In which construction type are there direct vertical channels in the exterior walls?

The correct choice is balloon frame construction, which is notable for its vertical channels extending from the foundation to the roofline within external walls. This construction method employs long wooden studs that run continuously from the sill plate at the base of the wall to the top plate at the roof. This design allows for large vertical openings in the walls, which can facilitate the rapid spread of fire, as flames can travel unobstructed through these vertical channels.

Balloon framing was commonly used in building construction up until the 20th century and is an important consideration in fire fighting because it affects how a fire can spread throughout the structure. The long, continuous framing members create a chimney effect, making it crucial for firefighters to understand this type of construction when assessing fire behavior and developing strategies for containment.