Lev door

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.

[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.

[1] In buildings warmed air rises and progressively spreads from the heat source across the ceiling.

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.