Plenty of homes in Northbrook and Glenview still heat with radiators — cast iron beauties fed by a steam or hot water boiler that has been running, more or less, since the Eisenhower administration. Every winter, owners ask the same question: do I keep fixing this thing, or do I rip it out and go forced air?
There is a real answer, and it is not always “replace.” Here’s how we evaluate radiator heating systems in the north suburbs, what repairs actually cost, and when conversion makes financial sense.
First: Do You Have Steam or Hot Water?
Owners often don’t know, and the distinction changes everything.
Steam (usually pre-1945)
- One pipe going into each radiator, with a small air vent on the side
- A sight glass and low-water cutoff on the boiler
- Banging, hissing, and that unmistakable radiator clank
- Operates near 0–2 psi; no circulator pump
Hot water / hydronic (common 1940s onward)
- Two pipes at each radiator or baseboard
- A circulator pump and expansion tank at the boiler
- Quiet operation, no vents on radiators
- Easy to zone
Steam systems are simpler but less forgiving. Hot water systems are more flexible and are usually the better candidate for keeping and modernizing.
Common Radiator Problems and What They Really Cost
| Symptom | Likely Cause | Typical Repair Cost |
|---|---|---|
| One radiator stays cold (steam) | Failed air vent or pitch problem | $150 – $400 |
| Loud banging / water hammer | Condensate trapped by bad pitch or wet steam | $250 – $900 |
| Cold radiators upstairs (hot water) | Air-bound loop, failed circulator | $225 – $1,200 |
| Boiler short-cycling | Bad aquastat, oversized boiler, control fault | $300 – $1,100 |
| Leaking radiator valve or spud | Packing or valve failure | $275 – $850 |
| Wet base / auto-fill running constantly | Leak in buried return piping | $1,200 – $6,000 |
| Cracked boiler section | End of life | Replace |
Boiler replacement costs (2026, Northbrook & Glenview)
| Equipment | Installed Cost | Notes |
|---|---|---|
| Standard-efficiency steam boiler | $8,500 – $15,000 | ~82–84% AFUE; steam can’t practically condense |
| Cast iron hot water boiler | $7,500 – $13,000 | Durable, simple, ~85% AFUE |
| High-efficiency condensing boiler | $11,000 – $19,000 | 95%+ AFUE; needs low return temps to hit it |
| Add indirect water heater | +$2,500 – $4,800 | Often the best hot water upgrade in a boiler home |
| Add zone valves / new zoning | $900 – $3,500 | Hot water systems only |
The Repair vs. Replace Framework We Use
Four questions, in this order.
1. Is the boiler leaking water from the block itself?
A cracked section on a cast iron boiler is terminal. Sealants buy weeks, not years. If the block is leaking, you’re replacing.
2. How old is it, and is it still in production?
Cast iron boilers commonly run 30–50 years. Past 35, we look hard at parts availability. If controls for your unit are obsolete, a $400 repair becomes a two-week outage.
3. What’s the annual repair spend trend?
Two service calls a winter, three years running, is your answer. The rule of thumb we use: if a single repair exceeds 40% of replacement cost, or cumulative three-year repairs exceed 60%, replace.
4. Are you renovating anyway?
The economics of conversion change completely if walls and ceilings are already open.
Should You Convert to Forced Air?
Honest answer: usually not, unless you want central air conditioning badly enough to pay for it.
A full conversion in a Glenview colonial — removing radiators, abandoning or removing piping, running new supply and return ductwork, installing a furnace and AC — typically runs $22,000 to $45,000. It also costs you space (chases, soffits, a mechanical closet) and, frankly, comfort. Radiator heat is quieter and more even than forced air. Most owners who convert do it for air conditioning, not for heat.
The cheaper path most owners actually take
Keep the boiler for heat, add a ductless or high-velocity system for cooling. In practice:
- Ductless mini-splits: $9,000 – $20,000 for a typical home, and each head can also provide efficient shoulder-season heating
- High-velocity small-duct (Unico/SpacePak style): $18,000 – $32,000, snakes 2″ flexible tubing through existing cavities, preserves plaster and trim
Both leave the radiators in place as your primary winter heat, which in a deep Chicago cold snap is the system you actually want. Our AC installation team quotes both options side by side.
Where a heat pump fits
Adding cold-climate heat pump heads gives you an efficient heat source for most of the season, with the boiler carrying the coldest weeks. That is a dual-fuel strategy in a hydronic house, and it’s the setup we recommend most often to Northbrook owners with solar or high electric baselines. Details on our heat pumps page.
Modernizing a Radiator System You’re Keeping
If you’re staying hydronic, these upgrades deliver the most per dollar:
- Outdoor reset control ($400 – $1,100): Varies water temperature with outdoor conditions. On hot water systems, typical fuel savings of 8–15% and noticeably steadier temperatures.
- Thermostatic radiator valves ($120 – $250 per radiator): Per-room control without rezoning. The single best fix for the overheated bedroom problem.
- Main vent upgrades on steam ($200 – $600 total): Faster, quieter, more even heat-up. Cheapest meaningful improvement on a one-pipe steam system, and the one most often skipped.
- Near-boiler piping correction ($1,200 – $3,000): If the last installer shortcut the header, your steam is wet, your system bangs, and your fuel bill is high. This is the repair that fixes “the new boiler is worse than the old one.”
- Indirect water heater ($2,500 – $4,800): Uses the boiler to make domestic hot water with very high recovery, and lets you retire a separate tank.
- Zoning ($900 – $3,500): Hot water systems only — separate the sleeping floor from the living floor.
Warning Signs You Shouldn’t Wait On
- Auto-fill valve running frequently — you’re feeding fresh oxygenated water into the system and corroding it from inside
- Rust staining or moisture at the boiler base
- Any smell of gas, or soot around the draft hood
- Low-water cutoff that hasn’t been flushed in over a year (steam)
- Radiators cold in one whole section of the house
Frequently Asked Questions
Is my old boiler dangerous?
Age alone isn’t dangerous; poor venting, a failed low-water cutoff, or a cracked heat exchanger are. Annual service, a working CO detector on every level, and a combustion test at the boiler cover the real risks.
Can I remove just one radiator during a remodel?
On hot water, usually yes with proper isolation and re-balancing. On one-pipe steam, removing a radiator changes system pitch and venting — get it evaluated first, or you’ll create a banging problem two rooms away.
Do condensing boilers make sense with cast iron radiators?
Only if the system can run at low return water temperatures — which usually means oversized radiators (common in old homes, actually) plus outdoor reset. If it runs at 180°F all winter, you paid for efficiency you’ll never see.
How long does a boiler replacement take?
Typically 2–3 days for a straight swap; 4–5 if near-boiler piping is being rebuilt or an indirect tank is added.
Will keeping radiators hurt my resale value?
In Northbrook and Glenview, no — buyers care about central air. A home with radiators plus a modern ductless or high-velocity cooling system shows very well.
Get a Straight Assessment
We service, repair, and replace steam and hot water boilers throughout Northbrook, Glenview, and the north suburbs — and we’ll tell you when the right answer is a $300 vent job instead of a $14,000 boiler.
Call (847) 221-6280 or schedule an evaluation. Ask about Sunbit and PowerPay financing on boiler replacements and cooling additions.