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. Ducts: 55-65 F H 2 O pipes: 55-65 F Floor: 65-70 F Framing: 70-78 F 85 F 60% RH 70 F DP 73 F 90% RH 70 F DP The Myth of Vented Drying

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 old Average 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 # of HousesOutside (CFU/m3) Crawl space (CFU/m3) 453,02719,102 213,23530,163 143,42716,041 102,033161

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

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

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

16. Measured Duct Leakage and Classification CFM 25 per ft 2 of conditioned floor area * M 3 /h/m 2 at 25 Pascals of conditioned floor area * ClassificationPercent of houses tested <3%<0.55%Minimal0 3.1-5%0.56-0.91%Limited4 5.1-8%0.92-1.46%Moderate9 8.1-12%1.47-2.19%Excessive18 >12%>2.20%Major65 * Cubic Feet per minute at 25 Pascals

17. Measured House Leakage and Classification CFM 50 per ft2 of surface area* M3/h/m2 at 50 Pascals ClassificationPercent of houses tested < 0.25<4.6Minimal0 0.26 - 0.454.7-8.2Limited24 0.46 - 0.608.3-10.9Moderate42 0.61 - 0.7511-13.7Excessive20 > 0.76>13.8Major13 * Cubic Feet per minute at 50 Pascals

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 % of total house air leakage# of Houses (45 tested total) 31%-40%3 21%-30%13 11%-20%18 0%-10%6 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. Mean Spore Count by Location # of HousesOutside (CFU/m3) Crawl space (CFU/m3) Crawl space molds in home? 453,02719,102 825 HVAC off 1061 HVAC on 213,23530,163 Definite (47%) 861 HVAC off 1761 HVAC on 102,033161 No (22%) 1323 HVAC off 645 HVAC on 143,42716,041 Possible (31%) 55 HVAC off 176 HVAC on

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

26. 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

27. 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

28. 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)

29. 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 Thank You