The principle of using a current of air as an invisible “barrier” between hot and cold zones in entrance areas originated in Europe, where advanced heated duct systems are constructed using powerful blower fans in the ceiling and extraction grids in the floor. However, these systems are often use lots of energy, and are expensive to install and operate. Enershield Air Barriers have evolved this concept to offer maximum efficiency, minimal costs, and simple installation.
An Enershield Air Barrier creates an effective seal on the doorway by re-circulating facility air in a smooth laminar flow, preventing outdoor air penetration. The air velocity from the Air Barrier must be significant enough that the resulting air velocity is directed downwards. The Air Barrier should be set so that a small part of the air stream is directed out of the opening, while the rest blows into the premises. This way, the unwanted outside air is kept out, while the conditioned indoor air is retained inside.
Energy loss through an open door depends on:
- The pressure difference between outside and inside.
- The temperature difference between outside and inside.
- The wind forces on the door opening.
In facilities where ventilation systems are installed, it is vital that the system is balanced (with the same amount of air taken out as put in) to reduce the pressure difference over the door openings.
The less-dense indoor air and the denser outdoor air generate a pressure distribution (b). Cold air flows in through the lower part of the door while warm air moves out through the upper part. The overall airflow increases according to the temperature difference. When the wind blows against the door, air flows into the building, creating a current that is equally large in the whole opening (a). The total airflow through the door is the sum of these effects (c).
Enershield Air Barriers generate a powerful airflow across an open doorway. The kinetic energy in the moving air creates a barrier, like a waterfall, preventing the leakage of air between two areas with different pressure and climate. The smoother the airflow, the harder it is for outside air to penetrate the airflow. Enershield Air Barriers strength follows the formula: mass times the velocity squared. Therefore, an Air Barrier blowing at twice the speed has four times the wind-stopping capability at the same air volume.
To ensure optimal use, approximately 10-15% of the airflow should be directed outwards into the open air. This “loss” is necessary to prevent cold draughts from occurring near the floor, as illustrated in (c). The air velocity near the floor should be approximately 244mtrs/min (3-4 m/s).
Open doors contribute significantly to energy loss in a building. A professionally installed Enershield Air Barrier can reduce energy loss through the door by as much as 90%. In the summer months, Enershield Air Barriers will keep your cool conditioned air inside, hot air out and prevent the ingress of insects, odours and other contaminants such as dust.
During the winter months, Enershield Air Barriers prevent cold draughts, allowing facilities to keep their doors open for extended periods during these colder months. This creates a more comfortable work environment for the occupants and saves energy. It has also proven beneficial in certain situations to enhance manufacturing processes where atmosphere and temperature are critical, such as cold storage areas and freezer rooms.
