How cold below freezing and for how long? Couple of spots to think of is your bypass valves for your water heater. There can be a few inches of water above one of the valves; I would ensure all three valves are fully open. Also check your water pump, there is a screen filter basket, depending on how it is configured it can hold water and potentially freeze and break the clear cup. I have had that happen
. Beyond all your pipes and facets, do not forget the drain traps. They are hard to drain of water, because of it I do pour a bit of antifreeze down the drains.
If you are concerned about potential damage a small electric heater running on low in the unit with the cabinet doors open could help.