Humidity in our homes is something we all try to avoid. It causes mold, moisture, creates condensation on our windows and is unanimously undesirable. However, humidity is not only a nuisance that we find unpleasant. As Harvard’s Annual Review of Public Health recently announced, there is over forty years of overwhelming evidence to suggest that human health is influenced by the buildings we all live and work in. By monitoring our Indoor Air Quality, we can avoid any adverse effects that stem from humidity. Not only can high humidity levels influence our homes and health, but overly low humidity levels are now known to help the spread of infection. It is estimated that globally 10 to 20 percent of homes are affected by some measure of dampness, so we at Airthings have compiled expert advice for everything you want to know about humidity.


What causes humidity indoors?

In layman’s terms, humidity refers to the amount of water vapor present in the air. A relative humidity of 100% would mean that the air itself is saturated, it is unable to hold any more water vapor, so it rains. Relative humidity is the most common indicator often used by weather forecasters and our experts at Airthings. The calculation of relative humidity can consider the fluctuating temperature at the present moment. The higher the temperature, the higher amount of water the air can hold.  

As humidity is simply the amount of water vapor present in the air, a multitude of things can cause these levels to fluctuate.  Anything from drying laundry to leaks can give off moisture which can lead to humidity. Even the moisture trapped in warm air can touch cold walls and revert to water. This is nothing to worry about, unless the levels get excessively high or excessively low. In this case, increase the ventilation or reduce the moisture through proper ventilation.

Humidity and immunity

Superficially, creating indoor environments with low levels of humidity would appear to be the natural solution. The dryer air would combat mold, however as we shall see, too little will also cause problems. In fact, low humidity and low temperatures have been found to  alter the transmission of infectious disease particles, such as the influenza virus. Therefore, low humidity levels actually facilitate the spread of infection, thus affecting the immune system.

Humidity and asthma

As most people are aware, high levels of dampness and humidity can supply enough moisture to facilitate mold growth. Not only this, but mold has been linked to asthma. Asthma is an incredibly common condition that makes it difficult to breathe. The Harvard Review found that 21% of the 21.8 million cases of asthma annually are attributable to residential dampness and mold. This means that the unsightly problem can additionally cause detrimental health effects.

Our experts have compiled a list of selected not-for-profit organizations that provide fantastic information regarding asthma should you require it:

Asthma and Allergy Foundation of America

The National Health Service, UK

The Norwegian Asthma and Allergy Association

Humidity and employers

This is further problematized for employers, who are said to have received increased reports of itchy, watery eyes, headaches, throat irritation, respiratory symptoms, increased heart rate, negative mood, SBS symptoms, and fatigue from employees. This was associated with unfavorable heat, humidity, and ventilation conditions. Not only is sitting in a stuffy, hot or worse humid workplace frustrating, it can also have negative effects on your health. So much so, that there is an increase in common workplace irritations. Moreover, research found that “Increased water damage and mold have been found to negatively impact workplace productivity, job performance, quality of life, absenteeism, and classroom learning for office workers, teachers, and schoolchildren”. Therefore the impact is not only for adult office workers, but has potentially widespread effect of various age groups and areas.

Quick humidity solutions

The United States EPA recommends that relative humidity levels should not exceed 59% or fall below 30%. Quick fixes like those we have listed below can often help manage your humidity levels. However you must first be sure that there is not a larger underlying issue such as pipe leaks, or subpar insulation in key areas. Successful ventilation inside of your home will help create a relatively constant humidity level that adheres to recommendations, you just need to monitor the levels to make sure.

Easy, expert tips which will help to reduce the indoor humidity levels in your home:

  • Bathroom fan.
    Installing a bathroom fan can help to improve air circulation in the bathroom where warm, damp air accumulates.
  • Range hood.
    A range hood is a mechanical fan situated above the oven, stove or cooktop in the kitchen. It helps to extract steam, heat, cooking fumes and odors from the air.
  • Washing line. 
    Drying clothes on a line dryer out of doors will help combat the amount of moisture you are bringing into your home.
  • Air conditioning.
    A very easy solution, but not always the most cost effective.
  • Replacing air conditioning filters.
    Replacing existing air conditioning filters will help to ensure fresh air is being circulated
  • Dehumidifier. 
    It does what it says on the box; an electrical appliance that reduces and maintains the humidity in the surrounding air.
  • Indoor plants.
    In particularly humid rooms of your home, it may help moving the house plants to other areas, as plants release small amounts of moisture.
  • Opening windows.
    A little more challenging in the colder months maybe, but simply opening a window allows fresh air to come into your home and improve air circulation.
  • Still no luck? Try not-for-profit resources such as Energy Saver, by the US Department of Energy. They have tons of further tips to help with home ventilation and moisture problems.


Humidity is one component of a wider consideration that makes up Indoor Air Quality. As society spends more and more time indoors, the importance of Indoor Air Quality is rising. You can measure your humidity levels. More often or not people do not measure and only realise it is high once mold has already formed. Similarly with Radon gas, people are often not inclined to measure for it until they are made aware of being in a high risk area or selling their home requires it. The Airthings Wave can continuously test for relative humidity levels in your home. Meanwhile, it additionally measures for Radon and temperature, all of which impact your Indoor Air Quality.