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 N. C. Closed Crawl Space Demonstration studies Study of closed crawls in 2 other climates

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 Floor: 65 -70 F H 2 O pipes: 55 -65 F

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?

Study Population 45 houses Between 2 - 60 years old Average 27 years

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

Crawl Space Observational Results

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

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)

Visible Mold Examples

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

Average Spore Counts Higher in Crawl than Outdoors # of Houses Outside (CFU/m 3) Crawl space (CFU/m 3) 45 3, 027 19, 102 21 3, 235 30, 163 14 3, 427 16, 041 10 2, 033 161

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 A house return G supply 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 G crawl space E = crawl space to house G and F = outside to ducts A House return supply E B C D Crawl Space F

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

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 * Classification Percent of houses tested <3% <0. 55% Minimal 0 3. 1 -5% 0. 56 -0. 91% Limited 4 5. 1 -8% 0. 92 -1. 46% Moderate 9 8. 1 -12% 1. 47 -2. 19% Excessive 18 >12% >2. 20% Major 65 * Cubic Feet per minute at 25 Pascals

Measured House Leakage and Classification CFM 50 per ft 2 M 3/h/m 2 at 50 of surface Pascals area* Classification Percent of houses tested < 0. 25 <4. 6 Minimal 0 0. 26 - 0. 45 4. 7 -8. 2 Limited 24 0. 46 - 0. 60 8. 3 -10. 9 Moderate 42 0. 61 - 0. 75 11 -13. 7 Excessive 20 > 0. 76 >13. 8 Major 13 * Cubic Feet per minute at 50 Pascals

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

Big Obvious Holes

Percent of total house leakage from crawl space Most homes had at least 10% of their air leakage coming from the crawl space % of total house air leakage # of Houses (45 tested total) 31%-40% 3 21%-30% 13 11%-20% 18 0%-10% 6

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

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

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

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

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

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

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)

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