HVAC in Chicago is often a boiler and radiator story sitting inside masonry that lake wind never stops cooling. Steam and hot water systems bang, trap air, and leave one room frozen while the kitchen roasts. Converted bungalows hide ducts in attics that were never part of the plan. Condensers end up in gangways with no room to breathe. Summer humidity then sits in brick that held the day's heat.
A cold radiator beside a hot one is a vent, a trap, or a valve, not a reason to overfire the boiler. If you hear water in a steam main, say so. A boiler that leaks at the sight glass or dumps water on the floor is a different call from a furnace that will not light. Do not mix those symptoms. On windy lake days, a spill at the draft hood gets mentioned first.
Gangway condensers plugged with cottonwood and locked against a fence will not cool a brick top floor. Say whether the outdoor unit is in a gangway, on a roof, or in a yard. If cooling is a window unit in a masonry opening, say so instead of inventing a central system. Filters and closed returns still matter in bungalows. A room over the garage, if you have one, will be the room that fails first.
Have the fuel and the type: steam, hot water, forced air, or something patched together. Say whether you need heat before tonight's wind or whether you are planning before the season. Radiator covers and painted valves belong in the description if a room is cold. A tune, a vent, and a new boiler are not the same ask. If the flue smells wrong, get people to fresh air and lead with that.
Lead with no heat, no cool, a leaking boiler, or a gangway unit that died. Name the floor that is cold while the rest of the building is not. Chicago masonry and lake wind make a failed heater felt the same night. Call the number on this page.