I received my Anova last week, and picked up a Cambro-style food box to use with it. The amount of heat and evaporation loss was pretty obvious the first time I used it, so I decided to modify the lid to fit around the circulator, and to add some Reflectix insulation. Inspired by Alan's excellent video, I tried to document the process; unfortunately I lack his videography skills, so I instead put some photos and instructions into a flickr set here: http://flic.kr/s/aHsjPasH54. The flckr UI is perhaps not ideal for this purpose, but each photo does include a description of the steps taken. The result provides a noticeable improvement in heat retention. The time taken for the Anova to raise the water from 25C to 60C went from 36m22s for the uninsulated box down to 33m8s once it was insulated (I forgot to measure the exact volume of water, but I'd estimate it was somewhere around 15 liters). I also measured the heat loss of the uninsulated box with no lid, starting at 60C, and found it dropped to 47.8C after one hour, 40.7C after two hours, 36.0C after three hours, and 33.0C after four hours. The water had returned to the 25C ambient temperature in under 10 hours. In contrast, the fully insulated box (lid fitted and a piece of Reflectix insulation floating on the water) only dropped to 58.1C after an hour, 56.1C after two hours, 54.0C after three hours, and 52.1C after four hours. It was still in the mid 30s after 24 hours. Evaporation seems to be well controlled, too: I've been cooking some ribs at 60C for the past 18 hours, with no perceivable drop in the water level. One thing to note about the Reflectix insulation: the manufacturer's website rates it for use in environments up to 82C, so floating it on the water should be fine for the temperatures typically used for long cook times; but I wouldn't recommend that at the higher temperatures used for things like vegetables. Fortunately, those generally require much less time, and thus evaporation isn't a big concern.
