Why Is My Home So Dry in the Winter?
The Science Behind Winter Humidity (and What Actually Helps)
Every winter I get the same question from homeowners across Dayton:
“Ben, how can it be 60% or even 80% humidity outside, but my house is bone dry?”
It’s a great question—and the answer has very little to do with your furnace “drying the air out,” and a lot to do with basic physics, building science, and how homes breathe in the winter.
Let’s break it down.
Cold Air, Warm Air, and Relative Humidity (The Key Concept)
Humidity is almost always talked about as relative humidity (RH). That’s the percentage of moisture the air is holding compared to how much it could hold at that temperature.
Cold air physically cannot hold much moisture. Warm air can hold a lot more.
Here’s what happens in winter:
Outside air might be 30°F at 70% RH
That air leaks into your home
You heat it up to 70°F
The amount of moisture stays the same—but the relative humidity drops, often into the 15–25% range
So even though it feels humid outside, once that air is warmed indoors, it becomes extremely dry.
This is why:
Your skin dries out
You get static electricity
Wood floors shrink and crack
You wake up with dry sinuses and sore throats
Your furnace isn’t removing moisture. Heating air simply reveals how little moisture winter air actually contains.
Why Older Homes Are Drier Than Newer Homes
Now let’s layer in some building science.
Older Homes (1940s–1980s)
Many Dayton-area homes fall into this category.
Leaky construction
Poor air sealing
Drafty walls, attics, and basements
High air changes per hour
What does that mean in real life?
Your home is constantly exchanging indoor air with cold, dry outdoor air. Any moisture you add escapes quickly. These homes often need more humidification just to keep up.
Newer Homes (Tighter Construction)
Newer homes are built very differently:
Better air sealing
Higher insulation levels
Controlled ventilation
Lower air leakage
These homes:
Retain moisture much better
Often need less humidification
Can actually have too much humidity if a humidifier is oversized or misused
This is why humidification is not one-size-fits-all. The age, tightness, and ventilation strategy of the home all matter.
What’s a Healthy Indoor Humidity Level in Winter?
For most homes in our climate:
30–35% RH is ideal during colder weather
Above 40% can cause window condensation, mold risk, and wood damage
Below 25% leads to comfort and health complaints
Colder outdoor temperatures = lower safe indoor humidity targets.
A good humidifier setup should modulate output based on outdoor temperature, not just run full blast all winter.
Types of Whole-Home Humidifiers (and Why Installation Matters)
There are several effective ways to add humidity to a home:
Bypass humidifiers
Fan-powered humidifiers
Steam humidifiers
Ductless or space humidifiers (limited use cases)
What matters most is:
Proper sizing
Correct installation
Integration with your HVAC system
Controls that prevent over-humidification
A poorly installed or oversized humidifier can cause more problems than it solves.
The Bottom Line
Winter dryness is not a furnace problem.
It’s not a gas vs electric issue.
It’s not because Ohio is “extra dry.”
It’s the natural result of:
Cold air physics
Air leakage
How your home was built
When humidity is addressed correctly, homeowners often notice:
Better comfort at lower thermostat settings
Less static and dry skin
Fewer respiratory issues
Better sleep
How JBH Heating & Air Can Help
At JBH Heating & Air, we:
Evaluate your home’s construction and air leakage
Measure actual indoor humidity levels
Size and install the right humidifier for your home
Install all types of whole-home humidifiers
Set systems up safely to avoid condensation or moisture damage
If winter dryness is making your home uncomfortable, let’s take a look at it the right way—based on science, not guesswork.
📞 Call: 937-681-5547
🌐 Schedule Online: JBHEnergy.com
— Ben
