Log Your Flat Temperature Against What a Landlord Owes
Pick a room, type the hour and the temperature you measured, and the reading lands on a 24 hour chart with the band a Berlin landlord owes at that hour drawn behind it. Everything you log comes back out as a protocol you can paste into an email.
Ranges checked on 9 September 2026 against Berlin tenant-advice guidance and reported rulings. A tenancy agreement can set its own figures, and the night floor is the contested one. This is a record-keeping aid, not legal advice.
When a Berlin flat is cold in October the argument is never about how it feels, it is about numbers at particular hours, and the tenant is the one who has to produce them. Berlin tenant advice is blunt about it: because the tenant carries the burden of proof for underheating, the recommendation is a written record with readings taken several times a day, in the middle of the room, about one metre above the floor. This tool is that record. Pick the room, type the hour and the temperature, and each reading is drawn on a 24 hour chart against the band that applies at that hour: 20 to 22 C in living rooms and kitchens and 23 C in bathrooms between 06:00 and 24:00, and a lower, contested floor overnight. Readings below the line get a red drop showing the shortfall in kelvin, so a week of logging turns into a picture instead of a feeling. Underneath, the same readings come back as a plain protocol grouped by room, ready to paste into the written defect notice that has to come before any question of rent. Every Berlin district runs a free tenant advice service, and a printed log is the thing that makes that appointment useful.
What the chart draws
A full day from 00:00 to 24:00 with the owed band already in place before you log anything. The 06:00 to 24:00 window carries the daytime range for the room you picked. The hours before 06:00 are shaded as the night window with a hatched band, because the night floor is the figure guidance disagrees on: Berlin tenant advice accepts a drop to 16 C, other guidance says 18 C.
How a reading is judged
Each reading is placed at its hour and its temperature. If it sits at or above the floor for that hour it is drawn as a dark dot. If it sits below, a red line drops from the floor to the reading and the shortfall is labelled in kelvin. The counters show how many readings you have, how many are short, and the deepest shortfall, and the note under them separates daytime shortfalls from night ones, because the daytime ones are the stronger half of a case.
Why it produces a text block
A defect notice works better as dated numbers than as a description. The protocol box groups everything you logged by room, in hour order, with the owed figure and the shortfall beside each line, and adds the sentence about where the measurement was taken. Copy it into the email to the landlord, keep the original, and take the same thing to your district tenant advice appointment.
What it cannot do
It does not know what your tenancy agreement says, and a contract can set its own temperatures, although a clause setting figures below the usual daytime range is generally treated as invalid. It does not calculate a rent reduction, because the percentage depends on the whole case and getting that wrong creates an arrears problem. And it cannot vouch for your thermometer: measure in the middle of the room, about a metre up, away from the radiator and the window.