My incubators are old fridges with computer fans screwed to the bottom for air movement a vent cut in the side down the bottom with another computer fan to turn on if it gets to hot as i live in Adelaide and dont have very good airconditioning in my house, a 9m heat cord wound into the bottom wire shelf for heat and a digital readout thermostat so i can tell inside temp freezer doors pulled off for this is where all the wirin and thermostats are so my 5 yr old cant get to them and these have worked well for a number of years. as being fridges they are well insulated and if they arent working people are happy to give them to you, also because of the shelving you can get slightly different temp variables for certain species.