Ask what the diagnosis is, what evidence supports it, and what happens if the first repair does not solve the problem. For replacement work, ask for equipment model numbers, capacity, efficiency, sizing method, duct and electrical assumptions, permit responsibility, disposal, warranty, and payment schedule. Ask whether the estimate includes commissioning and a follow-up. Be cautious with quotes that are dramatically cheaper because they omit venting, controls, permits, or labor details. You do not need a long sales presentation. You need a clear scope, a sensible recommendation for the building, and a way to compare like with like. Save the proposal and service records with the equipment manuals.
What to ask next
The right next step depends on the system, the urgency, and the building. Keep the model number, symptoms, age, and any previous service notes nearby when you request an estimate. A professional should explain the diagnosis or sizing basis in plain language.
When to bring in a professional
Use the callback form to describe the issue, or review HVAC services to find the closest starting point. For urgent loss of heat, see what to do in a cold snap.