Comment: Top tips for air curtain success

Air curtains save energy and increase comfort by minimising the amount of cold air entering a building while keeping the warm air inside – but only if they are designed, sized and installed correctly. Here ANDREW SAXON, marketing manager at Biddle Air Systems, provides five top tips to ensure a successful outcome

1. Never treat an air curtain as a space heater

An air curtain isn’t designed to heat a room; its job is to create a barrier that minimises the amount of cold air entering the building while keeping warm air inside

While there are over-door heaters available on the market, which are usually small and positioned in the centre of a door, an air curtain shouldn’t be used as the primary heat source for a space.

An air curtain isn’t designed to heat a room; its job is to create a barrier that minimises the amount of cold air entering the building while keeping warm air inside. Though an air curtain’s air stream is warm, unless it’s an ambient/no heat model, and thus can contribute to the heating around an entrance, it will actually work alongside a building’s heating system, rather than replacing it.

2. Make sure the air curtain is installed in the correct position, and it’s the right size

For an air curtain to work effectively it must be correctly sized and installed. The effect a poorly-designed, selected or installed air curtain has on energy consumption can actually be worse than not having an air curtain installed at all.

Air curtains should be fitted horizontally over a door, or, if necessary, mounted vertically to the side. They must be installed inside the doorway as close to the opening as possible and must be just wider than the opening with an overlap at both sides, or at the top if it is a vertical installation.

It’s important to note that air curtains should be specified on the size of the door, not the kW output. Air curtains are generally available in 1m, 1.5m and 2m lengths and can be seamlessly joined together if required.

3. Get the air stream right

The effect a poorly-designed, selected or installed air curtain has on energy consumption can actually be worse than not having an air curtain installed at all

The design of the air curtain must be suitable to discharge air across the whole height and width of the opening, at a suitable supply air temperature and velocity, and the heat output of the air curtain must be sufficient to temper the volume of air coming in at the entrance.

The characteristics of the building and the outdoor and indoor climate conditions must also be considered, as well as the power requirements. It is really important to spend time getting the jet stream right; it won’t be effective if it has too little velocity or is too powerful. An engineering design procedure for calculating the supply air flow and thermal capacity of an air curtain is explained in the BSRIA Application Guide 2/97, Air Curtains – Commercial Applications . Manufacturers should also be able to provide assistance, and illustrative CFD graphics.

4. The more efficient the heat source, the more efficient the installation

An air curtain’s warm air can be derived from various sources, including direct electric heating and low, medium or high pressure hot water. Modern air curtains are designed to operate with 60/40 condensing boilers and heat pumps – increasing their efficiency – so these should be utilised if possible.

In conventional installations energy wastage can be cut by up to 80%, drastically reducing energy bills and carbon emissions, but combining an air curtain with a condensing boiler or a heat pump can deliver even greater savings.

5. Use controls to increase efficiency

Controls are essential in preventing unnecessary energy usage, and are a major area of focus for the air curtain market.

A typical air curtain will have a manual control, set up at the time of installation. Although the end user can change the settings for the flow and temperature of the air stream, in our experience it’s unlikely this happens.

Furthermore, environmental conditions are constantly changing, so the settings will only be right some of the time, and wrong a lot of the time – wasting energy and money.

Automatic controls are now being widely introduced, which react to indoor and outdoor temperatures. This means air curtains will be able to operate at an optimum setting all of the time, increasing energy efficiency.