Lev door (also convection door) is a floor-to-ceiling (full height) internal door, consisting of a standard door leaf and an upper leaf (often standard door leaf cut in half) in place of the usual header wall.[1][2] The leaves may or may not be separated by a transom.
In cold climate, Lev doors enable effective convection of warm air through buildings from central heat sources, such as fireplaces or air conditioning units, without the need for ducting. In warm climate, the doors enable free passage of cooling cross-breezes when the main door leaf is shut. Privacy and air circulation may be controlled independently using this design.[3]
Transom doors are similar in function, however Lev doors are significantly more economical to construct due to their simplicity, while also allowing greater passage of air through their larger unobstructed opening. Dutch doors are similar in configuration, but they differ in design, proportions, hardware and function, being used externally for ventilation, security and exclusion of livestock, while Lev doors are used internally for improved energy efficiency in sustainable architecture.
Vertically divided doors have been in use for centuries, such as Dutch or Irish doors, transom doors, however those were typically external, serving a different purpose of ventilation and security.
Lev doors first appeared as unique design feature in buildings by Australian architect Jiri Lev, who refers to them as convection doors.[1]
In buildings warmed air rises and progressively spreads from the heat source across the ceiling. As it reaches walls and cools down, it begins to descend and return to the heat source, to fill space created there by more heated air risen. Typical door openings do not reach above 0.5 to 1m below ceilings, thus allowing only limited amount of warm air to pass through into other rooms. Lev doors, like other floor-to-ceiling doors, span the full height of the room, enabling warm air to freely continue through.
Measurements indicate temperatures in secondary rooms with typical doors approximately 2-3 °C (3.6-5.4 °F) below those in primary rooms (rooms where heat source is located). Temperatures in secondary rooms with Lev doors are typically equal to those in primary rooms.[4]
Where the lower panel of the door is often kept in the closed position, the full performance of the door can be maintained by a gap or screened opening in the panel close to the floor.
