Why are some rooms in my house too hot or too cold?

Uneven temperatures are usually caused by duct leakage, improper duct sizing from the original install, or dampers that need adjustment. Older homes often have duct systems that were sized for equipment that's no longer installed.

Other causes include poor insulation in specific areas or a single-stage system that can't modulate output. A zoning system or a variable-speed unit can often solve chronic comfort issues that duct sealing alone won't fix.