driven by changes in state warranty laws extending coverage for new homes A comprehensive analysis of litigation, warranty claims, and insurance claims data is necessary to identify and document trends in this area, providing valuable insights for businesses throughout the supply chain By examining these trends, it is possible to determine whether the underlying moisture problem is increasing or if changes in the legal and insurance landscape are driving the growth in claims.
Improve Scientific Understanding of the Relationship Between Moisture in
• Improve understanding of the health effects of indoor moisture problems, especially mold
Exposure to moisture and its by-products, such as mold, in residential environments poses significant health concerns, with reported effects ranging from allergic reactions and sinusitis to severe respiratory issues, including asthmatic attacks and even acute pulmonary hemorrhage.
BUILDING MOISTURE AND DURABILITY the lungs) in infants (although the study reporting this latter effect was subsequently withdrawn) While this has surely increased interest in management of indoor moisture (which may offer other benefits as well), it has also created unnecessary fear about common phenomena such as small spots of mold or mildew in shower compartments One result has been to leave some occupants afraid to take common-sense cleanup actions
The latest study on the subject, Damp Indoor Spaces and Health, was commissioned by the Centers for Disease Control, developed by a committee operating under the National Academy of Sciences, and published in early 2004 While that report concluded that a variety of health outcomes were associated with exposure to damp indoor environments, including upper respiratory tract symptoms, cough, wheeze, and asthma attacks in asthmatics, it also found that there was insufficient information to assign a causal relationship between dampness and any of those outcomes It concluded that excessive indoor dampness was a public health problem, although the word "excessive" appears key to this conclusion Finally, the report also acknowledged that as yet there was no basis for recommending appropriate levels of dampness reduction or "safe" levels of exposure to dampness-related agents Numerous recommendations for further research appear in the study Some are covered elsewhere in this report (e.g reviewing HVAC systems as a potential site for growth and dispersal of microbial contaminants, or development of designs, construction and maintenance practices for buildings that reduce moisture problems, and development of building materials that resist microbial contamination when wet), but many others are not
To further understand the health implications of indoor dampness, research should focus on identifying causal relationships between dampness and health outcomes, such as asthma and sinusitis, and assessing the contribution of residential dampness to the overall disease burden While the building science community plays a supporting role in this research, it's essential to prioritize preventing moisture problems, as their impacts extend beyond health effects.
Cost: High Broad epidemiological studies are difficult and expensive.
Maintaining optimal indoor humidity levels is crucial for occupant comfort, health, and material durability The recommended indoor relative humidity range of 30% to 60% in ASHRAE Standard 55 may need to be revised to reflect the latest health considerations and material durability Lower humidity levels, such as 15% in very cold climates, may be necessary to prevent microbial growth and minimize allergens, but extremely low relative humidity can also cause unpleasant effects Moreover, humidity variations within a conditioned space can lead to mold growth on cold exterior walls in winter, and seasonal swings in humidity can cause stresses in building assemblies, resulting in cracks and splits.
Maintaining optimal building moisture and durability is crucial, yet it's a complex issue due to varying conditions within building microclimates that can lead to undesirable localized effects To address this challenge, a comprehensive re-evaluation of target indoor humidity levels is necessary, taking into account factors such as occupancy type, occupant characteristics, climate, and more By reconciling these variables and producing consensus recommendations, designers and building operators can access a valuable resource that helps inform their decisions and ensure a healthier, more sustainable indoor environment.
Responsibility: Public-private, including involvement of the design and public health communities.
Prevent and Correct Specific Moisture Problems
Encourage Moisture Protection in Building Design and Construction
• Gather, disseminate and transfer residential flashing know-how to user audiences
Flashings are an essential component of building envelopes, especially roofs and walls They come in many different varieties, each tailored for specific conditions, and they may be installed by several different subcontractors on a single house Improperly formed or installed flashing can lead to significant bulk water leakage, and can be costly to repair once the home is completed Improving the quality and workmanship of flashing would be a major step towards reducing leaks through building envelopes Flashing practices are described in many different sources; some in the public domain and many others under the control of different industry associations The first part of this project would involve inventorying existing flashing resources, identifying the most useful ones and working with the sources to compile a concise, accurate guide to flashing aimed at audiences who actually select and install them in housing Coverage would include roof penetrations, valleys, chimney flashing, drip edges, step-flashing, counterflashing, and flashing of window and doors Such a guide would be quite valuable even if it did not cover every possible combination of roofing and siding systems The second part of the project involves outreach designed to transfer this knowledge to workers responsible for flashing installation This represents a major challenge given the dynamic nature of the workforce and the multiple trades involved It will require a sustained effort through multiple avenues including trade associations and building firms
Responsibility: Public sector, in collaboration with major product and material interests Cost: Low to develop materials; medium to high to perform outreach
Time: Short to develop materials, then ongoing
Priority: This project was designated high priority by the Expert Panel
Effective foundation drainage is crucial in preventing moisture intrusion and ensuring the structural integrity of a building To achieve this, it is essential to divert rainwater and roof drainage away from the building perimeter through proper site development, rough grading, backfilling, compaction, and finish grading Optimum foundation drainage practices involve considering various factors, including gutter overflow, backfill compaction, and site grading, particularly in areas with closely spaced houses or sloping parcels Research has shown that minimum building code requirements for slope away from the foundation may not always be sufficient, and settlement can alter drainage patterns over time Therefore, developing recommended practices for optimum backfilling, site grading, and rainwater discharge through downspouts is vital, taking into account the specific needs of wet and dry climates to minimize moisture intrusion and soil moisture levels at the foundation.
Responsibility: Shared between the public sector, the building industry and material interests for concrete and masonry.
• Develop guidelines for building material moisture content prior to building enclosure
Building materials like framing lumber and wood panels often contain moisture that can dry out over time, while others like fresh concrete and wet-spray cellulose are naturally or intentionally wet However, if these materials remain damp for extended periods, they can become susceptible to mold growth, especially in regions with high humidity and rainfall, such as the Pacific Northwest To mitigate this issue, guidelines are needed to determine the optimal moisture levels for moisture-sensitive building materials before they are enclosed or integrated into unventilated assemblies, providing a crucial benchmark for builders and contractors to ensure safe and durable construction.
Responsibility: Public sector and material interests.
Evaluating the drying performance of typical U.S wall systems is crucial, as occasional bulk water leakage into walls can occur despite their inherent drying ability The drying performance of a wall is influenced by various climate and construction variables, making it essential to consider current construction materials, realistic indoor and outdoor moisture levels, air movement, vapor diffusion, and moisture storage and release in testing and modeling Comparative rating of wall systems in terms of drying potential and climate would provide valuable insights for building designers, and reliable ratings can be developed through extended testing and benchmarking of various siding types, including fiber-cement and wood products By completing this process, researchers can determine comparative performance and extend results to other climates, with periodic revisions necessary to reflect evolving modeling tools and data sets.
Responsibility: Public sector, although broad-based material interests would probably collaborate.
Cost: Medium to high, depending on scope and required field work.
Time: Medium to long-term.
Priority: This project was identified as very high priority by the Expert Panel.
To promote good moisture control practices, it's essential to develop educational tools and certification programs that cater to the construction workforce Creating educational programs can raise awareness and communicate key information about best building practices, while certification programs can document successful completion of a basic education program By packaging and delivering this information effectively, certification can serve as a motivating force and a marketable credential in a competitive environment Key tasks include identifying key topics, compiling content, developing a delivery vehicle, defining certification criteria, and establishing a certification mechanism, all of which should be carried out in conjunction with private sector associations and potentially sponsored by manufacturers.
Priority: This project was identified as very high priority by the Expert Panel.
Improve Moisture Protection Through Codes and Standards
Here is a rewritten paragraph that captures the essence of the original text while complying with SEO rules:"Building codes have shifted towards performance-oriented standards, inadvertently omitting crucial details on traditional building envelope design that prevent moisture issues This gap in information has raised concerns about the effectiveness of current building codes in ensuring optimal building performance In contrast, documents like the 1958 FHA Minimum Property Standards and Wood Frame House Construction (USDA Handbook No 73) offer a more comprehensive approach to envelope flashing and roof overhang design To address this issue, it is essential to review and revise current building codes to incorporate improved concept details for envelope flashing and simplified design recommendations for roof overhangs, while still allowing for innovation and evolution in building practices."
Time: Short time to develop changes; uncertain time to incorporate changes into codes
Developing gutter scoping requirements and design criteria for pitched roofs is crucial in preventing foundation moisture problems In many parts of the country, working gutters and downspouts serve as a vital line of defense against water damage Without properly functioning gutters, homeowners may face issues ranging from wet basements to severe foundation wall failure Regular maintenance is key to preventing clogged downspouts and gutters, which can exacerbate these problems if left unaddressed.
Building moisture and durability issues can arise from inadequate gutter systems, yet the International Residential Code lacks specific requirements for installing gutters on pitched roofs and downspout placement and sizing To address this gap, a comprehensive project would establish criteria for determining when gutters are necessary, provide guidance on proper attachment and detailing at the roof edge, and develop a methodology for optimal downspout placement and sizing Additionally, the project would investigate effective drainage solutions at ground level and compile information on various methods for protecting gutters from debris accumulation, drawing from relevant state and local building codes and industry publications.
Responsibility: Public sector, together with producers of gutter guard systems.
• Clarify requirements for crawl space ventilation and moisture protection design details
The debate on how to build dry crawl spaces has been ongoing for decades, with a focus on the necessity of crawl space ventilation However, other factors such as poor site drainage, water vapor release from the ground, and marginal hydrologic conditions can also contribute to moisture problems Traditional code requirements for fixed ventilation openings have been questioned, citing successful experiences with unvented crawl spaces in certain climates Despite this, there is limited long-term US experience with unventilated crawl space construction, making it difficult to predict which crawl spaces will perform satisfactorily and which will not, highlighting the need for a more comprehensive approach to building dry crawl spaces.
International Residential Code approved in 2004 are intended to simplify the use of unventilated crawl spaces, yet the requirements are exacting and performance-oriented which will not facilitate their use There remains a continuing need for testing, monitoring and demonstration of crawl spaces with and without ventilation, positive drainage and other moisture protection strategies to identify the essential site, design, and construction details for acceptable performance There is also a potentially important role for modeling in extending this research, given the high cost and long time required for field demonstrations, assuming that models can be shown to accurately predict failures that occur in practice
Detect and Correct Moisture Problems Before Serious Damage Occurs
Developing affordable and unobtrusive moisture sensors and data collection devices is crucial for detecting hidden moisture issues in concealed spaces, such as wall cavities and water pipes, which can lead to costly problems like mold growth, wood decay, and insulation saturation if left undetected Early detection and repair of these issues can significantly reduce the economic burden of moisture-related damage, making it essential to invest in innovative, non-destructive methods for monitoring moisture intrusion and internal condensation.
Building moisture and durability can be effectively monitored using innovative tools such as broadband radar, which can detect moisture and mold in building assemblies However, these tools are often expensive and require specialized expertise, limiting their accessibility Fortunately, advancements in electronic component miniaturization have enabled the development of small, affordable devices that can measure temperature and relative humidity, logging data over extended periods Strategically placing these devices in areas prone to moisture, such as beneath windows, plumbing connections, crawl spaces, or attics, allows for real-time monitoring and quick data analysis, enabling early detection of moisture intrusion and elevated humidity.
• Promote the development of technology for passive detection of moisture problems As an extension to the previous item, it seems clear that the ideal method of monitoring and detecting moisture problems (especially in concealed spaces) would be completely passive, requiring no intervention by the user but providing a warning when conditions warrant One example is an air conditioner condensate pump with an overflow switch that shuts off the compressor before allowing condensate spillage In terms of detection, for less than $20 a consumer can already buy a battery-powered thermometer with a wireless remote temperature sensor that has a 100-foot range Up to three temperature sensors can be used with a single base station, and relative humidity sensing could easily be added It might also be possible to use active RFID tags (chips with antennas and an embedded power source) to send distress signals when crawl spaces or wall cavities become excessively damp There is ample room for other approaches The key is for the user to be notified of hostile conditions automatically, rather than relying on destructive inspections or diagnostic equipment used by experts
Responsibility: Public-private The private sector has a role because this could lead to marketable products.
• Create and publish a model building envelope maintenance and repair guide for owners and property managers It is not realistic to think that improved design and construction practices will eliminate all moisture problems, especially as buildings age Responsibility for preventing and correcting problems ultimately falls on the owner or property manager, who may not fully appreciate the issues or understand the best approach to any particular situation A building envelope maintenance and repair guide directed at this audience should include (1) a schedule of generic inspection procedures with recommended frequencies, (2) information about how to correct problems identified during the inspection or when to bring in a specialist, and (3) a troubleshooting guide for identifying the cause of known or suspected water intrusion problems As a supplement or alternative to a printed guide it would also reasonably straightforward to develop and deploy a "moisture problem troubleshooter" over the internet Such a tool would allow users to identify a problem, then probe them with questions to narrow down potential causes, and finally present information
Effective building moisture and durability management requires a comprehensive approach to remediation, considering multiple causes and consequences of moisture-related issues A non-linear, web-based tool utilizing hyperlinks can provide a more tailored and user-friendly experience, allowing individuals to navigate complex information and identify specific solutions to their unique problems This approach acknowledges that a single problem can stem from various causes, and a single cause can lead to multiple problems, thereby reducing repetition and increasing the tool's overall efficiency.
Responsibility: Public-private Numerous product, material, financial and insurance interests have a stake in this activity.
Use New Technologies to Reduce Vulnerability to Moisture Damage
The development of improved structural and finish materials has been crucial in addressing moisture-related issues in building construction Over time, innovative products such as vinyl siding, cement-based panels, treated lumber, and membrane roof underlayments have emerged, offering enhanced resistance to moisture and decay Further research is needed to evaluate the performance of new materials, including their resilience to on-site moisture, and to develop systems for treating framing and truss lumber to prevent mold growth Additionally, assessments of alternative products should consider factors such as moisture, structural, fire, thermal performance, toxicity, cost, installation, and integration with other building materials, with a focus on improving the overall performance and reducing maintenance requirements of materials like gypsum board and paints.
Cost: Moderate for incremental improvements; high for major product changes.
The "smart" vapor retarder, such as MemBrain, offers performance benefits by adapting to changing environmental conditions, with low permeance in dry conditions and higher permeance in damp conditions This innovative technology, commercially available in the US, functions like a conventional vapor retarder in cold weather, blocking vapor diffusion into the wall cavity, but allows damp wall cavities to dry towards the indoors in hot weather Suitable for mixed-humid climates, its benefits warrant real-world study to validate its effectiveness, while other approaches, including one-way vapor transmission, and optimal vapor retarder properties, also require investigation for potential commercialization and improved building performance.
BUILDING MOISTURE AND DURABILITY sides of a wall in any climate and positioned to allow drying from the inside in either direction This would resolve many problems that arise today
Priority: This project was designated high priority by the Expert Panel.
• Determine feasibility and cost of residential air-conditioning systems capable of meeting latent loads under part-load conditions The oversizing of air conditioners is widely cited as a contributor to moisture problems in hot weather, since an oversized system will meet sensible loads and cycle off before extracting sufficient moisture from the air The result is a cool house with high humidity But even a "properly" sized system can experience similar problems when operating below design outdoor temperature; in effect under those conditions it performs like an oversized system As a result, removing humidity on days when temperatures are only slightly elevated can require cooling the house to an uncomfortable degree, even with a properly sized system Reheating the output air can be done, but only at a high energy penalty Campaigns to discourage equipment oversizing have been attempted with limited success since there are evidently institutional reasons for oversizing equipment
In many parts of the US, incorporating mechanical ventilation may inadvertently exacerbate latent loads, highlighting the need for innovative engineering solutions to address this issue A viable approach could involve integrating supplemental dehumidification systems with air conditioning operations to provide comprehensive load management Ideally, the technology should offer seamless dehumidification and cooling across various load conditions, not just at design specifications As an interim solution, a stand-alone dehumidifier with combined controls can be employed, allowing the air conditioner to manage sensible loads while the dehumidifier tackles latent loads when sensible loads are minimal or non-existent.
Responsibility: Private sector HVAC firms.
The expanded use of mechanical ventilation systems is crucial in reducing moisture problems, rather than exacerbating them, to improve indoor air quality and create healthier homes As builders increasingly market "healthy" features and codes evolve, the adoption of mechanical ventilation systems is likely to grow However, while these systems can dilute indoor moisture levels under certain conditions, they can also create or worsen moisture problems if not designed or installed correctly To address this issue, research is needed to develop simple, pre-wired systems that do not require complex connections in the field, and design tools that integrate with HVAC load calculations to ensure reliable performance and minimize moisture-related issues.
Effective building moisture management and durability require a well-designed ventilation system, as it can significantly impact load performance Implementing performance monitoring systems is crucial to ensure proper ventilation, thereby maintaining optimal moisture levels and preventing unnecessary humidification Furthermore, understanding the feasibility of retrofitting mechanical ventilation systems into existing homes can help address existing moisture issues, ultimately enhancing building durability and indoor air quality.
Responsibility: Public-private Many public agencies advocate use of these systems, and private entities benefit from their use.
Here is a rewritten paragraph that captures the essential meaning and complies with SEO rules:"Air handling equipment in forced-air HVAC systems poses a significant concern in building science, particularly in humid climates, due to the accumulation of moisture in concealed spaces The air handler environment is prone to dampness, darkness, and condensate buildup during the cooling season, which can lead to increased humidity in the output air stream and the growth of biological contaminants Unlike energy performance, which is measured by standardized efficiency ratings, there is currently no straightforward way for consumers to evaluate a unit's moisture collection and disposal capabilities Developing a mold resistance rating and associated moisture performance test procedures for air handling equipment is essential to address this issue and provide consumers with a reliable way to assess the performance of different units."
The vulnerability of an air handler to internal moisture problems is influenced by a range of variables, including fin spacing on the A-coil, fan design, condensate drainage efficiency, air filtration effectiveness, and the presence of time delay relays These factors often involve trade-offs between equipment efficiency and moisture performance, making it challenging to develop test methods that accurately assess moisture performance To address this, researchers are working to create a single, easily communicable index (e.g., a 0-20 scale) that combines multiple indices of moisture control Additionally, efforts are being made to design equipment that can better handle moisture and incorporate technologies that prevent biological contamination, such as UV irradiation or anti-microbial surface linings.
1 Suggested by Dr Subrato Chandra
Responsibility: Public sector, in collaboration with HVAC equipment manufacturers and associations.
Time: Medium to develop, long to implement.
Priority: This project was designated high priority by the Expert Panel.
Realize the Potential of Moisture Modeling Tools
Fill in Data Gaps that Limit Modeling Accuracy
The physics that underlie moisture modeling are relatively well understood, but the output of a model is only as accurate as the input data At present there are several types of input data that are poorly defined, which creates ambiguity or uncertainty in interpreting modeling outputs
To accurately model key weather phenomena, such as wind-driven rain in the U.S., it is crucial to compile specialized weather data sets that fill existing gaps High-resolution data on coincident wind speed, wind direction, and rate of precipitation are necessary for precise modeling However, current data, even when collected hourly, often averages out extreme events that significantly contribute to water intrusion, which can overshadow moisture contributions from humid air or vapor diffusion, making accurate data collection a pressing concern.
Responsibility: Private sector (ASHRAE), with public sector support
Cost: Low to medium, depending on scope, resolution and number of locations
Time: Medium for initial development; further refinement will be needed over the long-term
To accurately model the moisture balance of buildings, statistically validated procedures must be developed to assess internal moisture loads, a crucial component of hygrothermal analyses and related engineering studies Documenting internal moisture load profiles for U.S houses is essential, as it requires quantifying the moisture released by normal occupant and household activities However, a significant gap in field data exists, and current modeling suggests that the difference between best-case and worst-case scenarios can have drastic consequences on a building's functionality To address this, field measurements of moisture generation and levels are necessary to provide improved data, which should ultimately be incorporated into consensus standards to ensure consistent application throughout the modeling and design communities, specifying internal loads, treatment of combined loads, and the use of "worst-case" or "best-case" loads.
Implementing standardized "average" loads or variations thereof can significantly enhance modeling accuracy, while also laying the groundwork for the emerging field of "moisture engineering" by establishing a solid foundation for this science.
Cost: Medium to develop data
Time: Medium for data gathering, long for standards development
Priority: This project was identified as very high priority by the Expert Panel
• Development and maintenance of material properties by industry for use by designers 2
While existing data from reputable sources such as ORNL, Canadian, and ASTM provides some insights, there is a lack of consensus on standardized properties and limited laboratory capacity for relevant testing Key parameters, including moisture absorption and release curves in relation to ambient humidity, are not widely utilized The development of a comprehensive database through centralized testing is a labor-intensive, time-consuming, and costly process A more efficient approach would be a system where manufacturers or trade groups take responsibility for measuring and reporting their own material properties.
2 Suggested by Andre Desjarlais and Dr Achilles Karagiozis
Building manufacturers can enhance the durability of their materials by disseminating crucial information about moisture-related performance properties, which can be utilized by moisture-modeling software in the design process, similar to how structural performance properties and thermal performance values are obtained from manufacturers to inform design decisions.
Time: Short to medium, depending on capacity of qualified test laboratories.
Current building models often rely on idealized assemblies based on the performance properties of new materials, neglecting the impact of aging and environmental cycles on their degradation over time As a result, these models struggle to accurately predict how performance changes after years of exposure to heat, cold, damp, and dry conditions While new systems typically perform well, their performance can deteriorate significantly after five, ten, or twenty years, with deterioration often accelerating rapidly once it begins.
Cost: Medium to high, depending on number of materials and variations.
Demonstrate Robustness and Extend Modeling Capabilities
• Strengthen validation studies and incorporate consensus standards for accuracy
Numerous simulation tools have been developed Most have been abandoned or are no longer supported; they served a research need at a point in time, but have no lasting value
Most available tools, despite being touted as "easy to use", have a steep learning curve and are often unusable by non-developers Current validation methods typically involve lab tests under ideal conditions, which may not translate to accurate results in real-world applications Moreover, the lack of recognized standards for validation makes it challenging to interpret results and determine what level of accuracy is acceptable To build trust in modeling outputs, users need robust evidence that the results are meaningful, a task that requires ongoing effort as models are continually revised and updated.
Responsibility: Public sector Model developers typically perform these studies.
• Establish "threshold" values for temperature, relative humidity and duration to initiate biological, chemical and mechanical damage of building materials and components 4
While experience has shown that buildings can easily survive brief excursions into temperature and moisture regimes that would be destructive if sustained over prolonged
3 Suggested by Dr Kumar Kumaran
4 Suggested by Dr Kumar Kumaran
Establishing clear criteria for building moisture and durability is crucial, yet currently, there are no universally accepted standards to define excessive moisture levels and durations To address this, input from microbiologists and material scientists can be used to develop criteria that filter modeling outputs, identifying combinations of conditions that may lead to destructive outcomes By using multiple criteria, this approach is more accurate than relying on single-variable rules of thumb, such as condensation occurrence or peak relative humidity exceeding 70 percent These criteria can also inform a broader framework for moisture engineering in design, paralleling structural engineering approaches, and serve as a valuable resource for manufacturers developing high-performance products.
Responsibility: Public sector with input from product manufacturers.
Cost: Low to medium, depending on scope and testing required.
Time: Short for basic criteria.
Here is a rewritten paragraph that captures the essential meaning of the original text, optimized for SEO:Developing a generalized approach to determine cladding pressure differential is crucial for both structural and rain-penetration design The pressure difference across cladding is a critical factor in wind load resistance and a key parameter in modeling rainwater infiltration into wall assemblies Research suggests that pressure-driven rainwater entry can surpass air flow and vapor diffusion as a primary moisture source To address this, a computerized method like the 'RAIN' model by NRC-IRC can be employed However, standardized test methods are necessary to quantify the relationship between pressure differences, wind speed, direction, and other parameters Benchmarking modeling of pressure differentials across claddings requires testing and monitoring a range of assemblies, which can be done cost-effectively using existing demonstration buildings or laboratory testing with a well-developed test protocol informed by field data.
Responsibility: Private-public Trade associations and manufacturers should lead these efforts, which are relevant to structural design as well as moisture penetration.
Traditional moisture models have limitations as they are deterministic, failing to account for uncertainties stemming from material variations, workmanship, external loads, and internal loads In contrast, stochastic moisture models utilize probabilistic outputs, providing users with a range of possible outcomes and reflecting the inherent uncertainty in modeling results By explicitly modeling key inputs as random variables, these models can generate results as ranges or bands, offering a more comprehensive understanding of the potential variability in moisture levels This approach enables users to better assess and manage the risks associated with moisture-related issues, ultimately leading to more informed decision-making.
5 Suggested by Dr Achilles Karagiozis
BUILDING MOISTURE AND DURABILITY point estimates This would highlight some of the uncertainty inherent in attempting to analyze moisture, and help users distinguish meaningful differences from small, unimportant differences The research challenges are to identify and characterize the major sources of uncertainty in the modeling, and coping with the computational demands of monte carlo approaches that would likely be required to determine how the uncertainties propagate into modeling results
Responsibility: Public, as with model development in general.
Priority: This project was designated high priority by the Expert Panel.
Translate Modeling Results into Practice
To overcome the limitations of current models in developing design guidance, experts can utilize state-of-the-art models to conduct comparative studies of building assemblies, reducing the need for field testing By calibrating these models with baseline field results, they can efficiently extend the findings to various geographic locations, climates, and construction variations This approach enables the creation of simplified guidance for practitioners, providing valuable insights into the performance of different building assemblies and their resistance to moisture accumulation, ultimately informing evidence-based design decisions.
Responsibility: Public sector, possibly in cooperation with affected product interests.
Cost: Medium for modeling; higher if field testing is also required.
Time: Medium for modeling; longer if field testing is also required.
Researchers can utilize moisture modeling tools to identify the optimum properties of specific building materials, enabling them to better understand how different structures respond to moisture loads By iterating through various possible properties of a given layer, such as a vapor retarder, these models can determine the ideal combination of properties that demonstrates the best resistance to moisture This approach can be particularly useful when the ideal properties remain stable despite small changes in other components and modeling inputs, allowing material scientists to modify their products to more closely approximate the ideal properties.
Responsibility: Public sector, since intimate knowledge of the models is required.
To improve the design of specific buildings, modeling tools must be tightly integrated with standard design (CAD) software tools This integration enables moisture analysis software to analyze building design files and present results to designers without requiring additional steps or input data The software should also provide suggestions for design improvements to enhance moisture tolerance Achieving seamless integration has been a challenge, with most CAD programs not using 3-D objects and some employing proprietary file formats, hindering progress in this area Effective integration would allow for background analysis and suggestions for design improvements, ultimately enhancing the design process.
Responsibility: Public sector, ultimately becoming a shared public-private activity.
Cost: Medium to demonstrate the concept.
Time: Medium to demonstrate the concept.
APPENDIX A LITERATURE REVIEW AND ANALYSIS
APPENDIX A: LITERATURE REVIEW AND ANALYSIS