Temperature isn't important for most of the buildings. It has strong impact on workers assigned to mining duties. They are far from the city and they work outside buildings. Temperature drops might make them sick. There are two ways to solve this problem.
The first one is placing a steam hub in the working area. This will create a new heated zone - it should reach the mining places. It will increase the temperature in the workplace. It is the best option as it greatly reduces risk of complications.
The second way is securing temperature in the home. By increasing the temperature there, you increase total value of temperature for a citizen. This reduces the risk of illness. On one side this solution is better as it doesn't force you to move the steam hubs from time to time. On other side, this doesn't remove the risk of workers being frozen while working.