Definitely keep it in the house, if that is where your most constant temps are. The suggestions for keeping it away from direct sunlight or drafts are also key, but keep in mind that depending upon the type, some airflow will be important. Keeping it in a space with stagnant air, won't help a still-air incubator, for instance. You need some bit of airflow for temperature and humidity regulation with the air vents. Good luck!