This configuration is feasible for new construction, but difficult to implement in existing buildings. The Czech BIM Council, established in May 2011, aims to implement BIM methodologies into the Czech building and designing processes, education, standards and legislation. Air doors work best when the pressure differential between the inside and outside of the building is as close to neutral as possible. Air doors are designed to fully cover the width of a doorway, whereas overdoor heaters may be too narrow. The discharge nozzle on an air door is optimized to provide a uniform air stream across the whole width of the doorway, which may not be the case with overdoor heaters. The Air Movement and Control Association (AMCA) defines an air curtain as: "A directionally-controlled airstream, moving across the entire height and width of an opening, which reduces the infiltration or transfer of air from one side of the opening to the other and/or inhibits flying insects, dust or debris from passing through". Heated air doors are commonly used when supplemental heat is needed for a space, and to reduce the wind chill factor inside the opening, in colder climates. The most effective air door for containing conditioned air inside a building with an open door will have a high face velocity at the opening, generated by top-down flow, and air recovery by a recirculating air plenum and duct return to the source fans.
Where a large volume of hot gas is available from some process, a heat recovery steam generator or recovery boiler can use the heat to produce steam, with little or no extra fuel consumed; such a configuration is common in a combined cycle power plant where a gas turbine and a steam boiler are used. Negative pressures, extreme temperature differences, elevators in close proximity, or extreme humidity can reduce the effectiveness of air doors. Under ideal conditions of zero wind, the effectiveness of the air door is at its maximum, but in windy locations air doors cannot create a perfect seal, but are still often used to reduce the amount of infiltration from an opening. However, dense-pack cellulose blocks, but does not permanently seal, bypasses, in the way a closed-cell spray foam would. Cementitious foam is applied in a similar manner but does not expand. Spray foam is a type of insulation that is sprayed in place through a gun.
Glass wool and EPS (expandable polystyrene) were by far the most commonly used building insulation materials in 2022, followed by stone wool and rigid foams made of PUR (polyurethane) and PIR (polyisocyanurate). The Building and Construction Authority (BCA) has announced that BIM would be introduced for architectural submission (by 2013), structural and M&E submissions (by 2014) and eventually for plan submissions of all projects with gross floor area of more than 5,000 square meters by 2015. The BCA Academy is training students in BIM. BIM implementation is targeted towards BIM Stage 2 by the year 2020 led by the Construction Industry Development Board (CIDB Malaysia). National Development Plan, 2018 - 2027. Department of Public Expenditure and Reform. The air door is most effective with low exterior wind velocity; at higher wind velocities, the rate of air mixing increases and the outside air portion of the total face flow increases. For commercial applications like store entrances, user comfort dictates lower face velocities, which reduce effectiveness of separation of exterior air from interior air.
For industrial conditions, high face velocities are acceptable, despite noise and buffeting this may cause. Epoxy is too expensive to use as an insulator on its own, but it has a high R-value (7 to 9), high strength, and good chemical and moisture resistance. A HOAT coolant can have a life expectancy as high as 10 years / 180,000 miles. Cold drafts can be avoided by mixing in warm air heated by the air door. Non-heated air curtains are often used in conjunction with cold storage and refrigerated rooms. However, they should not be seen as an alternative to an air curtain, which also functions to separate the indoor and outdoor air spaces. The most common implementation is a downward-facing blower fan mounted over an entrance to a building, or over an opening between two spaces conditioned at different temperatures. Air curtains consume electrical energy during their operation, but can be used for net energy savings by reducing the heat transfer (via mass transfer when air mixes across the threshold) between two spaces. The fan must be powerful enough to generate a jet of air that can reach the floor.
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