Just isolate your rigs from ambient temp. for ex. if You are building your rigs in a casing then put some kind of mnifold intake to one side of your rigs case and let it breath ex. from outside of your rig-house/room then lead some tube outlet (hot air) to other room or other side keeping some distance between intake and outlet. You may let your cards breath air from the room you keep them, but you necessarily need to lead hot air flow out from your rig environment for ex. fan on your house vent tubing or something.

The worst thing to do when building rigs is building them like most popular now on free-standing opened frame, cuz you need to keep that environment clean off dust, good air quality and specified humidity. The best thing for it is building air-flow-case like server cases are done.

Kindly Regards