Energy is often a crucial factor when considering new industrial door investments but how often are air curtains in association with non security doors overlooked in favour of fast-acting roller doors, be they PVC, metal or insulated, slatted roller doors? It is estimated that only one in 15 UK warehouses may have installed air curtains and it seems the deterrent factor is the initial cost of the curtain. This dissuading cost factor could be misleading if an in-depth comparison with the various door types’ capital and running costs, mainly the fast-acting roller doors, and a proper assessment of one’s daily door operations have not been done. Each loading bay area, for example, is unique and so that is why each operation needs to be carefully considered.
In supplying a quotation for air curtains a supplier needs to have detailed knowledge of the potential client’s door movements. For example, how big are the doors, and how long are they kept open each day, especially important because some operators have such frequent traffic through them that they tend to keep the doors open for long periods. What are the annual maintenance costs of rapid roll doors, including accident-related costs, and how do their capital costs compare with air curtains? There may also be peripheral costs with rapid roller doors, like infra-red, radio, radar and loops to control door movements. Only when the air curtain supplier has got all this information can it feel reasonably confident in giving an estimated payback on the investment.
Within moments of a rapid door opening internal temperatures can drop by as much as 10 deg C but with an air curtain the difference is normally just 1 deg C. This can mean that with an over-door air curtain energy lost through open doors can be reduced by as much as 80%. Owing to the effectiveness of air curtains in separating internal and external environments, doors can remain open all day with little effect on the heating systems energy consumption and little harm to the internal comfort conditions. A typical door size would cost no more than 30 pence an hour in energy.
When an open door policy is in force owing to traffic flows the problem of pest infestations arises, particularly important for food and pharma applications. In this respect air curtains are not fully effective. On the one hand they can keep out fly infestations, which is why the drinks industry, particularly cider, find them worthwhile. On the other hand they would be useless against rats and birds. However, although more of a nuisance than a pest issue, air curtains offer an effective barrier against smell egress, which is why whey manufacturers favour them.
Air curtains also have hidden benefits. Over-door air curtains induce warm air down from high levels that would otherwise be lost through the roof, so helping to de-stratify the building and eliminate cold spots.
All of the leading door suppliers will supply free energy audits for prospective clients and some of these can be downloaded. Unless users have a handle on such costs, at least in the loading bay, then no really sensible comparisons can be made between the different types of doors and air curtains. Given the impending warehouse energy legislation can any warehouse operator afford to take an insouciant view of this issue?
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