Mold needs 55% or higher humidity in order to grow. Also, remember that reducing humidity below 30% isn't a good idea, either. This can cause health problems, making your eyes nose and skin dry, and exasperate lung and skin conditions.
If there are no cold-condensing surfaces and the relative humidity (RH) is maintained below 60 percent indoors, there will not be enough water in those materials for mold to grow. However, if the RH stays above 70 percent indoors for extended periods of time, mold will almost certainly grow.
Ideal humidity – and signs of trouble
Every home is different, but a level between 30 and 40 per cent humidity is typically ideal for keeping your home warm and comfortable in the winter, without leaving condensation on the windows. In the summer, that level can be higher, between 50 and 60 per cent.
Damp and high levels of relative humidity (RH), typically above 70–80%, are known to provide mould-favourable conditions.
Many of us assume that mold only grows in warm and humid environments, but that is not entirely true. Although mold growth may be slower in colder environments, it is still possible under the right conditions. In fact, some species of mold are known to thrive in temperatures as low as 32°F (0°C).
The mold spores will not grow if moisture is not present. Indoor mold growth can and should be prevented or controlled by controlling moisture indoors. If there is mold growth in your home, you must clean up the mold and fix the water problem.
However, if your air is too dry, it will be hard on the mucous membranes of your body. You'll want to make sure that you're living in a relative humidity of at least 35%. Remember, mold grows best at a relative humidity of 55% so keeping the humidity well below that percentage is your safest bet.
The temperature in your home
Keep doors of unheated rooms open to allow some heat into them. Ideally your home should be heated between 18 to 21 degrees Celsius, but older people, babies and people who are less mobile may need it to be warmer.
Most yeasts and molds are heat-sensitive and destroyed by heat treatments at temperatures of 140-160°F (60-71°C).
In short, ideal humidity levels in the winter months are almost always between 30-50%. Maintaining this range will help prevent dry skin, respiratory problems and even damage to wood furniture.
What is healthy humidity? It is recommended to keep indoor relative humidity between 30 to 50 per cent, if possible.
The world's lowest recorded relative humidity value occurred at Coober Pedy in the South Australia desert. The temperature was 93 degrees and the dew point was minus 21 degrees, producing a relative humidity of less than 1 percent.
Some molds can take hold and form a new colony in one or two days on damp ma- terials. When the relative humidity is low, the tem- perature is too high or too low, or the organic mate- rial is gone, molds go dormant.
By allowing air to circulate, adding light, and keeping the humidity down, you can stop mold before it starts.
Mold hates light. Other than moisture there's nothing mold loves more than dark places. An easy prevention against mold growth is opening your blinds and shades. If it's warm enough out, open the windows.
Mold is an obvious health risk in any home, but investing in an air purifier can help limit your exposure. The best among them will ideally offer HEPA-level filtration, with this level of filtration being able to trap up to 99.97% of airborne particles down to 0.3 microns in diameter.
The water in the air then condenses on colder surfaces: visible, for example, on the typical fogged windows in the car and in the home. But condensation also forms on exterior walls that are too cool and can increase the risk of moisture penetration and thus mold growth there.
Sometimes, humidity or dampness (water vapor) in the air can supply enough moisture for mold growth. Indoor relative humidity (RH) should be kept below 60 percent -- ideally between 30 percent and 50 percent, if possible. Low humidity may also discourage pests (such as cockroaches) and dust mites.
Best Humidity for Sleeping
The best relative humidity for sleeping and other indoor activities has been debated. According to the Environmental Protection Agency, the best indoor relative humidity falls between 30% and 50%, and it should never exceed 60%. Other studies suggest 40% to 60% is a better range.
During the cleanup of mold, many spores may be released into the air. To prevent health effects, there are several ways you can protect yourself while cleaning up the mold. Anyone with a chronic illness, such as asthma or emphysema, or who are immune comprised, should not do the cleanup.
Mold spores become airborne and can be spread throughout the house via the HVAC system. But they can also travel from the basement to the rest of the home on: Clothing.
While painting over mould may temporarily disguise the problem, paint alone will not kill mould. Instead, the mould will continue to grow underneath the paint until it begins to show through. It may also cause the paint to bubble or flake, ruining the finish. If possible, it's best to remove the mould before painting.