A home hygrometer measures relative humidity (RH%) in the room air. It tells you the general moisture condition but does not measure moisture inside walls, behind furniture or at cold surfaces. Consistent readings over time are more useful than a single number.
Room humidity versus material moisture
A hygrometer (room humidity meter) shows the relative humidity of the air in the room. The EPA mould and moisture guide suggests keeping indoor RH below 60%, ideally between 30% and 50% if possible, to reduce conditions that support mould growth. These are general guidelines, not statutory standards.
A material moisture meter measures moisture within a wall, floor or surface. The reading it produces depends on the instrument type and the material being tested; it is not always a direct percentage of moisture content. A room at 55% RH can still have a damp wall behind furniture where mould grows, because local conditions at cold surfaces differ from the room average.
How to get useful readings
- Place the hygrometer in the room you want to monitor, away from direct aircon output, windows or cooking steam.
- Record readings at consistent times: morning and evening give you a daily range.
- Note the room conditions: aircon on or off, door open or closed, weather (rainy or dry period).
- Try tracking over a week as a practical starting point, rather than treating one reading as a diagnosis.
Sample observation log
Scroll the log sideways on a small screen to see all six columns.
| Date/Time | Room | RH% | Aircon/Dehumidifier | Windows | Observations |
|---|---|---|---|---|---|
As a practical starting point, record consistently over a week. Note morning and evening readings, what equipment was running and whether windows/doors were open or closed.
What the reading can tell you
- Whether the room consistently stays above 60% RH when closed, suggesting conditions that favour mould growth.
- Whether running a dehumidifier or aircon brings humidity down to the target range.
- Whether specific activities (cooking, drying laundry indoors, showering) raise humidity significantly.
What the reading cannot tell you
- Whether a specific wall, ceiling or floor has moisture inside it. That requires a material moisture meter.
- Whether mould is present. Mould can grow at a cold surface even when room-average RH appears moderate.
- The source of moisture: a leak, rising damp, condensation or external seepage.
- Whether a building meets any specific regulatory requirement. General humidity guidance is not a compliance determination for any particular building standard.
Sources: EPA mould and moisture guide. This guide provides general information about home humidity measurement; it does not calibrate instruments or diagnose building defects. Checked 15 October 2026.
Using a Humidity Meter at Home FAQs
What is a good humidity level for a Singapore home?
The EPA recommends below 60% RH, ideally 30% to 50% if possible, as general moisture-control guidance. A room-average reading within that range does not rule out damp surfaces or guarantee that mould cannot grow.
How long should I track readings?
A week of consistent morning and evening readings can be a useful starting point, rather than a mandatory diagnostic period. A single reading does not show how humidity changes with activities, weather and aircon use.
My hygrometer shows 55% but I still have mould. Why?
Room-average RH may be moderate while local conditions at a cold wall, behind furniture or near a window are much higher. A professional moisture assessment checks these surfaces directly.
Do I need a professional moisture meter?
A home hygrometer is useful for room monitoring. If you have recurring mould, visible damp or suspected leaks, a professional moisture assessment can check walls and surfaces directly, providing more specific information about the source than a room reading.