09/05/2026
I hear this one all the time...
“My humidity is under 50%, so I shouldn’t have mold…right?”
Not necessarily.
Keeping the humidity in your home around 50% or below is a good idea. We recommend it. But 50% isn’t some magic number where mold suddenly can’t grow.
The humidity reading on your thermostat is only telling you what’s happening in that particular area at that particular time.
What really matters is what’s happening at the surfaces and building materials.
A room might be at 48% humidity, but what’s happening behind the couch against a cold exterior wall? Under the flooring? Inside a closet with very little air movement? Around an HVAC register? In a wall cavity where outside air is getting in?
Those conditions can be very different.
Surface temperature matters. Air movement matters. The temperature of the building materials matters. Air infiltration matters. Insulation matters. HVAC run time matters. An oversized system that short cycles can cool a house without doing a great job of removing moisture.
And a temporary humidity spike above 50% doesn’t automatically mean you’re going to have mold either.
It’s about the combination of moisture, temperature, time, airflow and the actual conditions of the materials.
So yes.. keeping your home around 50% RH or below is a good practice.
Just don’t make the mistake of thinking that number alone tells you whether you have a mold problem.
Humidity is a data point, not a diagnosis.
