For an active radon mitigation system, is there any reason the inline fan couldn\'t be located in the basement mechanical room as opposed to the attic, if it was necessary? I will check the EPA web site but thought you may have come across this before.
To be clear, a fan is not required as part of EQ 9.1 - it only refers to passive radon resistant construction techniques. Applicable Internationally. Generally, it is best practice to have the fan at the edge of the envelope to prevent pressurizing the exhaust pipe, which can create a greater risk of radon entry into the home in the event of a system leak. Having the fan outside the envelope can increase the risk of failures, especially in cold climates. In every case, the fan should be in a place that is accessible, in case of failures. Once a fan is installed, be sure to seal the exhaust pipe and test for leaks. Refer to the EPA site and the EEBA Guides for more information.
Updated 10/1/13 for rating system applicability.