Logging indoor temperature and relative humidity: a placement and reading protocol

Goal

Produce a time series of indoor temperature and relative humidity that can be compared between rooms, days and households, with the reasons for differences visible in the log itself.

Prerequisites

One or more consumer thermometer-hygrometers with a readable display or a data export, a clock, and a fixed place per device. Copy the device's stated resolution (for example 0.1 °C and 1 % RH) from its manual or display into the log header.

Steps

1. Choose one position per device and describe it: room, height above the floor, distance from the nearest window, radiator and exterior wall, and whether sunlight reaches it at any time of day. Do not move the device during the observation window; if it must move, start a new series.
2. Record temperature and relative humidity as a pair, always from the same device, with date, local time and time zone. Read at fixed times (for example 07:00 and 21:00) or export at fixed intervals if the device logs on its own.
3. In a conditions column, note ventilation (window open or closed, for how long), heating or cooling state, cooking, showering, laundry drying, and the number of people in the room.
4. Read relative humidity as tied to temperature. The National Weather Service page on dew point versus humidity states that relative humidity can be misleading, illustrates this with two temperature and dew-point pairs that give 100 % and 50 % RH, and says that the higher the dew point, the greater the amount of moisture in the air. Log RH as displayed, but never compare RH between rooms or days without the temperature next to it.
5. If two devices are used, place them side by side for 24 hours before and after the window and record the difference between them; report it as the inter-device offset.
6. Report: device model and stated resolution, position description, the raw table, the range of each variable, the conditions log and the offset from step 5.

Expected result

A log in which a change in relative humidity can be matched to a change in temperature or to a logged event, and in which two households can see whether positions and devices differ before they compare numbers.

Limits and test basis

Proposed protocol; no target values for comfort, mould or health are stated and none should be inferred from it. Consumer sensors may state no accuracy figure at all; the side-by-side check reveals disagreement between devices, not which device is right. Dew point can be computed from the pair with published formulas, but the log stores only the raw readings.