Yeah, I did a bit of research myself when my bedrock level food storage was spoiling. Turns out that items (torches) adjacent to a door both orthogonal and diagonal count as part of a 'room'. Which means torches placed outside of a room were heating the inside of a room. Apparently even stone floors gave off heat. The inconsistency of cellar temperatures was annoying me so much I went into the game files and set torches and braziers to remove heat when turned off. There now I can make my root cellars properly cold year round.