Replacing an HVAC system is one of the larger home investments a Pittsburgh homeowner will make. Done right, a new system delivers 15–20 years of reliable comfort. Done poorly — wrong size, wrong equipment, poor installation — it can mean years of callbacks, high energy bills, and premature failure. This guide covers the decisions that matter most.

When to replace rather than repair

The general guidance is to replace when repair costs exceed 50% of the replacement cost, or when the system is more than 15 years old and experiencing significant problems. But the real calculation is more nuanced: a 20-year-old furnace that needs a $400 repair may still be worth fixing if it is otherwise running well. A 12-year-old system with a failed compressor and a history of problems may be better replaced. An honest technician will help you think through the math.

Sizing: the most important decision

Equipment sizing is determined by a load calculation — an assessment of the home's actual heating and cooling needs based on insulation, windows, air leakage, square footage, ceiling height, and local climate data. The ACCA Manual J is the industry standard method. A contractor who sizes equipment based on square footage alone, or by matching the existing unit's capacity, is skipping a step that matters.

Equipment selection

For most Pittsburgh-area homes, a high-efficiency gas furnace (90%+ AFUE) paired with a central air conditioner or heat pump is the standard replacement path. Heat pumps have become increasingly viable in western Pennsylvania as cold-climate models have improved — they can provide efficient heating down to low outdoor temperatures and may qualify for federal tax credits. The right choice depends on your home, your existing infrastructure, and your priorities.

Vetting a contractor

Ask any contractor you are considering: Do you perform a load calculation before recommending equipment? Are you licensed and insured? Do you pull permits where required? What does your startup commissioning process include? A contractor who cannot answer these questions clearly is a contractor to avoid.

Heirloom Mechanical installs and replaces HVAC systems throughout Allegheny, Westmoreland, Fayette, and Washington counties. We carry PA HIC No. PA196206, are fully insured, and perform load calculations on every replacement project. Call 412-889-6800 for a free in-home estimate.