Avoiding Mold in Vacation Homes: Heating Correctly During Absence
The short answer: Mold is often not caused by moisture from outside, but by incorrect heating behavior while saving energy. Leaving your chalet to cool down below 15°C risks condensation on the walls. The solution is a constant base temperature of 16-17°C and intelligent remote control.
In this guide, we show you why "heating off" can be the most expensive decision, how to keep control with smart home technology, and why shock ventilation upon arrival is often too late.
As renovation experts in the Bernese Oberland, we are called to dozens of chalets every spring that "suddenly" smell musty. The problem is almost always the same: The house stood empty for weeks, the heating was on frost protection (5-8°C), and the first warm spring air met ice-cold interior walls. The result: Condensation, the perfect breeding ground for mold.
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Why Cold Walls Are Dangerous
Warm air holds more moisture than cold air. When you arrive at your cold chalet on Friday evening and turn up the heating, the air warms up quickly, but the walls and furniture remain cold for hours (or days).
The warm heating air (and your breath) cools down on the cold surfaces and causes moisture to condense – just like on a cold Coke can in summer. This water penetrates plaster, wood, and textiles. If this happens regularly, mold grows invisibly behind cupboards and wall paneling.
The Golden Rule: 16°C
Many vacation home owners set the heating to 6-10°C to save energy. This is a fallacy.
| Setting | Risk | Heating Cost Effect |
|---|---|---|
| Frost Protection (5-8°C) | High (Condensation very likely) | Low, but expensive reheating needed |
| Eco Mode (10-12°C) | Medium (Risk during weather changes) | Medium |
| Preservation (16-17°C) | Minimal (Walls stay tempered) | Optimal (Little energy needed to heat up) |
At 16-17°C, the walls remain "tempered". The dew point shifts so that condensation becomes much less likely. In addition, you don't have to blast the heat for hours upon arrival to make it cozy.
Smart Heating: Control via App
The most modern solution to this problem is intelligent thermostats. They allow you to control the temperature from Zurich or London.
The benefits for vacation home owners:
- Preheating: Switch the heating to 21°C via app on Thursday. When you arrive on Friday, walls and furniture are already warm.
- Humidity Warning: Good systems (like tado° or Netatmo) also measure humidity and warn you via push notification if it gets too damp.
- Geofencing: The heating notices when no one is in the house anymore and automatically regulates down to the set eco temperature (16°C).
We regularly install such systems as part of our chalet renovations and electrical installations.
Ventilation During Absence?
This is a difficult topic. Tilted windows are a burglary risk and waste energy. Closed windows prevent air exchange.
The best solution for vacation homes is a decentralized living space ventilation with heat recovery. These small devices exchange the air automatically without losing heat. Alternatively: Ask your caretaker or neighbor to air out thoroughly once every 2 weeks (shock ventilation).
Frequently Asked Questions (FAQ)
Is it not enough if I air out for 10 minutes upon arrival?
No. Shock ventilation exchanges the air, but does not warm up the walls. If the walls have cooled down (below 12°C), the fresh air will immediately become damp again as soon as it warms up and hits the wall.
Which smart thermostat do you recommend for underfloor heating?
For water-based underfloor heating, we recommend systems like tado° or Homematic IP. These can learn the thermal inertia of the floor heating and thus control it even more efficiently.
I have already discovered mold. What to do?
Small spots (under 0.5m²) can be removed with methylated spirits. For larger areas or recurring infestation, you must call a professional. The problem often lies deeper (structural defects, thermal bridges), which we can fix during a renovation.
Doesn't heating constantly to 16°C cost extremely much money?
No. Heating a cooled-down house back up to 21°C often consumes more energy than keeping the temperature constant. In addition, with "heating off" you risk expensive damage to pipes (frost) and building structure (mold), which wipes out any heating cost savings.
Does your chalet smell musty or do you want to upgrade to Smart Heating?
We are happy to advise you on the optimal solution for your vacation home.