Not through a window. Just not enough light, there.
I live in Alaska and am growing outside very successfully, this year. My first outdoor grow. 
Overwatering comes from not allowing the grow medium to dry out before adding more water. New growers will water based off of nute schedule or medium recommendations.
Flushing requires large amounts of water over a very short lime 90% of which goes right down the drain and pot is allowed to dry out before new water schedule is started.