Alright, where are my HVAC folks?
We have like 100 y/o steam radiators, and converted from oil to gas last season.
The old boiler (40y) was still working fine, but was rusting out in a spot that made it a ticking time bomb,
so we took the opportunity to convert to gas.
Going in I knew that gas & steam wasn't as good a pairing as oil & steam,
but figured it would be okay.
New system is working well enough, but maybe too well-
With the new boiler we have major humidity issues,
like lack of humidity.
I am not sure what our levels were with the old system,
but now we are getting readings in the 30's
My guess is that because the gas is so efficient, it gets to temp much quicker,
there is no steam output at the radiators.
With the oil boiler, it would take longer to get to temp,
and kind of be a slow burn, and you'd get steam (and humidity) blowing out the relief valves at the radiator.
With the gas, we never hear the whistling we used to from the rads,
I have to believe this is our problem.
Anyone hear of or have this issue with gas/steam system?
Dumped this into one of our future AI overlords as this is what it spit out. I think it's telling you that you're spot on in your assessment, does offer some options:
Your friend's experience is actually pretty common when switching from an old oil-fired steam boiler to a newer gas one—especially with a system that's over 100 years old. The core issue isn't really the fuel type (gas vs. oil) itself, but how the
new boiler's efficiency and behavior interact with an older steam distribution system.
Why You're Seeing Lower Humidity Now
Steam heating systems
don't inherently add meaningful humidity to your home. A properly functioning steam radiator system heats the air without humidifying it—any moisture comes from tiny amounts of steam that might escape through air vents (which is actually a sign of a problem, like clogged vents). The perceived "moist heat" many people associate with old steam systems often comes from
inefficiencies in older boilers: slower heating cycles, wetter steam, and more frequent venting of steam-laden air from radiators.
- Old oil boiler — It likely took longer to reach temperature, produced "wetter" steam (more water droplets mixed in), and ran longer cycles. This caused more steam to escape through radiator vents (that whistling/hissing you remember), adding a bit of moisture to the air. It also drew in more cold, dry infiltration air.
- New gas boiler — Gas burners are cleaner, hotter, and more efficient. The boiler reaches steam temperature faster, produces drier steam, and cycles shorter. This means less (or no) steam escapes from vents, so no extra humidity from leaks. The system is quieter and more sealed, but the air still gets dried out by winter heating (cold outdoor air holds less moisture, and heating it drops relative humidity).
In short: The "humidity" you lost wasn't from the steam heat itself—it was from the old system's quirks. Modern gas steam boilers are designed to minimize those quirks for better efficiency and longevity.
Other Possible Factors
- System tuning — New boilers often need adjustments (e.g., pressure settings, burner tuning) to match older piping. If it's running too efficiently/short cycles, it might not distribute steam evenly, leading to less venting.
- House changes — Any recent insulation, weatherstripping, or reduced air leaks could trap drier indoor air more effectively.
- Winter conditions — Outdoor cold snaps naturally lower indoor humidity regardless of heating type.
What to Do About It
Low humidity (30s %) is common in winter with any heating system, but aim for
40-50% for comfort (less static, better skin/respiratory health). Since steam systems aren't ducted, whole-house humidifiers aren't straightforward, but here are solid options:
- Radiator humidifiers — Place evaporative ones (like Snow Joe or similar metal trays) on top of radiators. The heat evaporates water safely without risking boiler issues.
- Portable humidifiers — Ultrasonic or evaporative models in key rooms (bedrooms/living areas). Clean them regularly to avoid mold.
- Whole-house options — A steam humidifier tied to the boiler (if your setup allows) or a separate electric one. Avoid adding water directly to the boiler—it shortens its life with mineral buildup.
- Other tips — Bowls of water near radiators, houseplants, or hanging wet laundry can help mildly.
Bottom Line
This isn't a "gas vs. steam" problem—it's the efficiency upgrade making the system run "too well" compared to the old one. Your friend isn't alone; many people notice drier air after modernizing. The system is likely working better overall (quieter, more efficient, no whistling vents = good sign of proper venting), but adding a humidifier will restore that cozy feel.
If the humidity is causing real discomfort or issues (cracked wood, static), definitely add some moisture. Otherwise, enjoy the reliable heat—it's a win! If they're worried about the system itself, a quick check by a steam specialist (not just any HVAC guy) could confirm everything's tuned right.