The Importance of Maintaining Relative Humidity in Your Vacation Rentals

Michael Driedger
7/28/2020

With the recent global COVID-19 pandemic, the subsequent lockdown and the inevitable negative impact on the vacation rental industry, moving forward we all know that winning back the trust and confidence of travelers will be paramount. Ensuring properties follow excellent cleanliness and hygiene procedures is a given, but property managers may also want to consider the air quality of their units. Including a simple humidifier in a rental can make a significant difference.

When I was growing up in the very dry plains of Saskatchewan, my parents would put a humidifier in my room whenever I had a cold or the flu. I loved the soothing hum it made, which helped me fall asleep. I always thought that the reason they put in the humidifier was to make me feel better. However, many years later, when I started working in building design and on hospital projects, I realized the humidifier was to keep them from getting sick, not for me to get well!

Prior to the COVID-19 pandemic, it was not common knowledge that viruses are airborne at below 40% relative humidity. We all tend to believe that the cold and flu season passes in late spring and summer because the temperature is warmer. However, the end of flu season is more likely to be because the air is more humid during the summer. In most countries, during the winter, heating the air dries it out to a humidity level closer to 20%—the perfect breeding ground for airborne viruses. Although studies on this date back to the 1980s, they are particularly pertinent now.

But first, what is ‘relative humidity’ (RH)? It’s called relative humidity because it’s relative to temperature. If the RH were to reach 100%, then it would be raining. With snow, we also know that the temperature can be very low and the relative humidity 100% (this is obviously happening in the sky).

In Canada, maintaining humidity levels is built right into the design requirements for a hospital. The requirement is that all operating rooms be maintained at above 40% relative humidity at all times. Prior to co-founding Operto, a property automation system that provides intelligent control of smart home/IoT devices for the short-term rental industry, I worked as a green building consultant, so I was involved in these building projects. Most buildings are only designed to maintain temperature levels and the only other projects that considered relative humidity levels were laboratories and archives. For these spaces, keeping humidity at the ideal human comfort range (40-60%) is also the ideal humidity level for most experiments, and keeping books and antiques preserved. One of those aspects: It stops viruses and bacteria from being airborne.

Monitoring the humidity level is also how to keep mold and mildew—often more of a problem in southern states—at bay, since mold growth usually starts at above 60% relative humidity.

So the big question is, if science tells us that people are more comfortable, mold and mildew less prevalent and that viruses are less present at between 40% and 60% relative humidity, why don’t more building types, including hotels and short-term rentals, design to meet this standard?

At home and in the Operto office we have always been very diligent in monitoring the RH to make sure it’s as close to 40% as possible. We do this by running humidifiers and monitoring RH using the same sensor that our hotel and property management clients use to monitor their properties. Whilst CO2 is my biggest indoor air quality concern in the summer, my biggest air quality concern in the winter has always been relative humidity.

Now it really is time for more property managers and owners to pay attention to RH. It’s just too important for human comfort and wellbeing not to make this a priority.