What size furnace does my Chicago home need?

Chicago's 99% heating design temperature is -8°F (ASHRAE Fundamentals — meaning temperatures reach -8°F or lower on the coldest 1% of hours). January wind chills in Chicago regularly drop to -20°F to -30°F. For this climate, ACCA recommends 96% AFUE furnaces at minimum efficiency. Furnace sizing requires an ACCA Manual J load calculation specific to your home — square footage, insulation levels, window area, and building orientation all affect the correct BTU capacity. Do not accept an equipment recommendation that is simply "same size as what was there" without a load calculation.

Do I need a permit to replace my HVAC system in Chicago?

Yes. The Chicago Department of Buildings requires a permit for any HVAC equipment replacement — furnace, central air conditioner, heat pump, or boiler. Licensed HVAC contractors can pull most residential replacement permits through the [Chicago DOB Express Permit Program](https://www.chicago.gov/city/en/depts/bldgs/provdrs/permits/svcs/express-permits.html) online, often the same day. Permit fees run approximately $175–$450 for standard residential HVAC replacements. Work performed without required permits constitutes a code violation and may affect homeowner's insurance coverage.

What rebates are available for HVAC upgrades in Chicago in 2025?

Multiple programs apply: - People's Gas / North Shore Gas: $300–$1,200 for 96%+ AFUE furnace installations (rebate applied at time of service) - ComEd: Up to $600 on qualifying cold-climate heat pumps; $75–$100 on qualifying smart thermostats - Federal IRA 25C Tax Credit: Up to $2,000 for qualifying cold-climate heat pump systems; up to $600 for qualifying furnaces

How long should my HVAC system last in Chicago?

Chicago's demanding climate shortens HVAC equipment lifespans compared to milder markets. Typical Chicago ranges: gas furnaces 18–22 years (vs. 20–25 nationally), central air conditioners 12–16 years (vs. 15–20), cold-climate heat pumps 14–18 years. High-efficiency equipment maintained with annual professional tune-ups (furnace in October, AC in April) reaches the upper end of these ranges. Postponed maintenance significantly compresses lifespan in Chicago's operational extremes.

What is a cracked heat exchanger, and why is it dangerous?

The heat exchanger is the component inside your furnace that separates combustion gases from the air circulating through your home. A crack allows combustion byproducts — including carbon monoxide (CO), a colorless, odorless toxic gas — to mix with living space air. Cracked heat exchangers are caused by thermal stress and are accelerated by: oversized equipment (rapid cycling), restricted airflow (dirty filters), and age. Illinois law (210 ILCS 74) requires working CO detectors within 15 feet of sleeping areas in all homes with gas-burning appliances. If an HVAC technician identifies a cracked heat exchanger, the furnace must be replaced — this is not a negotiable repair.

Why does my boiler have pressure issues in my Chicago two-flat?

Chicago two-flat, three-flat, and greystone buildings with hydronic (hot water or steam) systems frequently develop pressure issues from: air trapped in radiators (bleed them seasonally), waterlogged expansion tanks (replace the diaphragm tank), or failing pressure relief valves (replace every 10–15 years). These are maintenance items, not replacement triggers — a qualified Chicago plumber or HVAC technician familiar with older hydronic systems (a specific skill set; not all HVAC companies service steam systems) can typically resolve pressure issues for $150–$600. Chicago steam boiler specialists are found predominantly in older North Side and South Side neighborhoods where this building stock concentrates.

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