Closed crawl spaces do double duty as a moisture solution ...

1 RESEARCH UPDATELast year we reported on Closed crawl spaces as a technologythat can dramatically improve the control of moisture in crawlspaces (PCT magazine, June 2003). Closed crawl spaces representboth a new business opportunity and a risk management tool for pestmanagement firms, as the increase in complaints and legal actionrelated to mold growth in homes has made homeowners, tenants andthe home construction industry much more aware of the need tocontrol moisture in homes. A growing number of homeowners andbuilders are investing the additional time and money required toinstall Closed crawl spaces in both new and existing homes.

2 In NorthCarolina, where we have a humid climate and plenty of termite risk,more than 16,000 homes are built on a crawl space every , more than 250,000 new homes per year are built on acrawl space , with an estimated 26 million crawl space homes existingnationwide. The latest findings from Advanced Energy s PrincevilleClosed crawl spaces do double duty as amoisture solution and as an energy saver,according to research out of North Cyrus Dastur and Bruce DavisFigure 1 (top). This wall-insulated Closed crawl spaceuses 2-inch thick, foil-faced polyisocyanurate insula-tion.

3 The foam plugs in the band could be replaced bysections of R-19 batt insulation. A termite inspectiongap is visible at the top of the wall 2 (bottom). This floor-insulated Closed crawlspace has a termite inspection gap at the top of thevapor retarder. Note that penetrations are thoroughlysealed with 3 (left). The butterfly damper of this crawlspace supply opens while the system is running. Theassembly is sealed with mastic and supported bystrapping to ensure long-term proper operation ofthe butterfly 1 crawl space Research project point to an-other benefit of Closed crawl spaces : a signifi-cant reduction in the amount of energy neededto heat and cool homes built on this im-proved foundation following is a review of this research,which may be helpful to pest control firms thatwork in or close crawl spaces for space RESEARCH.

4 Building pro-fessionals have long recognized that crawlspaces are prone to moisture problems andalso may waste energy. In 1994, a nationalsymposium on crawl space moisture prob-lems concluded that crawl spaces are danger-ously wet. In 1998, William Hill, a researcherat Ball State University, reported on theenergy wasted in vented crawl the spring of 2001, Advanced Energybegan a research project in the eastern NorthCarolina town of Princeville to compare themoisture and energy performance of closedcrawl spaces to that of wall vented crawlspaces.

5 Another main goal of the project is todemonstrate the practical application of closedcrawl spaces using straightforward processesand readily available tools and materials. Co-funded by the Department of Energyand Advanced Energy, the project is directedby Bruce Davis and managed by Cyrus Dasturof Advanced Energy in Raleigh, Theproject team includes Dr. Achilles Karagiozis,Oak Ridge National Laboratory; Dr. WayneThomann, Duke University; Dr. JohnStraube, University of Waterloo, Canada;Architect Bill Rose, University of Illinois atChampaign-Urbana; Dr.

6 Joe Lstiburek,Building Science Corp.; Physicist AntonTenWolde, Forest Products Labora-tory; Environmental Scientist Terry Brennan,Camroden Associates; and Project Consult-ant Bill Warren, Bill Warren Energy 12 homes studied in this project arelocated in the same development, with sixhouses built side-by-side on each side of onestreet. All are the same size at 1,040 squarefeet, with the same floor plan and windowschedule (see Figure 4 above). After seeing thepotential for energy savings during a billinganalysis in early 2003, we outfitted all 12houses with electric sub-meters to recordexact energy consumption by each home spackage-unit heat pump system (see Figure 6on page 4).

7 We reduced duct leakage and house leak-age to comparable levels across all the deficiencies were corrected in allhouses and heat pump refrigerant charge andsystem airflow were measured to be consis-tent among all houses. All the houses have afresh air ventilation intake integrated withthe HVAC ductwork. A 6-inch insulated flexduct from outside routs air through a 1-inchpleated media filter and then connects di-rectly to the return plenum. Whenever theHVAC system is operating, 40 cubic feet perminute (cfm) of filtered fresh air is mixed intothe return air stream, conditioned, then dis-tributed to the 12 homes in the study are brokeninto three groups of four homes each: onecontrol group and two experimental four control houses have conventionallyvented crawl spaces , with 11 8-inch by 16-inch foundation vents.

8 Although the build-ing code allows a reduction in the amount ofwall venting when a ground vapor retarder ispresent, all 11 foundation vents were re-tained (see Figure 5 on page 3). (CurrentNorth Carolina code would not require theground vapor retarder since these vents pro-vide the net free area to meet the 1:150ventilation requirement.) Each house has a 6-mil polyethylene ground cover that is me-chanically secured to the soil with turf seams are lapped approximately 6 inchesbut are not sealed. The ground cover extendscompletely to the foundation wall and inter-mediate piers, covering 100 percent of thesoil.

9 The floors of the control houses are in-sulated with R-19 Kraft-faced fiberglass crawl space vents of the experimenthomes were sealed with rigid polystyrenefoam and mastic or spray foam. Each of theseclosed crawl space houses has a sealed, 6-milpolyethylene liner covering the floor andextending up the foundation wall to a height3 inches from the top of the masonry. Theseams of the liner are sealed with fiberglassmesh tape and mastic and the edges are sealedwith mastic to the foundation wall or inter-mediate piers. The liner is mechanically se-cured to the soil with turf staples and to thefoundation wall with a furring control in the Closed crawl spacesis provided by a small duct that provides 35cfm of air to the crawl space from the supplyplenum whenever the air handler is running(see Figure 3 on page 1).

10 No fan-timing or fan-cycling controls are used in the mechanicalsystem and no stand-alone dehumidifiers areused for moisture control. A balancing damperpermits adjustment of the flow and a back-flow butterfly damper prevents movement ofair from the crawl space into the supplyplenum when the system is of the Closed crawl spaces are insu-lated with R-19 Kraft-faced fiberglass batts(see Figure 2 on page 1) in the floor above thecrawl space and the other four are insulatedwith 2 inches of R-13 foil-faced poly-isocyanurate foam (see Figure 1 on page 1) onthe perimeter wall and on the band joist.