How many hygrometers does a large house need?

One for each room you are most concerned about is a good start: the main basement space, any wine room, the mechanical room and a closed-up guest suite. Add one in a central upstairs hallway as a reference for the rest of the house.

What if readings are fine but the room still smells musty?

Room air can read normal while a wall cavity, carpet pad or cabinet base stays wet. A musty smell with normal humidity points to a localized source, and moisture readings on the materials themselves are the next step.

Should I share the log with a contractor?

Yes. A few months of readings, especially ones that show spikes after storms or irrigation, help a contractor connect the moisture to its cause and size the problem more accurately.

Indoor Humidity Log for Basements, Wine Rooms and Baths

Sample log layout

Room: Finished basement main room
Reading frequency: Weekly
What to record: Temperature and relative humidity
Note anything unusual: Musty smell, damp carpet edges

Room: Basement storage or mechanical room
Reading frequency: Weekly
What to record: Temperature and relative humidity
Note anything unusual: Water near water heater or sump

Room: Wine room
Reading frequency: Weekly, and after any cooling unit service
What to record: Temperature, humidity and unit setting
Note anything unusual: Condensation on walls or glass

Room: Primary bath or steam shower area
Reading frequency: Weekly, a few hours after use
What to record: Humidity in the adjacent closet
Note anything unusual: Odor or peeling paint

Room: Guest suite or outbuilding
Reading frequency: At each walk-through
What to record: Temperature and humidity
Note anything unusual: Signs the HVAC or dehumidifier is off

Room: Outdoors (reference)
Reading frequency: Same day
What to record: Humidity from a local weather report
Note anything unusual: Storms or long rainy stretches

Copy these columns into a notebook or spreadsheet and record weekly, plus after storms

Reading the trend

IfA basement room stays higher than the rest of the house week after weekThenLook for seepage, a plumbing leak or poor air circulation; consider a dehumidifier while you investigate.
IfHumidity spikes after storms or sprinkler runsThenWater is likely entering from outside; check grading, window wells and downspouts.
IfA wine room climbs above its settingThenHave the cooling unit and its drain inspected.
IfA closet next to a shower reads high after useThenMoisture may be getting through the wall; check the shower's waterproofing and ventilation.
IfAn empty guest suite reads highThenConfirm the HVAC is running and check for an unseen leak.

Getting reliable readings

Use digital hygrometers that show both temperature and humidity.
Place them away from vents, windows and exterior doors.
Compare two meters side by side occasionally; inexpensive units can drift.
Record readings at roughly the same time of day.
Keep the log with the house records so a contractor can see the history.

Common questions

How many hygrometers does a large house need?: One for each room you are most concerned about is a good start: the main basement space, any wine room, the mechanical room and a closed-up guest suite. Add one in a central upstairs hallway as a reference for the rest of the house.
What if readings are fine but the room still smells musty?: Room air can read normal while a wall cavity, carpet pad or cabinet base stays wet. A musty smell with normal humidity points to a localized source, and moisture readings on the materials themselves are the next step.
Should I share the log with a contractor?: Yes. A few months of readings, especially ones that show spikes after storms or irrigation, help a contractor connect the moisture to its cause and size the problem more accurately.

General information for Cherry Hills Village, not a quote or professional advice. In an emergency, call 911.