The key is that this is not "freezer" but "side-by-side refrigerator-freezer". In theory, at least, a simple freezer left in below freezing conditions will just freeze. Actually, not quite that simple, because a residential freezer ideal temperature is 0 degrees F, not 20 degrees, but if it simply quit working, 20 degrees would keep things safe enough, generally speaking, for a few days.
However, a refrigerator-freezer is a complex device. It typically does not have "a refrigerator temperature" and "a freezer temperature" with mechanisms to keep each compartment at the right temperature (e.g., 38 F refrigerator, 0 F freezer). Instead, it relies on:
- Outside temperature in a very moderate range - typically 50 F (too cold and the refrigerator won't need much cooling...which leads to the freezer getting too warm because nothing is cooling) to 85 F (too hot and the appliance simply can't cool fast enough).
- Both refrigerator and freezer needing cooling at the same time. So if the refrigerator gets warm, the compressor starts running to cool the refrigerator, and the freezer gets cooled down at the same time, and vice versa.
plus, modern refrigerators/freezers are designed to use very little energy. Part of that is handled by insulation - gain less heat and you have to run the compressor less. Part is by minimizing the equipment - if the compressor (and fans and so forth) is smaller/uses less energy when running then the total energy used will be lower.
The end result is that an unconditioned space is bad for a typical "inside" refrigerator/freezer, with bad results to be expected if there are extended times below the nominal refrigerator temperature (the system just doesn't handle it well) or very hot (just can't keep up - and unlike air conditioning where the people can manage and at least appreciate that 80 F inside is a lot better than 100 F outside, a refrigerator that ends up at 50 F will result in spoiled food without you even realizing it!).
The only practical way around the problem is to keep all ordinary refrigerators/freezers in conditioned space. Even in an extended power outage, that is still likely to be better than unconditioned space, at least for the first day or two. (Well, actually in a summer power outage inside is better, in a winter power outage, outside would be better - but that is only the combination of cold + power out. If you have hot + power out or power on (hot or cold) then inside is better.)