The science of secondary doors


09 October 2017
Kenfield Doors Managing Director Tom Moloney explains how energy-saving doors can make a big difference to efficiencies in supermarkets and in food processing.

Insulated energy-saving secondary doors can play a key role in increasing margins in the food processing and the supermarket sectors. With money tight and end users looking for high-end savings, storing products in an energy-efficient environment will make a considerable difference to the bottom line of any supermarket or food processing operation.
It is hard to believe that in some cold stores and freezers, doors are left open to allow ease of movement for staff. These can be heavy, ill-fitting and a hazard to employees. This leads to cooling systems having to work harder and results in increased energy costs which are ultimately passed on to the customer.

Kenfield has been working on a new generation of insulated, flexible, energy-efficient secondary doors over many years. In 2013 we began trialling the Kenfield K750 Insulated Energy Door with Sainsbury’s and Tesco and the results were impressive with proven savings in energy costs, workplace efficiencies, ease of use, maintenance and longer life.

Optimum level
Our uniquely designed and patented K750 door was launched that year and since then thousands have been fitted in cold stores, chillers and freezers across the UK with other supermarket majors including Asda, Morrisons, Marks & Spencer and Aldi joining our list of customers.

Often when building a cold store or freezer the main cooling system is at the forefront of the mind of the refrigeration installer or designer. But secondary doors can make a big difference to the overall energy bill and working environment and they should be included as part of the plans from the start.

Without secondary doors, the outer doors are vulnerable and poor maintenance, and the fact that they are heavy and awkward to slide, will lead to employees leaving them open.

But the outer door can stay open if secondary doors are fitted. These light, PVC covered doors – with no sharp surfaces – can be pushed through with ease by staff.  They will automatically close behind them, won’t hurt them if they brush through and will ensure that the temperature inside the freezer or cold store is maintained at an optimum level.

Prevent snowing
Fitting secondary doors also saves a lot of time in the working environment as staff will not have to open and close the outer doors when they pass through what could be hundreds of times a day. The knock-on effect is that it will take fewer people or less time to unload a lorry or restock the shelves.

Outer doors also have alarm systems to monitor their use remotely and these alert the management when they are left open. Once secondary doors have been fitted and the temperature inside the cool area is maintained at a constant level, the alarms will sound on a less frequent basis.

Secondary doors can also help prevent snowing. This occurs when you get a build-up of warm air in a cold room which leads to condensation on the ceiling which then drops down as snow. In turn this can lead to icing on the floor which can cause accidents for staff and can be particularly dangerous if heavy trolleys are being employed.

Flexible panels on our energy efficient secondary doors mean that they are versatile enough to bend around corners and this lightness and ease of use gives them the edge in the cooling environment over other alternatives. Secondary doors don’t tangle or attach themselves to passing trolleys containing foodstuffs. The K750 has two layers of insulation – with an air gap in between – which places it in a different league when it comes to keeping the cool air in and the warm air out.

Low maintenance
Secondary doors have to be robust as they are in constant use. Traffic to and from the chiller or freezer in a major supermarket or warehouse can be heavy with people and trolleys passing through at a rapid rate. Knocks and bangs are a normal part of this so the doors have to be built of materials that can withstand this wear and tear. Our doors are manufactured to withstand this and have very low maintenance.

Health and safety is another important issue to consider. A door propped open can present all sorts of trip hazards and no employer wants to have to explain to the Health & Safety Executive why a door was at fault at the time of an accident. With food the main product in a cold room or freezer, hygiene is a key factor to consider. Easy to maintain wipe-clean secondary doors ensure the perfect environment for foodstuffs to pass through. 

Staff are also often worried about being stuck behind a heavy door or locked inside a cold room or freezer but because secondary doors are light and easy to use this removes any of these anxieties.

Secondary doors pay for themselves very quickly. I can recall one occasion when we tested a door it was found to be 16°C on the outside of the room and -22°C on the inside where the food was stored. Customers have reported savings in the region of 20 to 25% on their energy bills and in this respect the figures speak for themselves. Away from the UK, customers in Europe also like what we do and I believe that the future is bright for secondary doors in the cooling industry.
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