Air that's too dry in winter is one of the most common complaints in heated Swiss homes: irritated mucous membranes, static shocks, cracking furniture. At the same time, air that's too humid can lead to condensation and mould on cold exterior walls. Both are closely tied to room temperature and the heating system you use. This guide covers the ideal humidity and temperature values by room, how to measure both correctly, and why some heating systems feel "drier" than others.
What is the ideal humidity level in a home?
Relative humidity (RH) measures how much water vapour the air holds at its current temperature relative to the maximum it could hold. For living spaces, 40 to 60% RH is considered ideal, with many building-science bodies recommending a narrower target of 45–55%.
When relative humidity stays persistently below 30%, air is considered too dry: mucous membranes and eyes become irritated, wood furniture and flooring can crack, and static buildup increases. Above 60% — especially on cold surfaces like exterior walls — the risk of condensation and mould growth rises significantly. The Swiss standard SIA 180 ("Thermal and Moisture Protection in Buildings") sets the critical threshold at around 80% relative humidity directly at the surface.
Important: Relative humidity is temperature-dependent. The same absolute amount of water vapour produces a higher relative humidity reading in cooler air than in warmer air. That's why measured humidity often rises in the evening once you turn the heating down.
What is the optimal room temperature by room?
There's no single "correct" room temperature — it varies considerably by how a room is used. These are the values commonly used in Switzerland and the wider German-speaking region:
| Room | Temperature | Humidity |
|---|---|---|
| Living room | 20–21°C | 40–60% |
| Bedroom | 16–18°C | 40–60% |
| Bathroom | 22–23°C | 50–70% (briefly higher while showering) |
| Kitchen | 18–20°C | 40–60% |
| Office / home office | 20–22°C | 40–60% |
| Hallway / rarely used rooms | 15–18°C | 40–60% |
Every degree less of room temperature saves roughly 6% in heating energy as a rule of thumb — one reason zone heating, targeting specific rooms rather than heating an entire home evenly, is increasingly popular.
Does heating fundamentally dry out the air?
Short answer: physically, yes — with every heating system. When air is heated without adding water vapour, its relative humidity drops, because warmer air is capable of holding more water vapour than is actually present. That's pure thermodynamics, and it applies whether you heat with gas, a heat pump, a radiator, or an infrared panel.
The real difference between heating systems lies elsewhere: how much the air itself needs to be heated to feel comfortable.
| Aspect | Convection Heating | Infrared Radiant Heating |
|---|---|---|
| Mechanism | Primarily heats room air | Primarily heats you and surfaces directly |
| Air temperature needed for comfort | Higher | Lower |
| Relative humidity at the same comfort level | Drops more | Drops less |
| Air circulation / dust disturbance | Higher (especially fan heaters) | Lower |
Because an infrared panel radiates heat directly onto you and the surfaces around you, you feel comfortable at a lower air temperature than in front of a radiator. Since less air-heating is needed to reach the same sense of warmth, the resulting humidity drop is typically smaller than with a classic convection heater, which has to raise the air temperature itself to produce the same felt warmth. On top of that, without a fan — and without hot radiator surfaces scorching dust — less dust gets stirred into circulation, an effect also reflected in the Fraunhofer WKI air-quality measurement on the SunWave Ceramica (0.043 mg/m³ total VOC, far below the 10 mg/m³ limit, no carcinogenic compounds detected).
To be honest: No heating system actually "humidifies" the air. The real advantage of radiant systems is producing comfort at a lower air temperature — not adding moisture. If air stays persistently dry, only humidification or proper ventilation helps, regardless of heating type.
How to measure humidity correctly
A simple hygrometer (from around CHF 15–20 at any hardware store) is entirely sufficient for home use. For reliable readings:
- Placement: At roughly seated head height (~1.5 m), not directly above a heat source, not in direct sunlight, and not right next to a window.
- Measure several rooms: Bathrooms and kitchens naturally run higher due to showering and cooking than bedrooms do.
- Observe over days: A single reading tells you little — humidity fluctuates throughout the day with heating behaviour, cooking, showering and ventilation.
What to do about dry air in winter
Before reaching for an electric humidifier, these device-free measures are worth trying first:
- Houseplants: Continuously release moisture through their leaves.
- Bowls of water: Placed on a windowsill or near a heat source, water evaporates slowly into the room.
- Dry laundry indoors: Instead of in a tumble dryer — a classic, effective moisture source.
- After showering: Leave the bathroom door open instead of ventilating immediately, letting moisture spread through the home.
- Ventilate correctly: Burst ventilation rather than tilting windows continuously (see below).
Only once these measures aren't enough, and humidity stays persistently below 30%, does a humidifier with hygrostat control become worthwhile.
Ventilating correctly in winter: burst ventilation, not tilted windows
Windows left tilted open continuously cool the window reveal significantly, raising the local condensation risk there — exactly the combination of a cold surface and humid air that encourages mould. Burst ventilation is better: open windows fully for 5–10 minutes several times a day, ideally with a cross-draft. This fully exchanges the room air without permanently cooling walls and furniture. For more on the link between ventilation, cold surfaces and mould risk, see Infrared Heating and Mould Prevention: What Actually Helps?
Note: The values in this article are general guidelines for healthy adults in normally used living spaces. If you have respiratory conditions, allergies, or rooms with special requirements (e.g. musical instruments, sensitive furniture), different target values may be appropriate — consult a specialist if in doubt.
Frequently Asked Questions
What is the ideal humidity level in a home?
The ideal relative humidity in living spaces is between 40 and 60%, with many building-science bodies recommending a narrower target of 45–55%. Below 30%, air is considered too dry (irritated mucous membranes, static buildup); above 60%, especially on cold surfaces such as exterior walls, condensation and mould risk rise significantly.
What is the optimal room temperature for a bedroom?
Sleep specialists generally recommend 16–18°C for bedrooms — cooler than living rooms or bathrooms. Overly warm bedrooms often disrupt sleep, while overly cold ones combined with high humidity encourage condensation on exterior walls.
Does heating fundamentally dry out indoor air?
Physically, yes — relative humidity drops whenever air is heated, regardless of the heating system. That's basic thermodynamics, not a property of any particular heating type. The real difference between systems is how much the air itself needs to be heated to feel comfortable: the less air-heating required, the smaller the humidity drop.
Why does the air often feel less dry with infrared heating than with radiators?
Infrared panels warm you and surfaces directly through radiation, rather than primarily heating the room air. That means a room feels comfortable at a lower air temperature. Because less air-heating is needed to achieve the same sense of warmth, relative humidity drops less than with a convection heater. On top of that, without a fan, less dust gets stirred into circulation — an effect also reflected in the Fraunhofer WKI air-quality measurement on the SunWave Ceramica.
How can I raise humidity in winter without buying a humidifier?
Effective device-free measures: houseplants, open bowls of water on radiators or windowsills, drying laundry indoors instead of in a tumble dryer, and leaving the bathroom door open after showering instead of ventilating immediately. Only reach for a humidifier if these measures aren't enough and humidity stays persistently below 30%.
How often and how long should I ventilate in winter?
The recommended approach is burst ventilation: open windows fully for 5–10 minutes several times a day rather than leaving them tilted open continuously. This fully exchanges the air without permanently cooling walls and furniture — windows left tilted open, by contrast, cool the window reveal and raise the local condensation risk there.
Comfort at a Lower Air Temperature
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