Best Place for for Ducks to Sleep Outside?

[justducky1]

What is the best type of structure for ducks to sleep in at night (for protection and warmth). My pen is about 12 ft. by 12 ft.

 

[Miss Lydia]

What is the best type of structure for ducks to sleep in at night (for protection and warmth). My pen is about 12 ft. by 12 ft.

a few ideas here https://www.backyardchickens.com/t/170341/duck-house-designs/20
https://www.backyardchickens.com/t/752779/the-quack-shack-duck-house-pics