Testing Attic Moisture and Temperature

Looking down the length of a long, dark attic with unevenly-spaced floor boards.
What You'll Need
What You'll Need

Attic moisture is caused by hot temperatures and high humidity are two of the prime causes of mold in your attic. It’s important to keep an eye on attic moisture and temperature if you believe you have a potential problem with mold.

Check for Excessive Heat

It’s impossible to find a constant temperature for your attic; it’s likely to vary from season to season and will also depend on how well insulated your attic is (insulation levels will also affect attic moisture). It will also depend on how well-ventilated your attic is. In the summer, for instance, an attic that had the correct amount of insulation but poor ventilation would be extremely hot.

Depending on the climate and outside temperature, it could reach up to 150 degrees Fahrenheit in the attic. To determine the temperature of your attic, use a total of 3 thermometers. One should be in the middle of the attic, suspended from the roof ridge (this will be the hottest part of your attic). The second should be close to the attic entry, and the third should be at the far end of the attic.

By taking an average between the thermometers, you’ll be able to gauge the temperature in the attic. You don’t want this to be too high or you will have moisture developing in the attic. The optimum temperature will depend on location and climate. From this you will also be able to see whether you need better insulation and ventilation in your attic and establish the steps to correct any problems.

Check for Excessive Moisture

There is specialized equipment to measure humidity in different rooms within your house, but it’s very expensive, and the results need to be interpreted by a professional. However, you can judge humidity and moisture levels in your attic purely by observation. If there is moisture running down the attic windows and pooling on the frames, the humidity is too high. The same applies if surfaces are wet to the touch. When this happens, the attic moisture is far too high.

Check for Insufficient Moisture

You can also have a situation where there is not enough attic moisture. Although this is rare, you can test for it by touching something metallic in the attic and seeing if you receive a jolt of static electricity. If this happens, it indicates that your attic is too dry.

Do Something About It

If you have excessive attic moisture, it greatly increases the chances of mold or mildew developing in your attic. To reduce it, add more ventilation. The simplest way is to increase cross-ventilation within the attic. This can be done by adding at least one more vent at each end of the attic. You’ll also improve ventilation by adding more vents over the soffits. Finally, remember to test attic moisture and temperature every season and keep records of what you find.