North light, and how to keep it
The most valuable material in a room is usually the one nobody paid for.
North light is even, cool and almost unchanging through the day. Painters have built studios around it for four hundred years. Most homes waste it on a spare room.
Do not block it
The most common mistake is storage under the window, which raises the visual floor of the room and cuts the light exactly where it is most useful. Keep everything below sill height, or move it to the opposite wall.
Do not correct it
North light is blue, and every instinct says to warm it up with lamps. Resist for a week. Rooms that are allowed to stay cool during the day feel considerably warmer at night.