# Presentation: 497765

## Crawl Space Research

**Crawl Space Research**
***Managing moisture and saving energy with closed crawl spaces***
***Cyrus Dastur***

## Crawl Space Moisture Problems

## Chances for Above Ground Decay

**Chances for Above Ground Decay**

**Notes:**
Remember that we can re-create a wet climate zone in an otherwise dry climate by adding landscaping, irrigation, etc. Las Vegas, NV can have the same problems as Raleigh, NC!

## Symptom:Light mold spotting incrawl space 

**Symptom:****Light mold spotting in****crawl space **

**Notes:**
Many problems start small. My house is a 65-year-old home that had a vented crawl with no ground vapor retarder until 2003. One of the draws for me to buy this house was its lack of any major moisture problem under the house. Were there problems? Sure: plumbing leak under bathroom, old termite damage due to water problems at attached porch, surface mold on framing, poor storage due to high RH.

## Typical response: Add ventilation

**Typical response: Add ventilation**

## Resulting mold explosion

**Resulting mold explosion**

## Some lumber still good

**Some lumber still good**

## Some lumber rotten

**Some lumber rotten**

**Notes:**
Major structural problems.

## Data was Needed to Understand the Problems and Solutions

**Notes:**
So, from years of experience AE and many others knew that venting crawl spaces with outside air created more problems than it solved. AE and many others also knew anecdotally that properly closing and managing moisture inside a crawl space could solve the problems. However, recommended designs for crawl spaces and the building code were a mine field for contractors and builders attempting to build closed crawl spaces. To fully understand the problem and test solutions we needed data from applied research.

## FundingNational Energy Technology LaboratoryU.S.Department of EnergyThis presentation  was written with support of  the U.S. Department of Energy under Contract No. DE-FC26-00NT40995.  The Government reserves for itself and others acting on its behalf a royalty-free, nonexclusive, irrevocable, worldwide license for Governmental purposes to publish, distribute, translate, duplicate, exhibit and perform this copyrighted presentation.Co-Funding and Project ManagementAdvanced Energy Project Director: Bruce Davis  bdavis@advancedenergy.orgProject Manager: Cyrus Dastur cdastur@advancedenergy.org

## Project Goals

**Research**:  Monitor and compare the thermal and moisture performance of closed vs. wall-vented crawl spaces
- 12-Home Field Study
- 2-Home ORNL Hygrothermal Study
**Technology Transfer**:  Accelerate acceptance of properly closed crawl space systems

## Why add ventilation to a crawl space???

**Ducts: 55-65 F**

**H****2****O pipes: 55-65 F**

**Floor:**
**65-70 F**

**Framing:70-78 F**

**Why add ventilation to a crawl space???**

**Notes:**
Typical summer conditions in Princeville are actually more humid than the example noted above. Daily average dew points range from 70 F to 75 F throughout the summer months.

## Site Elevated for Flood Protection

**Site Elevated for Flood Protection**

**Site Elevated for Flood Protection**

**Notes:**
This development was part of the rebuilding of Princeville (oldest town incorporated by freed slaves in NC) after devastation by hurricane Floyd in 1999.
Site was elevated with uniform fill to reduce future flood risk.

## Homes Complete and Occupied

**Homes Complete and Occupied**

**Homes Complete and Occupied**

**Notes:**
12 houses, six on each side of the same cul-de-sac street.
Identical floor plan built as adjacent mirror images.
All-electric homes with package-unit heat pumps. Duct systems located in the crawl space.
All but one house (military reservist – AE is paying energy bills to keep home in study) are occupied full-time.

## 12 Home Field Study Site

-   103

-    101

- 106

- 108

- 110

-    111

-   109

- 107

-   105

- 104

-       102

-      100

**N**

**Notes:**
ORNL weather station at 106
106 and 110 in ORNL hygrothermal study
Outside conditions monitored at three locations across the site and averaged.

##  Phase I: July 2001 – May 2003

**Notes:**
Note that these are GOOD vented crawls – 100% poly, more ventilation opening than required, highly monitored for water problems.
Vents plugged with rigid foam and sealants, walls air-sealed around package unit penetrations, plumbing entrances, wiring entrances, etc.
All ground covers are secured with sod staples. Liner in closed crawl space sealed with mastic and mesh tape. 
Point out termite inspection gaps. Pest management representatives are some of our strongest allies.
Dehumidifiers used temporarily for initial dry-down, then turned off. Have not been used since.
Duct leakage was the only drying mechanism present in closed crawls in Phase I
Note re: wall-insulated group: AE doesn’t recommend porous insulations on crawl walls as best practice, and definitely would not have them in ground contact. “We were young”

## Data Collection & Monitoring

-  Component air leakage testing
-  Temperature and RH logging
-  Pin wood moisture readings
-  Bio-aerosol sampling
-  Short- and long-term radon monitoring

## Phase I Crawl Space Relative Humidity

**Phase I Crawl Space Relative Humidity**

## Phase I Crawl Space Absolute Humidity

**Phase I Crawl Space Absolute Humidity**

## Phase I Results

**Humidity was controlled in closed crawl spaces and not controlled in wall-vented crawl spaces**
**Utility bill analysis indicated that the closed crawl space houses might be saving energy on heating and cooling (even with 4 uninsulated homes!).**

## New Phase Begins in June 2003

- Sub-metered all heat pumps
- Air-sealed all floors and crawl space ductwork
- Re-measured component leakage
- Provided HVAC supply air in closed crawls*(1 cfm per 30 square feet)*
- Modified closed crawl space insulation systems

## Phase II: June 2003 – June 2004

**Wall vented**
**R-19 Floor**

**Closed**
**Sealed liner**
**R-19 Floor**

**Closed**
**Sealed liner**
**R-13 Wall**

**Wall vented**
**R-19 Floor**

**Closed**
**Sealed liner**
**R-19 Floor**

**Closed**
**Sealed liner**
**R-13 Wall**

**Notes:**
Note that batt insulation could be used in the band of wall-insulated crawl spaces for faster install and easier inspections by pest control operators.

## Crawl Space Supply Air Duct

## Phase II Crawl Space Dew Points

**Phase II Crawl Space Dew Points**

## Phase II Crawl Space Relative Humidity

## Summer RH Summary

**Summer RH Summary**

**Notes:**
As fate would have it, 2002 shows crawl spaces in best-case scenario, since this was a record drought year in NC
2003 shows crawl spaces in worst-case scenario, since this was a record-setting year for rain in NC
Data is based on daily average numbers for the different experiment groups. Both closed groups are shown together.
The blip of 5% of days over 70% in closed crawl houses was a result of the experiment changeover from Phase I to Phase II. As soon as the crawls were re-closed and the supply ducts opened, moisture levels were controlled.

## Phase II Average Wood Moisture Content

## Seasonal Total Energy Use

|               Season | Floor Insul | Wall Insul |
| --- | --- | --- |
| Summer | -22 % | -36% |
| Fall | -5 % | -10% |
| Winter | -10% | +4% |
| Spring | -19% | -28% |
| Total | -15% | -18% |

## Next Steps:Technology Transfer

*Implementing practical changes for large moisture and energy benefits*
- Closed crawl space construction guides
- Fact sheets and research results
- Design and analysis tools
- Code language

## Next Steps: Construction Guides

**Next Steps: Construction Guides**

## Next steps: Future research

- Extend energy and moisture research to new regions and house geometries
- Test and measure new drying methods
- Test new component products
- HUD study: Is there a health connection?
- Duke study: Vented crawl spaces as sources of indoor air contaminants

## Next Steps:Product Development

- Structural support
- Air leakage retarder
- Capillary retarder
- Vapor retarder
- Pest management solution
- Thermal insulation
- Fire protection

## Six Implementation Issues

- Overcoming “physics- and logic-free zones”
- Applying codes; working with code officials
- Choosing a design
- Pricing closed crawl space work
- Managing labor: safety, skills, pay
- Managing moisture and job-site logistics

## Six Design Issues

- Pest control
- Moisture control
- Fire standards
- Thermal standards
- Combustion safety
- Radon control

- Provide combustion air!
- Tjernlund.com
- Fieldcontrols.com

## Proceed with Care!

**Proceed with Care!**

- Closed crawl spaces are robust and tolerate flaws, but are not a silver bullet
- We can (and do) mess them up just like everything else in construction
- Moisture must be managed during the construction process!!

## Thank You!

- Advanced Energy
- Raleigh, NC
- www.advancedenergy.org
- www.crawlspaces.org