Air-gapping is really the only way to stay secure. Plus, I would worry about cameras, microphones and vibration monitors, so I would want to put the air-gapped machine in a room that is away from any other electronics. Ideally in some sort of faraday cage, or at least located a reasonable distance away from walls - to bring it up to TEMPEST (or similar) standards. Unfortunately, most of us do not have the space in our homes to do it properly, so we have to resign ourselves to losing control of our machines and our data.