Do you open the attic and encounter a trapped, musty or earthy odour? Do you see discoloured spots everywhere? You are not alone. Bad odours from the attic are a common problem - especially in older houses and cold attics with poor air circulation and moisture management - and often a sign that something is not right.
In many cases, this is due to excessive humidity, poor ventilation and mould growth. Here we look at what causes odours in the attic, how to check the moisture situation and a remedy that works quickly and effectively.
The odour that arises in an attic can be caused by several things, but at its core it is almost always a combination of moisture and poor air circulation. The attic is often a cold and poorly ventilated space into which warm, moist air from the home rises through leaks or insufficient insulation.
The result is a confined environment with condensation that can lead to microbial fouling - and, over time, a distinct odour that spreads throughout the home.
Odours from the attic are often a symptom of what could be - or develop into - a bigger problem. When humidity levels are too high for a long time, there is a risk of mould spores taking hold, which in turn can have a negative impact on both indoor air quality and the structure of the house.
Some people are sensitive to mould and may experience symptoms such as respiratory irritation or allergies, but the impact on the individual varies. If you suspect a health impact, you should always contact your healthcare professional for advice.
If the smell is distinct and recurring, don't wait - the risk is that the problems will get worse over time, especially during autumn and winter when the temperature differences between indoors and outdoors are greatest.
The first step is to go up to the attic and inspect with both your nose and eyes. Check for a musty or earthy smell, and look for visible signs of damp or mould on wood, plastic sheeting or insulation. Are there drops of moisture? Discolouration? Does the insulation feel damp? Also check for leaks in the roof.
Then measure the relative humidity (RH) with a hygrometer - or hire a moisture expert if you want to be absolutely sure. An RH above about 75% for a long time means a high risk of mould growth.
📌 Reading tips: Signs of moisture damage
The key to getting rid of odour problems is to create a stable and reasonably dry climate in the attic. You can do this by improving ventilation, but ventilation flow is difficult to fully control as it is affected by things like weather, temperature, insulation and pressure differences. A dehumidifier, on the other hand, quickly provides an effective solution that gives you concrete and reliable control over humidity.
If you already have mould growth in your attic you must start by sanitising before installing a dehumidifier. Once the decontamination is complete, a dehumidifier can used for preventive purposes to reduce the risk of the problem recurring.
Also, keep in mind that the attic should be as tight as possible to outside air if you choose to install a dehumidifier. An unsealed attic means that the dehumidifier draws in moist outdoor air, which leads to higher energy consumption and lower efficiency. The tighter the attic is, the more energy efficient the solution will be! However, do not place the building sheet on top of the attic floor, as this can create thermal bridges. Building foil should be placed as close to the warm side as possible.
It is important to choose a dehumidifier that can cope with the actual humidity input - without having to run around the clock. Our RCF series dehumidifiers also measure both temperature and relative humidity and can therefore be controlled based on the mould index. This can be useful in winter or during cold periods, when you can allow a higher relative humidity, which saves both energy and extends the life of the dehumidifier.
Choose a model with a control panel that can be mounted easily accessible and highly visible downstairs in your home. This way, you can always keep an eye on humidity, operating mode and any alarms without having to go up to the attic. This is particularly important when the attic is sealed, as it reduces natural air exchange and requires more continuous monitoring.
Unlike condensation dehumidifiers, which quickly lose power in cold spaces, a Acetec desiccant dehumidifiers excellent even in unheated and humid winds. It reduces humidity quickly and keeps it at a safe level all year round. In addition, it is quiet, energy efficient and especially adapted to our Nordic climate.
We at Acetec AB have long experience of solving moisture problems in Swedish homes. Our desiccant dehumidifiers are developed and manufactured in Älvsbyn - to cope with the Swedish climate and our high demands on indoor environment.
💡 Feel free to try our digital tools to find the right model, or contact us directly we will help you choose a solution that minimises the risk of moisture, mould and odours in your attic.
