Heating
Installing a new furnace, sized correctly for the home, when repair no longer makes sense.
A furnace nearing or past its typical service life, or one that's needed repeat repairs, is usually a candidate for replacement rather than continued patching — newer systems also tend to be meaningfully more efficient.
Related
Diagnosing and fixing a system that's blowing warm, cycling oddly, or has stopped cooling altogether.
Sizing and installing a new central air system, or replacing one that's past the point of repair.
Getting a furnace, boiler, or heat pump that's underperforming — or out entirely — back to reliable heat.