Improvements in building technology have increased the interest in closed crawlspaces. The energy-saving option isn’t reserved for new homes, but can also be applied to existing homes, which can be retrofitted.
So how do you “close” the crawlspace? There are two primary closed crawlspace methods: the wall insulated system and floor insulated system. In new construction and in a retrofit of an existing homes where there is no floor insulation, the system includes: closing and sealing the foundation vents; sealing around all plumbing, HVAC and electrical penetrations; and installing a thick moisture barrier on the exterior walls and around all piers. Finally, rigid foam insulation is installed on the exterior walls of the crawlspace (rather than in the floor joist). A supply duct from the existing HVAC system is installed to allow for conditioned air to flow into the crawlspace. This reduces humidity and the temperature difference between the home and the crawlspace.
In retrofits, where floor insulation is already installed, the installation method is essentially the same. The exception is that the existing insulation is left in place in the floor joists and the exterior walls are not insulated.
One word of caution here — if the crawlspace houses an appliance such as a gas or oil furnace, or a gas hot water heater, additional provisions will be needed. You cannot seal a crawlspace that houses a furnace or water heater without proper ventilation to the outside and the introduction of new air from outside.
The cost to install a closed crawlspace system in new construction will be approximately $2.50 to $2.75 per square foot of crawlspace area. To retrofit an existing home, expect to spend around $3 to $3.50 per square foot of crawlspace area.
According to Billy Tesh, owner of Pest Managements Systems Inc., a Greensboro company that provides services including closed crawlspace installation, the cost to close the crawlspace of an average-sized home will range from $2,000 to $3,000.
In addition to virtually eliminating stack effect and improving the quality of your indoor air, significant savings on energy bills can be expected. In new construction, studies from Advanced Energy, a nonprofit founded by the N.C. Utilities Commission to investigate and implement new technologies for energy efficiency, found that a closed crawlspace can lead to energy savings of 15 percent to 18 percent. (For additional information on the Advanced Energy studies, visit www.advancedenergy.org.)
For existing homes, the energy savings can be considerably higher — up to 50 percent in some cases. Many older homes do not have any insulation in the crawlspace at all. By insulating and closing the crawlspace, the load on the HVAC system is reduced. Additionally, the stack effect in an older home can be significantly higher because the home has more leaks and places for air to enter.
There are several reasons to seal a crawlspace: Research confirms that closing the crawlspace can greatly improve moisture control and result in significant energy savings to the homeowner, while indoor air quality can be improved by reducing or eliminating “stack effect.”
Scott Allred is chairman of the Triad Green Building Council and owner of Precept Construction. He can be reached at scott@preceptconstruction.com or 286-6811. For additional resources on green building, visit www.preceptconstruction.com or www.triadgreenbuilding.org.
