Doors vs No Doors – Refrigerated Supermarket Retail Cases
If you are reading this, you are probably no stranger to the fact that refrigerated retail case manufacturers sell cases both with and without doors. So you might be wondering which you should choose in your store?
Well, like many choices in life, the answer always seems to be, it depends! Frustrating right! Well, here are some of the things that I have come across over the last several years as I’ve become more acquainted with grocery store refrigeration systems.
Energy Efficiency
The logical answer seems to be that a case with doors is more efficient than one without. And when considering the energy usage of the case and the connected refrigeration system, this is true. The table below shows the results of a study that was published in 2010 entitled “Energy Use of Doored and Open Vertical Refrigerated Display Cases” by Brian Fricke and Bryan Becker of the University of Missouri-Kansas City. Here you can see that the net energy usage of an open case compared to a case with doors is 1.3x (2.21 kWh/day/ft vs 1.71). Although this difference is not as large as expected, it is still significant.
However, this study did not take into account the effect that cases with doors have on the overall store conditioning. According to one article I read, about 45% of the heat load imparted on an open case is through infiltration from the ambient space. You can see that open cases actually provide an “air conditioning” effect on the store. So, when the open cases get replaced by cases with doors, the air conditioning load in the store is going to increase. This has to result in an increased cost. I haven’t done a study nor did I find a study by others, but it seems logical to me. Is it enough to offset the energy advantage of cases with doors? I don’t know. I have seen multiple cases where a store replaces or retrofits the majority of their open cases with door cases and ended up short on air conditioning capacity, resulting in humidity and temperature challenges in the store.
Food Quality
Studies have shown that cases with doors do hold a more stable temperature and on average run around 6°F cooler than open cases. These two things result in improved shelf life and overall food quality.
Cold Aisle Syndrome
I am sure that everyone has walked into a grocery store that has open refrigerated cases and noticed the temperature. The overall store is cooler and when you walk down the refrigerated aisle it is almost cold. Especially if you are dressed for a hot summer day outside.
Just this past week, my wife and I visited a grocery store in Massachusetts that had not yet started making the jump to cases with doors. We both noticed, and complained about, how cold it was in the store. Most of the stores in the area where we live have made the change to cases with doors, so they are noticeably warmer.
Impact on Sales
Even today, with high energy costs and societal pressure to “go green” there are still grocery store managers that are hesitant to switch to cases with doors because they are concerned about how it will affect the shopping habits of their customers.
Doors have to be opened if you want to get something out. This takes time. Not a lot, but it adds up. And if you are a shopper who is hoping to get in and out quickly, you may not even have a cart or basket so your hands might be full. Opening a door to grab something or read a label can be troublesome. There is also a chance, and in some cases likelihood, that the doors will have condensation or moisture on them or maybe even advertisements and other signs, making it difficult to see what is in the case.
Some studies have shown that these things can and do affect sales. At the same time, having a nice warm and comfortable aisle to shop in may cause the shopper to linger longer, which can increase sales. So again, the answer is, it depends.
Conclusion
So, in conclusion, IT DEPENDS! There are many factors that you have to consider when deciding which type of case to go with or when deciding if you should make the switch from open cases to cases with doors.
If you are building a new store and you’ve decided to go with doors, your design team will certainly be taking many things into consideration. The refrigeration system will be designed accordingly and so will the building HVAC system.
If you are retrofitting or replacing in a store that was originally designed for open cases, be aware that your refrigeration system will all of a sudden be oversized and the HVAC system will likely be undersized.
Whatever your situation, Carlson & Stewart Refrigeration has probably seen it and can provide insight, advice and assistance. We’ve been designing, building, and servicing refrigeration systems for a long time and would love to help.