Do You Need a Dehumidifier in Winter?

Even during winter, moisture problems can occur in homes and cold spaces such as garages, basements and crawl spaces – although the problems are usually much less severe than in spring, summer and autumn.

This often happens without you even realising it. You ventilate less, add more moisture through showering, cooking, washing, and the weather can change quickly. The result can be condensation, musty odours and microbial growth that creeps up on you.

At the same time, Sweden and Scandinavia cover a large area. What is a clear moisture problem in southern coastal areas may be non-existent during cold periods in the northern inland areas. Therefore, needs vary depending on where and how you live.

When Do You Need a Dehumidifier in Winter?

The need is greatest in cold or semi-heated spaces where moisture remains and where surfaces easily end up below dew points. The exact size of the need depends on the climate, the building, and how the space is used.

Where you live makes a big difference

Northern Sweden and inland areas often have very dry outdoor air during prolonged cold spells. At temperatures around –15 to –25 °C, the absolute low humidity. In heated parts of the house, many people find that the air feels dry as a result.

In cold spaces, moisture problems can still occur, especially in two situations:

• Mild weather and rapid weather changes: as temperatures rise and more humid air enters, condensation can form on cold surfaces.
• Moisture supplied from within: For example, when warm air from the home leaks in, or when snow and sleet melt from the car in the garage.

Southern Sweden and coastal areas often have more humid winter air. There, cold spaces can become damp even without obvious sources of moisture, as the incoming outdoor air already contains more moisture.

Things to consider in the north

Prolonged cold weather can significantly reduce moisture problems. However, this does not mean that a dehumidifier is unnecessary in the north. For many, it serves as a shelter during spring, summer and autumn, when ground moisture and milder weather cause greater stress.

In short: Winter can be a quiet period in parts of northern Sweden, but the need often returns as soon as the temperature rises or rainfall increases unless other measures are taken. During winter, you don't normally need to switch off your dehumidifier - it's mostly on standby and only works when needed.

Spaces Where Dehumidifiers Are Almost Always Very Useful

• Cellar Cold concrete surfaces combined with humid indoor air easily lead to condensation, especially along exterior walls and in corners.
• Garage – often cooler and less well insulated than living areas. Snow, slush and moisture from the car quickly raise the humidity, which can cause rust on tools, soft cardboard boxes and fogged-up windows.
• Crawl space and cold attic – Moisture can remain for a long time. The problems are often greatest from spring to autumn, but even in winter, changes in the weather can cause condensation.
• Storage and ancillary spaces – Low temperatures and limited ventilation mean that moisture, odours and stale air easily linger.

When a Dehumidifier Is Probably Not Needed

• Heated rooms with a stable temperature and functioning ventilation.
• Dry spaces where you see no condensation, smell no odours and measure no elevated humidity.

In heated homes, it is more common for the air to become too dry in winter than too humid.

How to Determine Whether You Need a Dehumidifier

You don't have to guess. Combine measurement with simple observations:

1. Measure the humidity with hygrometer in different weather conditions – not just when everything feels good.
2. Feel and look at surfaces Cold, damp walls or dark spots are clear warning signs.
3. Note smell – musty odour often indicates that moisture never really dries out.
4. Keep an eye out for condensation on windows, pipes, metal and in cold corners.

As a rule of thumb: over 70% RF in cold spaces poses a high risk of odours and microbial growth. Recurring condensation is a clear sign that something is wrong!

📌 Recommended reading: Signs of Moisture Damage and How to Prevent It

How to Run Your Dehumidifier in an Energy-Efficient Way

A dehumidifier does not have to be an energy guzzler:

• Limit air leakage – Open doors and large gaps cause the dehumidifier to work against the outside air.
• Seal where reasonable around ports, valves and penetrations.
• Use energy-saving mode – the dehumidifier operates in a more demand-driven manner and takes several parameters into account before starting. This mode is available, for example, in Acetec EvoDry RCF 20 G1.
• Place correctly – Create circulation where moisture occurs, but avoid blowing directly onto very cold surfaces.

📌 Reading tips: What Does a Dehumidifier Cost?

Signs That You Need a New or Larger Dehumidifier

Sometimes there is already a dehumidifier in place, but it is still unable to keep the humidity down. This can be due to several things, such as the dehumidifier being undersized, worn out or not adapted to the temperature of the space. Signs of this can be that the humidity level does not reach the set value despite long operating time, that condensation continues to occur even when the dehumidifier is running continuously, or that the noise level has increased from, for example, the fan or rotor.

This is often noticeable when odour problems return or electricity consumption increases without any clear explanation.

In cold spaces, the problem may also be the wrong type of dehumidifier. Condensation dehumidifiers often lose capacity at low temperatures, while desiccant dehumidifier are designed to operate effectively in cold environments.

Need Help Choosing the Right Dehumidifier?

To control humidity in garages, basements, storage rooms, cold attics or crawl spaces, correct dimensioning is required. Decisive factors are the size of the space, temperature, air leakage and how the humidity is introduced – for example, via cars, the ground or indoor air.

Acetec AB manufactures desiccant dehumidifiers adapted to the Nordic climate. Please contact us if you would like assistance in selecting a model. or get advice on how to achieve the best possible effect in your particular space.