Define the period you want to explain
The highest temperature on a room display may occur while nobody is using the room. A useful overheating diary instead begins with an occupied problem: the dining area feels too warm between 17:00 and 19:00, or the spare room remains unpleasant after sunset. State the time window before placing instruments. That keeps the record focused on a decision you can actually make.
Choose one modest question for the first week. You might ask whether closing an existing west blind before direct sun arrives changes the evening pattern. Do not simultaneously compare blinds, fans, window opening and cooking routines. A crowded experiment can produce lots of numbers while leaving the household unable to tell which action mattered.
Use the record to describe conditions and evaluate a reversible comfort change. It cannot certify a building, establish medical safety or prove that a particular energy saving occurred. If conditions are unsafe or local heat advice requires action, use that advice immediately rather than preserving an experiment for a cleaner comparison.
Establish a repeatable measuring position
Put an ordinary room thermometer where it can sample room air without direct sun, contact with a hot surface or a stream from a cooling outlet. Record the height and distance from a recognisable item. The goal is reproducibility, not a claim that this one point represents the entire room. A chair beside warm glass may feel different from the chosen monitoring point.
The Celsius scale shows the quantity to record at each matched-time check. Place your actual room thermometer in a shaded stable position away from direct supply air, hot surfaces and electronics, then describe that location in the log. This close-up does not document suitable placement, a whole-room average or the cause of overheating.
Photo & usage
1-1111 · CC BY-SA 3.0 · Source. Display copies resized and encoded as WebP; no instructional details were fabricated or removed.
If using two instruments, leave them side by side in a shaded stable location before assigning positions. Record any persistent difference after their readings settle according to their instructions. A noticeable mismatch means a tiny later difference between rooms may simply reflect the instruments. This check does not calibrate either thermometer.
Do not move the main sensor to whichever place feels hottest each afternoon. Keep the fixed position and add a separate note about the uncomfortable seat. If you do move it, start a new record segment with the new location. Otherwise a change in measurement position can masquerade as an improvement or deterioration in the room.
Give every reading its context
Set three or four check times around the occupied window. For an evening problem, 16:00, 17:00, 18:00 and 19:00 may be sufficient to reveal the shape. Write the actual reading time, not just the planned slot. Use the same units throughout and avoid adding decimal places beyond the display's resolution.
Alongside room temperature, record sky condition, direct sun on the relevant window, covering position, window and door positions, cooling operation, and unusual activity. An outdoor reading needs a shaded suitable location, or a clearly identified nearby weather source. Do not compare a sun-heated balcony thermometer with a shaded indoor thermometer as though both measured air equally.
Add a short occupant observation using consistent words: comfortable, warm but usable, or stopped using the seat. HSE's thermal comfort material makes clear that air temperature alone is incomplete. Clothing, activity, air movement and nearby radiant surfaces can explain why the same reading accompanies different experiences without making either person's report wrong.
Read an illustrative paired afternoon
These invented observations show how to examine a trial without overstating it. Assume the same sensor position, check times and cooling schedule, with the blind open on Day A and lowered before sun on Day B. Neither day is a controlled laboratory exposure.
| Time | Day A, blind open | Day B, blind lowered |
|---|---|---|
| 17:00 | 29.0 | 28.0 |
| 18:00 | 30.0 | 28.5 |
| 19:00 | 29.5 | 28.5 |
Day A's three-reading mean is 29.5°C: 88.5 divided by three. Day B's mean is approximately 28.3°C: 85.0 divided by three. The difference is approximately 1.2°C after rounding. Those are means of selected readings, not time-weighted daily averages.
If Day B's outdoors was also substantially cooler, the blind's contribution remains uncertain. Record the lower indoor readings as a promising association and repeat on more comparable days. Do not call the calculated difference the blind's certified performance, convert it into an energy percentage, or imply that all seats cooled by precisely that amount.
Choose comparisons that answer the question
A stronger household comparison uses several ordinary afternoons under each setting, with broadly similar weather and activity. Alternate settings when doing so is comfortable and practical; an open-blind trial is unnecessary if it recreates an intolerable condition. Existing notes from ordinary use can provide the baseline instead.
Compare the same times and look at the whole pattern. A lower 17:00 reading followed by the same 19:00 reading suggests a different result from a consistent reduction throughout the occupied period. A lower peak with unchanged complaints may mean the seat's direct sun or air movement still needs attention. Keep those interpretations separate.
YourHome's cooling guidance addresses limiting heat gain, while its orientation material explains why exposure varies with site and time. Use that framework to choose the next change. If temperature rises before any direct sun reaches the window, investigate recorded activity or other exposed surfaces rather than insisting the blind must be the sole cause.
Avoid the most misleading shortcuts
A daily maximum display without a timestamp cannot tell you whether the peak occurred during the problem period. Reset it only if you understand the instrument's memory and record when the reset happened. Otherwise use observed readings with timestamps. A dramatic maximum is less useful than a modest but well-described recurring pattern.
Do not average together readings from different locations or claim precision smaller than instrument uncertainty. Likewise, deleting an unusually hot day because it weakens the result creates a biased record. Mark unusual conditions and analyse them separately, explaining why they differ. Missing readings should remain missing rather than being filled with plausible numbers.
A fan can make a person more comfortable without causing the measured room air temperature to fall. Record its setting and the person's response as a separate outcome. If a curtain adjustment improves glare but leaves temperature unchanged, it may still be worthwhile. Decide against the original complaint instead of forcing every intervention to succeed on one number.
Close the diary with an evidence statement
Write a short conclusion containing the action, observed result, conditions and remaining uncertainty. For example, early blind closure coincided with lower evening readings on three comparable clear days, but cooking differed on one afternoon. Include whether the occupied seat became usable. Such a statement is more defensible than declaring the room fixed after one favourable reading.
Keep the raw log, sensor location description and final operating setting together. Another household member should be able to reproduce the checks without guessing where the thermometer stood. If you cannot reproduce the setting or check time, simplify the routine before collecting another week of data.
Finish when the record supports either keeping the small change or abandoning it for a named reason. Persistent severe discomfort, a large unexplained difference between rooms or a suspected equipment fault can justify professional investigation with the diary as background. The completed household record is a useful description of the problem, not an inspection report or assurance of safety.
THE REFERENCE FILE
Sources & scope
Documentation reviewed 1 Nov 2026. Examples are illustrative; this article does not claim hands-on product testing. Follow the instructions for your actual material, model and location.
