Attic dehumidifier

There are some unfortunate perceptions that insulation and high ventilation are always a guarantee against moisture problems. This is unfortunately not always true, and especially not when it comes to cold attics.

Those who have added insulation may suddenly discover that moisture problems arise in an attic that was previously problem-free. This is because the temperature in the attic is lowered, and humid indoor air now leaks into the attic where it condenses against the attic's cooled surfaces. To avoid these types of problems, you should ensure that the floor structure is so tight that warm and humid air cannot seep up to the attic from the floors below.

When it comes to increased ventilation in the attic, this can also lead to an increase in moisture problems. Excessive ventilation cools down the attic, which can lead to increased moisture problems when you heat the lower areas of the house.

A good rule of thumb for creating a dry and healthy environment in your house is to consider the interplay between hot and cold. If you can reduce the temperature differences, you can also reduce the risks of moisture problems in the house.

Most of what we cover here primarily concerns unheated attics. It is in the unheated attic that the risk of moisture and mold is greatest.

When you want to use a dehumidifier in the attic, you must take into account the forces of nature and seasonal temperature differences. An unheated attic can get severely cold during spring, autumn, and winter, and you will therefore need a dehumidifier that can operate in low temperatures.

The most common type of attic dehumidifier is the so-called desiccant dehumidifier. They have a clear advantage in that they can also handle cold weather, even sub-zero temperatures.

This type of dehumidifier uses a powerful fan to draw in humid air to a rotor. The rotor is coated with moisture-absorbing desiccants that extract moisture from the air. When the rotor is saturated, warm air flows through it, causing the water to evaporate. The vapor is then discharged from the space via a hose.

The technology is well-proven and familiar to anyone working with dehumidifiers. In other words, you can be sure that you can easily get help if anything should go wrong. However, desiccant dehumidifiers are very reliable.

If you suffer major water damage due to a leaky roof or burst pipes, a desiccant dehumidifier is your best friend. The technology originated in the boat and shipyard industry, so these dehumidifiers are designed to handle large amounts of moisture.

From an energy perspective, it's a good idea to check the energy consumption of the model you are interested in. Modern desiccant dehumidifiers have come a long way in terms of energy efficiency, compared to older models. However, there are still many energy-intensive machines on the market.

A thermal dehumidifier uses heat to induce a thermal movement, where the warm and humid air expands and is thus driven out of the attic space via ventilation.

Thermal dehumidification is relatively energy-efficient, inexpensive to operate, and well-suited for cold spaces.

However, there are some significant drawbacks to thermal dehumidifiers that you should consider before purchasing and especially before installation. An improperly installed thermal dehumidifier can pose a real fire risk. There is also a risk that this type of dehumidifier has a sensor that is not quite able to correctly read the entire attic space. This can then mean that the humidity in the space increases instead, due to incorrect data being fed to the dehumidifier.

Regardless of which dehumidifier you choose for your attic, it's always a good idea to also have at least one standalone hygrometer in the attic. Many dehumidifiers have a built-in sensor with a hygrometer, but they don't always provide an accurate reading for the entire space, which is often large and full of both roof sheathing and trusses.

To get a good understanding of the attic's humidity, you should therefore place a standalone hygrometer in the attic, preferably a good distance from the dehumidifier. It's also a good idea to move the hygrometer around the attic from time to time. This will give you a good idea of the humidity levels in different parts of the attic and also confirm that the dehumidifier is indeed doing a thorough job.

If possible, you should also test the roof sheathing and trusses in the attic with a moisture meter. Measure during spring, summer, and autumn when moisture problems are greatest. Keeping track of the internal moisture of the materials is valuable and allows you to truly understand what's happening beyond what you can see with the naked eye.

It is common for attics in our houses to have problems with moisture. It is a vulnerable spot in the house's construction, where the interplay between heat and cold is more pronounced than anywhere else. Make sure you have a tight roof, good ventilation, and use insulation materials adapted to the specific problems that can arise in an attic.

A dehumidifier in the attic helps to protect your home's attic from moisture and keeps the space dry and fresh. Many of the problems that come with moisture can actually be harmful to both you and your family in the form of mold and rot damage.

With the right dehumidifier and monitoring of humidity levels in your attic, you have every opportunity to get the situation under control and secure your living environment. On Boverket's website, you can read more about house attics and how different moisture problems can arise.