Damp in a closed house: measure it remotely before mould appears
A house near the sea that spends the winter closed, unventilated and unheated, builds up damp: clothes that smell, black patches in the corners, spoilt mattresses. It cannot be seen from abroad. It can be measured.
What humidity is normal
Spain's Regulation on Thermal Installations in Buildings (RITE) sets indoor design conditions of 45 to 60 % relative humidity in summer and 40 to 50 % in winter. If your closed house spends weeks above those figures, mould is only a matter of time.
A sensor that tells you from your home country
A wifi temperature and humidity sensor sends the reading to your phone and alerts you if it crosses a limit. Example: the Shelly Plus H&T, 35.90 € on Shelly's official store. One in the bedroom and another in the coldest room are usually enough to know how the house is doing.
The dehumidifier, and what it uses
A household dehumidifier such as the Orbegozo DH 1655 (16 litres a day) costs 144 € in the shop and, according to the maker's data sheet, uses 230 W. Doing the sum: 8 hours a day is 1.84 kWh, about 40 cents a day at 0.22 €/kWh. For an empty house, the sensible setup is to let it run on its humidistat, only when humidity rises, with the drain hose into a drain so it does not stop when the tank fills.
With a smart plug you can also switch it on or off remotely when the sensor alerts you. We explain it in the connected home guide.
What costs nothing
- Leave interior doors and wardrobes ajar.
- Do not leave damp clothes or towels when closing the house.
- Ask whoever visits the house to open the windows for half an hour on a dry day.
All of this needs the house to stay connected while you are away. If it has no internet, start with «Internet in a holiday home».
Where the figures come from
Prices checked in September 2026. They change: take them as an order of magnitude and always ask for the final price in writing.
Questions about this
Does air conditioning remove damp?
What humidity should trigger the alert?
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