Illustrated Architecture Dictionary
A porch or room having open sides or many windows arranged to permit sleeping in the open air.
Sleeping porches first gained popularity at the turn of the 20th century. Many people believed that fresh air helped sufferers of tuberculosis, a respiratory system illness that was the leading cause of death at that time in our country's history. Health experts then also touted the benefits of fresh air for avoiding other illnesses.
Before the advent of air conditioning, families often created sleeping areas on outdoor porches, where children would sleep during the warmer months.
The porches are often included in the front and back of the home, specifically on corners so as to have access to breezes from all different directions. However, a sleeping porch is often upstairs.
In Queen Anne style houses, often acess to the sleeping porch is through a window - not a door.
There was a 1929 movie entitled The Sleeping Porch directed by Leslie Pearce and starring Raymond Griffith.
Examples from Buffalo: