I think it depends on the type of window too. The concern is temperature fluctuations. Even with a heater, it can easily overheat in the summer (the heater only doesn't make it cold, but doesn't really keep it from heating), and plummet down at night. How bad is it, I'm not sure, however the logic's there. But there are windows that don't allow such temperature changes, but I don't nkow what they are.
And I've been told that indirect sunlight will cause lots of issues still (but if you have a background, I think taht should be fine). Beware of algae though, I foresee some trouble, haha.