^Mineral oil is much cheaper, but of course it is messy, and after mineral oil bath, your miner's resale value is 0
From what I read, that Novec can actually be used to wash hardware so it would not be problem, but with that, one would need airsealed tank and condenser loop.
http://www.allied-control.com/immersion-cooling/frequently-asked-questions-faqsMineral oil bath can apparantely run with passive cooling, though I don't know, if passive cooling is enough for mining hardware.