Conditioned crawlspaces perform better than vented crawlspaces in terms of safety, health, comfort, durability and energy consumption. Conditioned crawlspaces also do not cost more to construct than vented crawlspaces. Existing vented crawlspaces are experiencing serious moisture and mold problems and are costing builders and homeowners significant resources to repair. Despite the obvious problems with existing vented crawlspaces and the obvious benefits of conditioned crawlspaces there is not a significant trend towards the construction of conditioned crawlspaces. One of the reasons typically cited by builders and designers is “the code does not allow me to build unvented crawlspaces.” This is both generally correct and misleading. The model codes do not allow the construction of “unvented” crawlspaces – except in very limited circumstances, but they do allow the construction of “conditioned” crawlspaces. The distinction is important and necessary. Four conditioned crawlspaces were constructed and monitored over a 12-month period. The data is presented and used to support the current code requirements for the construction of conditioned crawlspaces.