Closed Crawl Space Performance: Proof of Concept in the Production Builder Marketplace

Abstract

This overview is intended to be a very concise, limited summary of the key project activities discussed in the detailed report that follows. Due to the large scope of this project, the detailed report is broken into three individually titled sections. Each section repeats key background information, with the goal that the sections will eventually stand alone as complete reports on the major activities of the project. The information presented herein comes from ongoing research, so please note that all observations, findings and recommendations presented are preliminary and subject to change in the future. We invite and welcome your comments and suggestions for improving the project. Advanced Energy completed its first jointly-funded crawl space research project with the Department of Energy in 2005. That project, funded under award number DE-FC26-00NT40995 and titled 'A Field Study Comparison of the Energy and Moisture Performance Characteristics of Ventilated Versus Sealed Crawl Spaces in the South' demonstrated the substantial energy efficiency and moisture management benefits that result from using properly closed crawl space foundations for residential construction instead of traditional wall vented crawl space foundations. Two activities of this first project included (1) an assessment of ten existing homes to document commonly observed energymore » and moisture failures associated with wall-vented crawl space foundations and (2) a detailed literature review that documented both the history of closed crawl space research and the historical lack of scientific justification for building code requirements for crawl space ventilation. The most valuable activity of the 2005 project proved to be the field demonstration of various closed crawl space techniques, which were implemented in a set of twelve small (1040 square feet), simply designed homes in eastern North Carolina. These homes had matched envelope, mechanical and architectural designs, and comparable performance characteristics with regard to infiltration and duct leakage. Researchers settled on two closed crawl space designs, one with insulation located in the framed floor structure above the crawl space and one with insulation on the crawl space perimeter wall, as the designs with the most widespread potential for application. Researchers based this assessment not only on the field performance, but also on input from residential builders, pest control professionals, code officials, installers, and building scientists active in the region. The key findings from the field demonstration were that (1) closed crawl spaces stay substantially drier than traditional wall-vented crawl spaces during humid climate conditions, and (2) the houses built on the closed crawl space foundations saved, on average, 15% or more on annual energy used for space heating and cooling. A comparison of the actual energy performance of the homes versus the performance predicted by a popular HERS software application showed that the software was unable to predict the demonstrated savings, in some cases predicting an energy penalty. Findings from the 2005 project were summarized in a publication titled Closed Crawl Spaces: An Introduction to Design, Construction and Performance. Since its release, the publication has received widespread use by builders, homeowners, installers and code officials concerned about crawl space construction. The findings were also used to create major revisions to the NC Residential Code, which were adopted in 2004 and immediately began to reduce the regulatory barriers to widespread commercialization of the technology in NC, particularly in new residential construction. Full project details are located at www.crawlspaces.org.« less