Heat loss at the entrance of a building can be caused by mechanical ventilation, natural ventilation and natural convection. Descriptions of these losses are given here.
Mechanical Ventilation
When using a mechanical ventilation system, the interior of the building or a zone inside the building can be pressurized in three different conditions. Positive pressurized, negative pressurized or pressurized (no pressure difference between zones). These pressure differences in the openings between zones can be the result of an unbalanced ventilation system, ineffective controls or, in some cases, design. Air curtain solutions can work in these scenarios. However, the highest efficiency is achieved when the pressure difference between zones is zero.
Natural Ventilation
Buildings are not completely airtight. Openings in buildings, such as doors, windows and cracks, naturally allow warm air to escape and cold air to replace it. This natural ventilation can be enhanced by the wind conditions and direction in the door zones. The use of an air curtain in this scenario reduces the effects of heat loss due to wind-driven natural ventilation.
Natural Convection
Cold air is much heavier than warm air, allowing the warm air to rise. Along an undisturbed boundary between a heated space and a cold space, warm air will escape from the top of the opening. This process will naturally cause cooler air to enter the heated space from near ground level, known as natural convection. Under these conditions, an air curtain can limit the air exchange between the two zones by creating a barrier to impede airflow.
Energy Use and Costs
Maintaining a temperature in a region through heating or cooling is costly. This cost can be seen in two ways: the energy required to achieve that temperature and the associated monetary value. The graph below compares the relative costs, both energy and financial, of various options and the consequences of using a suitable or poorly chosen air curtain solution. For businesses with an open door policy in energy use and energy expenditure, the effects of using a properly selected air curtain solution are clearly visible.
