The debate around whether to make it mandatory to have doors on all display refrigerators in the U.K. has been reignited by a combination of carbon targets and public pressure.

While supermarkets in the U.K. have historically been resistant to adding doors to fridges because of fears that they will impact purchasing, the mounting pressure on the U.K. to reduce energy to meet long-term carbon targets has put the subject back on the agenda. In the U.K., although freezer cabinets have now moved away from open designs to be almost universally offered with doors or sliding lids, many merchandisers cling to the belief that the addition of doors to their chiller cabinets will negatively affect the purchase of goods by presenting a “barrier” to browsing.

But the doors on fridges debate has gathered new momentum in the wake of the U.K. signing up to “net zero” carbon emissions by 2050. Fitting doors is reckoned to provide energy savings of at least 30% over open cabinets.

A review of research in a 2014 Institute of Refrigeration paper reported a range of savings starting at 25% and ending on a massive 86%. Putting doors on fridges is thus seen as low hanging fruit in the search for carbon reductions.

Further weight has been added by a petition from a member of the public to the U.K. Parliament’s online petition site calling for it to be made a legal requirement to put doors on open cabinets.

The petition from Jonathan Golding, a Brighton doctor, passed the 20,000-signature mark, which triggers a response from the government. It is currently on 29,000 signatures.

In the petition, titled "Ban energy-wasting open fridges and freezers in all retail outlets," Golding said: “Retailers in the United Kingdom unnecessarily waste huge amounts of energy on open fridges and freezers. Climate change threatens our planet. If all supermarkets had doors on their fridges and freezers it would save energy the equivalent of the entire residential population of Poland.”

However, the response from government department Business, Energy and Industrial Strategy (BEIS) has been distinctly cool: The department said that it was not prepared to intervene not intervene, because the European Ecodesign energy regulations are nonprescriptive in terms of technology.

BEIS said: “Minimum energy performance standards, otherwise known as Ecodesign regulations, are technology neutral so do not prescribe that manufacturers should increase efficiency by putting doors on appliances.

Rather they set a minimum energy efficiency limit that all manufacturers placing products on the market must meet. The legislation therefore leaves it up to the manufacturer as to how they meet the requirements, which could include but is not restricted to putting doors on fridges.”

However, the argument runs, if all the supermarkets were to agree to fit doors, any concerns about footfall would cease to be an issue, because it is the same for everyone, and the net result would be energy savings across the board.

France has put this theory into practice with a voluntary agreement amongst its retailers that has the goal of putting put doors on 75% of its chiller cabinets nationwide by 2020. This move alone is reckoned to be able to save a massive 1% of the French national electricity bill.

But such a move has so far been resisted in the U.K. — partly because the cost equation for elements such as maintenance is hard to justify. One supermarket refrigeration manager said: “For bigger stores, the debate is ongoing…In a new store, doors stack up, because you can downsize the refrigeration plant accordingly; but for retrofitting existing stores, the payback is currently something like 15-21 years because of all the alterations needed – and that’s before all the additional maintenance and cleaning of the doors, the heating adjustments and the like.”

Retailers have acknowledged that open chiller cabinets present a dual problem — they waste energy and they make the aisles colder, risking discomfort for the shoppers — so a number of supermarkets have adopted energy-reduction measures specifically designed for open cabinets.

The most widely adopted of these have been aerofoil strips for the ends of shelves, which redirects the air to stop it spilling out into the aisles. These simple strips have been developed in collaboration with motor racing engineering teams to reduce turbulence in the multi-deck air curtain.

However, there are also now several new technologies which offer a whole-cabinet approach — the manufacturers of such technologies claim that the cabinet energy savings are now approaching those of installing doors.

The “adapt the open cabinet approach” has been given further weight by an open-deck specialist, who has warned that the number of door openings per hour in real store trials far exceed the number used in energy calculations for enclosed cabinet.

AD&E said that the industry standard for the testing of refrigerated retail display cabinets, BS EN ISO 23953, is based on 10 door openings per hour with an opening/closing cycle of 15 seconds, but real-store openings are nearer 60 per hour in larger supermarkets.

The firm also found in its own laboratory tests that average test pack temperature rose by 5 degrees C due to the door openings. Significantly, the increased temperature in the cabinet increased the duty on the refrigeration plant with a consequent surge in energy consumption.

The AD&E managing director said: “Our tests clearly demonstrate that glass doors cabinets, designed for 10 openings per hour, experience significant loss of temperature control at an opening frequency of 30 openings per hour or more.”

So, while the argument for doors on fridges may look compelling, in the U.K. at least, it is anything but an open-and-shut case. Should such a move be made mandatory? That is very much an ongoing debate.