Any big building is going to experience troubles with heating and cooling at some point.
If a building is older, it is prone to more complications than a newer building might be.
This is the case with the diner I work in. The building is 60 years ancient and 5,000 square feet. The temperature in one section of the building can be seriously unusual in another section at any time. There are many control units that control each unit. In order to keep the heating and cooling system in working order, it is vital that my pal and I keep up with a repair plan. It is usual for an HVAC repair specialist to come in to the diner once a month, then usually, the HVAC specialist will arrive in the morning to check out all of the units for any complications. If they find something that needs to be repaired, they will come back the following morning as not to be in the way during the dinner rush. There have been several instances where the HVAC specialist will find a small problem and then after further investigation, finds out that the problem is much greater and involved. There was one time where the HVAC specialist came in for monthly preventive repair and found a entirely terrible problem. My associate and I had to close the diner for 3 afternoons while the units on the roof were upgraded; Everyone on the staff was really aggravated about this, as they were not able to make currency while the repairs were taking place.