If you put a iron bar in front of a encased fan it will blow through the fans. If you are to use Create Deco bars this does not take effect.

It appears that adding the FAN_TRANSPARENT tag should fix this: https://github.com/unascribed/Create-Fabric/blob/mc1.18/fabric/dev/src/main/java/com/simibubi/create/AllTags.java#L111>

This was tested on the fabric version of create.