Late October is when the calls stack up in Skokie. The first night in the low 30s hits, a 20-year-old furnace fails to light, and suddenly the homeowner who was casually shopping in September is making a $9,000 decision in a cold house with two hours to think about it. That's how people end up with the wrong size equipment bolted to ductwork nobody measured.
You have a few weeks. Use them. Here's what a real conversation about AC and heating installation in Skokie should sound like, and how to tell when you're getting one.
The checklist: what to nail down before you sign anything
Work through these in order. Most of it is questions you ask, not work you do.
- Get the age and model number off the equipment. DIY, five minutes. The data plate is on the furnace cabinet or the outdoor unit. Most manufacturers encode the build date in the serial number, and a contractor can read it in seconds. Age drives everything else: a 12-year-old furnace with a cracked heat exchanger is a replacement conversation, a 12-year-old furnace with a bad igniter is a $200 repair.
- Apply the repair-versus-replace math out loud. DIY. The common rule of thumb: multiply the repair cost by the age of the unit. If the number clears about $5,000, replacement usually wins. A $600 repair on a 15-year-old system is $9,000 — borderline. A $600 repair on a 6-year-old system is an easy yes. Gas furnaces typically run 15 to 20 years here; air conditioners, 12 to 15, and Chicago's freeze-thaw cycles are hard on outdoor units.
- Ask for a Manual J load calculation, in writing. Pro job, non-negotiable. This is the measurement of what your specific house actually needs — square footage, window area and orientation, insulation, air sealing, ceiling height. If someone quotes you a four-ton unit after walking the perimeter with a tape measure, or because "that's what you have now," you're getting a rule of thumb. Oversizing is the most common self-inflicted wound in this trade. An oversized AC short cycles: it blasts cold, satisfies the thermostat in eight minutes, and shuts off before it ever pulls moisture out of the air. You end up cold and clammy in July and paying more for the privilege.
- Have the ductwork measured, not eyeballed. Pro job. Ask what the static pressure reads. That's the resistance the blower fights against, measured in inches of water column, and most residential systems are designed for about 0.5 IWC. Plenty of Skokie homes measure double that. Leaky and undersized ducts waste 20 to 30 percent of the air you paid to heat, and in the older bungalows and Cape Cods around Oakton and Dempster, the second-floor runs are usually the culprit. New equipment on bad ducts is a new box making the same old complaints.
- Ask whether the return air is adequate. Pro job, but you can spot the symptom yourself. If your upstairs bedrooms run hot in summer and stuffy in winter with the doors closed, you likely have supply without return. Air has to leave the room for more air to come in. Sometimes the fix is a jumper duct or an undercut door, not a bigger condenser.
- Pin down the fuel and equipment type on purpose. DIY decision, pro input. Gas furnaces still make sense for most Skokie houses because January design temps sit near zero and standard air-source heat pumps lose meaningful capacity once it's below freezing. Cold-climate heat pumps have closed a lot of that gap and can work well in a dual-fuel setup with a gas furnace as backup. Ask the contractor to explain why they're recommending one over the other for your house, in plain terms.
- Compare efficiency tiers honestly. DIY. AC efficiency is rated in SEER2 now; furnaces in AFUE. A 96 percent AFUE two-stage furnace runs longer and quieter than an 80 percent single-stage, and in a drafty older home the longer run times even out temperatures between floors. But high-efficiency equipment on undersized ducts underperforms. Spend on the ductwork first. Also check current federal, state, and utility incentives before you buy — the programs change, so confirm what's active the week you're signing.
- Read the quote line by line. DIY. It should name the model numbers, tonnage or BTU input, the new line set or a stated reason for reusing the old one, condensate handling, permit, and disposal of the old unit. Vague quotes protect the seller. A real number for a full furnace-and-AC changeout nationally typically runs $9,000 to $16,000 depending on size, efficiency tier, and how much duct or venting work comes with it; a furnace alone commonly lands in the $4,500 to $8,000 range. Local pricing varies, and anything far below those bands usually means something got left out.
- Get a second opinion when the first one felt like a pitch. DIY. Free second opinions exist for a reason. If the first company's opening move was a replacement quote before anyone measured airflow, a second set of eyes costs you a phone call and can save you five figures.
Two things that are actually urgent this month
Check the burner flame the first time the furnace fires. It should be steady and blue. Yellow, lazy, or flickering flames point to a combustion problem — dirty burners, a cracked heat exchanger, or a blocked flue — and that's a shut-it-down-and-call situation, not a wait-until-spring situation.
Then change the filter and leave the vents alone. One-inch filters need swapping every one to three months, and a four- or five-inch media filter every six to twelve. Skip the highest-MERV thing on the shelf in a one-inch slot; you're choking the blower to chase air quality. And closing registers in the spare bedroom doesn't save money. It raises static pressure and pushes more leakage into your attic and crawlspace.
If you do one thing
Ask for the load calculation. Everything else on this list flows from that number — the tonnage, the duct sizing, the price, whether a heat pump makes sense for your house. A contractor who'll do the math and show it to you is a contractor who plans to install the right equipment. One who won't is guessing with your money, and you'll live with that guess for the next fifteen winters.