Interesting, so in Winter, say the outside temp is 20F and inside temp is 69F, that's a 49F difference. In Summer, say the outside temp is 85F and the inside t

Interesting, so in Winter, say the outside temp is 20F and inside temp is 69F, that's a 49F difference. In Summer, say the outside temp is 85F and the inside temp is 68F, a 17F difference. Maybe I'd get at best 50% heat recovery in the Winter and 25% in the Summer? That's a lot better than no recovery. I like the aluminum plate idea, maybe two big heat sinks with long fins attached back to back with the air blowing through the fins would work better and be cheaper. I like the fact that the CPU coolers are somewhat plug and play though, the fans are already integrated and power supplies are easily available. Both approaches are fairly easy and cheap to try. Wikipedia offers some insight on heat pipes: https://en.wikipedia.org/wiki/Heat_pipe https://en.wikipedia.org/wiki/Heat_pipe So what is the working temperature range for CPU cooler heat pipes? Though they maybe be optimized for 100F temperature difference, CPU's also don't always run at full speed and maximum power. So perhaps CPU coolers would still be useful at lower temperature differentials (and lower absolute operating temperatures.)