Originally, the solar heated pig house (aka barn) covered only half of the southern-facing portion of the roof. The success of that setup led to its expansion to the whole south face.
PHOTO: JIM MURPHY
This interior view of the farrowing house shows one of the fan-controlling thermostats (the second thermostat is inside the collector), the temperature gauge, and the outlet for the hot air duct.
John Feyen and Sharon Murphy install support ribs for the second half of the collector. Note how the pig-raisin' people have cleverly—and economically—used the original roof of the barn as part of their collector! The lumber comes from trees cut on their own land, and the ductwork is made of inexpensive pressed board, so the biggest material expense was for the fiberglass resin skin (the film used in the first collector cost $270).
The manifold is about one foot square (slightly larger ductwork might work even better) and carries the heated air into the barn through a farrowing house window that once held an exhaust fan.
Cross-sectional diagram shows materials, dimensions, and the path of air convection through the structure.