A rotary wheel assembly is configured for use with a system for conditioning air to be supplied to an enclosed structure. The rotary wheel is configured to be positioned within a supply air stream and an exhaust air stream. The assembly includes a cassette frame, a wheel rotatably secured within the cassette frame, and a self-adjusting seal subassembly configured to maintain sealing engagement with respect to a surface of the wheel. The self-adjusting seal subassembly includes at least one seal member.