Retrospective field study of the long-term performance of remediation methods in major building crawl space foundations

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1 Indoor Air 2008, August 2008, Copenhagen, Denmark - Paper ID: 124 Retrospective field study of the long-term performance of remediation methods in major building crawl space foundations Sarah Figley 1,*, Donald Figley 1 and Don Fugler 2 1 Figley Consulting Associates Ltd., Saskatoon, SK., CAN 2 Canada Mortgage and Housing Corporation, Ottawa, ON., CAN * Corresponding figley.consulting@sasktel.net SUMMARY This paper summarizes a major field study that was conducted to assess the long-term performance of crawl space foundation remediation strategies. The eight crawl spaces in institutional buildings in Saskatchewan, Canada had been remediated over the past seven years. Basic building science and indoor air quality design concepts were initially applied to assess the water damaged, deteriorated and contaminated crawl spaces. Remediation methods were developed and implemented to address performance deficiencies and return the crawl spaces to an acceptable and durable condition. The remediated crawl spaces have been regularly monitored and all of them continue to provide excellent performance. KEYWORDS Crawl spaces, Remediation strategies, Building performance, Indoor air quality INTRODUCTION The research study was conducted as a retrospective investigation of the long-term durability and effectiveness of crawl space remediation strategies that have been used in projects during the past seven years 1. Background information pertaining to basic issues related to the performance of building crawl spaces has been previously discussed by Figley (2002). Crawl spaces are shallow foundations used to support a variety of buildings. At a preliminary stage, the foundations must be designated as either, 1) unheated or unconditioned meaning the crawl space provides only structural support and is environmentally decoupled from the building indoor environment or 2) heated or conditioned meaning the crawl space is a fully integrated component of the building indoor environment (ASHRAE, 2005; National Building Code of Canada, 2005). Although it should be obvious that spaces within the conditioned envelope of buildings should be maintained in a similar manner to other occupied spaces, for some unknown reason, this basic concept seems to be lost along the life cycle of thousands of major buildings encompassing millions of square metres of space. Often, poor design and/or poor construction have set up conditions that assure the failure of these critical components. All of the crawl spaces included in this study were originally designed as heated/conditioned crawl spaces and were considered as conditioned spaces completely within the building interior. Due to basic deficiencies or weaknesses in the design and/or construction, or problems with the on-going maintenance, all of the crawl spaces had become deteriorated, contaminated areas that could potentially have a significant negative impacts on the indoor environment and physical performance of the building. Extensive mold contamination of the

2 building structure and surrounding debris, spilled sewage, and dead rodents were common sources of crawl space contamination. Through a combination of design and use issues, these essential components of the building assembly had become deteriorated. As these issues were out of sight, out of mind, their fundamental purpose and relationship to the building as a whole, as well as their performance requirements, had been neglected by the facility owners and operators. Many of the crawl spaces included in this study shared some common initial problems/issues related to moisture management, however many of the crawl spaces presented with one or more unique issue(s), which required different remediation strategies to be implemented. Some remediation methods had not been used in previous conventional clean-up projects, but were novel engineering suggestions employed to experiment with product durability, cost, mold removal techniques or improve past techniques. Regardless of the clean-up and repair techniques that were used in each of the test-case crawl spaces, the final design objectives for all of the crawlspaces were the same, to: 1) control moisture, 2) provide a continuous and durable floor surface and environmental separation, 3) clean the space to return it to normal building environment conditions, 4) isolate the crawl space from the occupied areas of the building by continuously depressurizing the crawl space with a dedicated exhaust system, 5) control access to the area, and 6) make the area easily accessible for inspection and maintenance. In order to assess the long-term performance of the remediation projects, each crawl space remediation project included in this research study was required to have been completed for a minimum of two-years (range 2-7 years). The remediation strategies and final outcomes of each case study have allowed conclusions and recommendations to be made based on successful remediation techniques. METHODS Field records from more than thirty completed major building crawl space remediation projects were reviewed to identify an age stratified sample of eight crawl space remediation projects that provided a cross-section of information on various crawl space configurations and issues. The background file for each selected project was examined in detail and information related to the initial underlying problems and remediation plan was summarized. A detailed followup field inspection was conducted to assess the current condition of the building. This information was used to prepare the individual project case study report and overall summary. Crawl space performance issues For each project, an initial information review was completed to identify the root causes of the original crawl space performance problems. Many of the common crawl space problems addressed in the remediation projects included: 1. Entry of exterior water due to improper landscaping or poor management of rainwater and snow accumulation. Placement of plants against the buildings contributed to watering and additional moisture loading adjacent to the building. Many crawl spaces showed evidence of exterior water flooding in from below the exterior grade beam.

3 2. Entry of interior water due to sewer line failures, piping leaks or inoperable sump pumps. In some cases, the crawl space contamination was further advanced by the application of hydrated lime, bleach or other chemicals in an attempt by the building owners to control odors in the crawl space and adjacent building areas. 3. The lack of any system to provide an effective environmental separation for the crawl space floor assembly. At best, sheets of polyethylene were layered onto excavations, without any detailed method for attachment or sealing of the edges or penetrations. The addition of a surface layer of sand provided an ideal environment for the retention of moisture and contaminants and prevented any attempts at cleaning. 4. Interior insulation that did not control moisture or air leakage, resulting in significant surface condensation and moisture damage of rim joists and wood framing. In addition to extensive mold growth, rotting and deterioration of the building structure occurred. 5. Contamination of the space by pests, including insects, mice, rats and bats. The extensive placement of poison bait packages contributed to the accumulation of carcasses throughout the space and the presence of poisonous materials scattered in the non-cleanable sand/soil floor surface. 6. Microbial contamination of the space due to mold growth on wetted paper, wood, food containers, air filters, packaging from repair parts and other debris. This was often compounded by piles of garbage left behind and sheets of cardboard or wood placed on the wet floor by service personnel who tried to avoid working on the wet, muddy floors. 7. Physical hazards due to the presence of broken glass, wood, nails, metal shards, abandoned repair parts, electrical components exposed, and other garbage left during construction or by subsequent service personnel. 8. Poorly sealed mechanical equipment (air handlers, cooling/heating coils or fan coils) and ductwork which when located in a contaminated crawl space, provided a significant pathway for the transport of contamination. A number of crawl spaces were directly supplied with air from the building ventilation system. Supply air or air leakage from supply air ducts often resulted in pressurization of the crawl space relative to the main floor and contributed to air transport from the contaminated crawl space. 9. Limited access, restricted movement and poor lighting contributed to difficult and dismal working conditions and reduced any worker commitment to maintaining or improving the space. Remediation strategies Prior to conducting any work in the contaminated areas, a detailed isolation plan, which included extensive sealing of the floor assembly and ventilation system was implemented. Crawl spaces were remediated by following a detailed project plan. A typical set of the remediation tasks that were included in the project plan included: 1. Remove all interior insulation to expose the rim joists and grade beam.

4 2. Remove all debris (garbage, construction materials, etc.) from the crawl space floor. 3. Perforate or remove existing floor barrier membrane (removed all exposed polyethylene sheeting or ground cover membrane). 4. Remove all surface mold using sanding, scraping, and brushing. In some cases, bleach was applied to address rodent contamination issues. 5. Install supports or repairs for deteriorated structural elements. In some cases, deteriorated elements could not be removed and were enclosed and sealed in place. 6. Install a exterior perimeter drainage system at the exterior of the grade beam and connect piping to new, covered and sealed sumps located inside. 7. Provide durable eavestroughs, downspouts and downspout extensions to collect rainwater and move water away from the crawl space exterior. 8. Re-grade the crawl space floor to provide a continuous grade and establish low points at sump openings. 9. Install a new floor barrier attached at the edges using durable and tightly sealed connections. A white, high-density, cross-linked polyethylene barrier material was used to provide significantly better durability than traditional polyethylene sheeting. 10. Install thin rubber mats to establish pathways for inspection and maintenance personnel and to protect the floor barrier in high traffic areas. 11. Conduct detailed cleaning using a HEPA vacuum and damp wiping of all interior surfaces. Although not required for mold clean-up, due to the rodent contamination in cases some contractors spray-applied bleach to many interior surfaces. 12. Install a dedicated crawl space exhaust fan to provide continuous depressurization and ventilation. Although air was not supplied to the crawl spaces, air leakage through the floor assembly provided approximately 0.3 ach -1 at a crawl space depressurization of approximately 3 5 Pa. 13. Excavate the exterior and install rigid polystyrene insulation on the rim joist and grade beam, back fill, and re-grade with a well-compacted clay layer or polyethylene sheeting. Washed gravel or other landscaping surface ballast, rather than plants, eliminated the need for watering adjacent to the building. During the remediation, it was essential that the space remained under a negative pressure to prevent contaminants from entering the occupied areas of the building. Workers were to wear personal protective equipment at all times when on site and contaminated materials were to be removed and properly disposed of. Crawl space remediation projects, and on-site activities were typically completed within 6-12 months.

5 RESULTS AND CONCLUSIONS The results from the study clearly demonstrate that well planned and implemented remediation projects can turn highly deteriorated crawl spaces (Figure 1A) into functional and durable building components, which ensure the long term stability, performance and sustainability of the building (Figure 1B). All of the remediation techniques were successful in returning the crawl spaces to a clean, functional space. Due to the diversity of each of the crawl space issues, a number of strategies required modification in order to meet the needs of the project. Although some strategies proved to be better than others, all the employed methods significantly improved the condition of the crawl spaces. The installation of a durable floor barrier was essential for separating the crawl space from the external environment and preventing external moisture from entering the space. In particular, the white floor barrier is much more durable than some of the original coloured floor barrier options, such as polyethylene sheeting. The white coloured barrier was also easier to visually inspect, as it readily showed signs of staining, leaking and dirt. The overall cost difference between using a high performance barrier material and polyethylene for the completed projects was relatively small, and is recommended. It was noted that semi-aggressive surface bleaching methods had no apparent advantage for removing mold or providing good long-term performance. Bleaching was observed to cause some damage and/or corrosion to nearby electrical wiring or metal. Due to the presence of rodents in some areas, the use of bleach or some other disinfectant was required. In general, it is recommended that basic physical cleaning be conducted for the removal of mold, as it provided good long-term performance. Exterior landscaping and water management were critical elements in preventing basic moisture entry problems. Combining proper surface and sub-surface drainage resulted in complete control of external moisture and no evidence of any entry of moisture from the exterior. Figure 1A:

6 Figure 1B: Figure 1: A) An example of a deteriorated crawl space. Dirty, moldy furnace filters, light bulbs, pieces of insulation and other debris, were present on the dirt/sand crawl space floor. The crawl space floor was damp and did not have an effective floor barrier installed. Piping was installed close to the ground and was deteriorated and leaking. B) An example of a remediated crawl space. The crawl space has been cleaned and a durable floor barrier has been installed to separate the space from the external environment. The floor barrier extends up the concrete piles, and has been sealed at all junctions. Piping has been moved overhead to allow movement within the crawl space. Thin rubber mats have been installed to further protect the floor barrier and provide comfortable pathways for maintenance personnel. DISCUSSION The study found that the failure to recognize the basic performance requirements of conditioned crawl spaces resulted in conditions that compromise the indoor environment and threaten the continuing physical performance and usability of these buildings. Even though many of the crawl spaces were in poor condition, the design of appropriate methods to fix the fundamental issues allowed highly compromised crawl spaces to be remediated to a high level of performance and durability. Regular crawl space inspections and maintenance are essential for keeping building areas clean and in good condition. Although many of the crawl spaces had deteriorated as a result of an underlying building design flaw, many of the crawl spaces experienced additional deterioration as a result of neglect and lack of upkeep. Based on the follow up study results, providing building operator education and supply adequate resources are critical to ensure that crawl spaces receive adequate continuing maintenance. Remediation costs have increased from the 2002 values of $71-134/m 2 (Figley and Sieber, 2002) to consistently over $200/m 2. Although this may seem expensive, the remediation of crawl spaces is an effective strategic investment in extending the overall life of a building, while ensuring that the crawl spaces do not compromise the indoor environment of the building.

7 ACKNOWLEDGEMENTS The authors would like to gratefully acknowledge the assistance of Mr. Don Berton, Mr. Dennis McLain, Mr. Ray Sieber, P.Eng. and Mr. Bob Trefenanko with the Saskatchewan Housing Corporation for their leadership, enthusiasm and support in developing and implementing the crawl space remediation program. REFERENCES ASHRAE ASHRAE Handbook Fundamentals, Chapter 24. Atlanta: American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc. Figley, S. and D. Figley Development and Assessment of Crawl Space Remediation Strategies. Canada Mortgage and Housing Corporation, Ottawa, ON. CMHC CR File No.: 6585-F Figley, D. and Sieber, R Cleanup of Microbial Contamination in Major Building Crawlspaces. In: Proceedings of the 9th International Conference on Indoor Air Quality and Climate Indoor Air Monterey, California, USA. pp National Building Code of Canada Vol.1. Section 9.18, Crawl Spaces. National Research Council of Canada, Ottawa ON.