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North Carolina Crawl Spaces – Vented and Closed

North Carolina Crawl Spaces – Vented and Closed. ACI Home Performance 2008 Melissa Malkin-Weber. Presentation Overview. How does the wall vented crawl work? Study Findings Moisture conditions and mold Air pathways Driving forces Transmission of mold to living space

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North Carolina Crawl Spaces – Vented and Closed

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  1. North Carolina Crawl Spaces – Vented and Closed ACI Home Performance 2008 Melissa Malkin-Weber

  2. Presentation Overview • How does the wall vented crawl work? • Study Findings • Moisture conditions and mold • Air pathways • Driving forces • Transmission of mold to living space • N.C. Closed Crawl Space Demonstration studies • Study of closed crawls in 2 other climates

  3. The Myth of Vented Drying 85 F 60% RH 70 F DP Framing:70-78 F Ducts: 55-65 F 73 F 90% RH 70 F DP H2O pipes: 55-65 F Floor: 65-70 F

  4. Crawl Space Characterization Study Objectives • What conditions in vented crawl spaces Southeast U.S.? • Moisture / mold → poor home IAQ? • Are vented crawl spaces delivering mold into house?

  5. Study Population 45 houses Between 2 - 60 years oldAverage age 27 years

  6. Detailed Characterization Protocol • Observational • Wood moisture • Fungal sampling • Building Pressure Diagnostics • Measure fungal transmission to the living space

  7. Crawl Space Observational Results

  8. Moisture Data – Mold Conditions • Puddles in on top of vapor retarders– 42% • Visible moisture discolorations in crawl space — 49% • Evidence of wetting and drying cycle • Visible mold — 62% of homes

  9. Moisture Data – Wood Rot Conditions • Visible wood rot — 47% of homes • Wood moisture content >25% seen in over 1/3 of homes (supports wood rot) • Wood moisture content >19% seen in another 36% of homes (mold supporting)

  10. Visible Mold Examples

  11. Mold Sampling Results In Crawl Spaces • ~ 6 times the concentration of colony forming units in the crawl space than outdoors • Vented crawl spaces are wet enough to support mold growth, and stay wet long enough for mold to establish

  12. Average Spore Counts Higher in Crawl than Outdoors

  13. A house return supply G E B C D crawl space F Is there a connection between crawl space and living space? Pressure tap setup measured pressures: A = outside to house B = outside to crawl space C and D = ducts to crawl space E = crawl space to house G and F = outside to ducts

  14. A House return supply G E B C D Crawl Space F Is there a connection between crawl space and living space? Pressure tap setup measured pressures: A = outside to house B = outside to crawl space C and D = ducts to crawl space E = crawl space to house G and F = outside to ducts

  15. A house return supply G E B C D crawl space F APT: Pressure tap setup measured pressures

  16. Measured Duct Leakage and Classification

  17. Measured House Leakage and Classification

  18. Connection between home and crawl space • Mean equivalent hole size in crawl space connected areas: • in floor over crawl space 8 x 9 inches • in crawl space ducts 6.4 x 9 inches

  19. Big Obvious Holes

  20. Percent of total house leakage from crawl space Most homes had at least 10% of their air leakage coming from the crawl space

  21. Connection between home and crawl space Driving Forces that move air between house, crawl, and ducts • HVAC equipment • Stack effect • Wind • Power attic fans

  22. Summary of Findings Wall vented crawl spaces have • high levels of moisture • higher amounts of mold spores than outside • holes to the living space • forces across the holes

  23. Mold Species Measures Confirm Transmission from crawl to house • Analysis of fungal spores • Species and rank order • HVAC off and on • 47% of houses had transmission from crawl to house

  24. A Robust Solution to the Vented Crawl Specifications at www.crawlspaces.org

  25. Closed Crawl Spaces Provide Dry Foundation and Energy Savings • Properly closed crawl space > Air seal floor and HVAC ducts • Substantially drier • Less potential for mold • Less potential for wood decay • Less potential for insects • 15 to 18% lower HVAC energy use per year

  26. Lets Be Safe Out There! • 20,000 lung cancer deaths /year related to radon (U.S. EPA) • Always test for radon • Especially in closed crawl spaces

  27. Citation Information Paper from ASHRAE IAQ Conference • Malkin-Weber, M., J.Coulter, T. Dixon, C. Dastur and B. Davis. 2007. Vented crawlspaces as mold amplification and delivery systems? Measured performance and a dry alternative.  Indoor Air Quality 2007: Healthy and Sustainable Buildings (on CD) • available at www.crawlspaces.org (follow link under Technical Reports)

  28. Thank You Melissa Malkin-Weber mweber@advancedenergy.org www.advancedenergy.org 919 857-9000 [phone] 919 832-2696 [fax] 909 Capability Drive, Suite 2100 Raleigh, NC 27606-3870

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