The secret garden is protected and likely gets some radiated heat from the building in the
cold months. How much sun infiltrates the space as the sun sits lower in the southern sky I have yet determine but think the upper portion of the north wall should get some . That should provide heat and reflected light that a green house could capitalize on. Broccoli, cabbage,
and lettuce might be possible to grow throughout the winter.
in the summer. Hanging plants could be supported in the upper portion of the structure where they would catch winter light. Even in the summer the structure would provide vertical growing possibilities.
One of the gutters units could be enclosed as a germinating location in early spring.
Going to put numbers on one unit and my hunch is it would not cost that much if done right.
Inspired by the Man of La Mancha. :) Richard T. and Shannon C. suggested 60 degree angle for roof line so that's what it has.