Key points
- The EPA suggests keeping indoor humidity below 60%, ideally between 30% and 50%.
- Utah air is dry most of the year, but basements and bathrooms can still run damp.
- In winter, high indoor humidity shows up as window condensation and attic frost.
- A cheap hygrometer tells you where you stand.
Why it matters
Mold needs moisture. Keeping humidity in range makes it much harder for mold to start on walls, windows, closets and stored items. The EPA suggests keeping indoor humidity below 60%, ideally between 30% and 50%.
Basements
Basements stay cool, so the air near walls and floors can be much damper than upstairs, especially in summer. A musty smell is a sign — see musty smell in the house. A dehumidifier set correctly helps — see dehumidifier settings for basements and mold in the basement.
Winter
Outdoor air is dry, but cooking, showers and furnace humidifiers add moisture inside. When it meets cold glass or a cold roof deck, it condenses:
- Water and mold on window sills — see window condensation mold.
- Frost and drips in the attic — see attic frost and condensation.
- Leaks from a furnace humidifier — see furnace humidifier leak.
Simple steps
- Use a hygrometer in the basement and main floor.
- Run bathroom fans during and after showers; make sure they vent outside.
- Turn a furnace humidifier down when windows fog up.
- Fix leaks quickly — a slow leak keeps one spot damp no matter what the room reads.
Found mold anyway? See mold remediation in Provo or our mold inspection pricing.
Common questions
What humidity should I aim for in winter?
Lower than in summer when it is very cold outside, because moist air condenses on cold windows and roof decks. If windows fog or frost on the inside, turn the humidifier down.
Can the air be too dry?
Yes. Very dry air can cause static, dry skin and gaps in wood floors. The goal is a balance: enough humidity to be comfortable, but not so much that condensation forms.
Are cheap hygrometers accurate?
Inexpensive ones can be off by a few points. That is fine for spotting trends — whether the basement is much damper than upstairs, or humidity jumps after showers.
Musty basement or foggy windows?
Call (385) 250-2825 — answered live 24/7 by the Vault crew.
Mold remediation in Provo · Mold inspection pricing · Contact us