A method for heating a door guide area includes: channeling a flow of heated air in a longitudinal first direction in a first conduit; channeling the flow of heated air in a longitudinal second direction different than the first direction in a second conduit; providing heated air to the second and first conduits by routing the heated air directly from a heater laterally across the first conduit to the second conduit; transferring heat from the flow of heated air in the second conduit to a heated space outside of the first and second conduits; and configuring a side portion of a roll-up door to be in the heated space when the roll-up door is in a closed position.

A roll-up door assembly includes a first curtain, a second curtain, and a side frame. The first curtain and the second curtain can transition between a lowered position and a raised position. The first curtain and the second curtain at least partially define an internal volume in the lowered position. The side frame includes an elongated body defining a hollow interior, a pair of curtain tracks, a heating assembly, and an inlet assembly. The pair of curtain tracks can guide the first curtain and the second curtain between the lowered position and the raised position. The heating assembly can circulate heated air into the internal volume. The inlet assembly can provide fluid commination between the heating assembly and a lower temperature conditioned space such that the heating assembly can circulate air from the lower temperature conditioned space into the internal volume.