Reducing Mold and Mildew in Guestrooms 

Mold and mildew damage is an issue for all hotels and commercial buildings.  It doesn’t favor any particular geographic area; rather, it targets all parts of the country from the East Coast to the West Coast. 

Mold and mildew starts out as harmless and everyone thinks it’s easy to get rid of.  The truth is it’s not easy to get rid of it.  Mold and mildew are actually micro-organisms living together in large colonies.  As long as moisture and oxygen are present, mold and mildew can grow on virtually any organic substance, such as wood, paper, carpet and insulation.  As the spores associated with it grow, you eventually have smelly, black spots that are not only evident to the guests and associates but unhealthy for them as well. 

In a hotel guestroom, there are a few breeding grounds for mold and mildew.  Vinyl covered walls that many brands require are perfect environment for mold and mildew.  The cellulose backing of the drywall along with the wallpaper glue is favorite foods for mold and mildew.  When the AC is on, the vinyl wallpaper gets cold and blocks condensation on its underside.  This allows moisture to accumulate and mold spores to grow.  Paint over interior drywall is another breeding ground as it traps moisture and allows the spores to grow as well.  Window or roof leaks can also add moisture to a guest room and aid in the growth of mold and mildew.  

Mold and mildew need air, food and water to survive.  If any or all of these components are reduced or eliminated, the mold and mildew will stop growing.  We can’t eliminate the air or food but we can do something to reduce the moisture in the guest rooms. How can we do this? 

During construction or a renovation, moisture is commonly absorbed into the sheetrock and then trapped behind paint or vinyl wallpaper.  About a year after the construction or renovation is complete, a survey looking for moisture should be done to determine if there is any mold or mildew present.  If moisture is found, the drywall should be removed and replaced.   

In hot, humid climates, guests tend to enter a room and set the thermostat as low as it can go. They then leave and when they come back the room is freezing and wet.  It’s become a perfect environment to grow mold and mildew.  Each time a guest opens a door or window, moist warm air will be introduced into the environment.  A digital thermostat will help prevent this because it can be programmed to not allow guests to turn the thermostat down past 68˚F. 

Windows and doors, HVAC units, ceilings and floors are all potential locations where mold and mildew can grow. You’ll want to examine the guest room windows and doors and repair any water leaks that you find..  You should also ensure that the window and door seals are in good shape as they can become brittle and ineffective over time. You’ll want to repair any broken seals around the HVAC and make sure outside vents are operational and not stuck open. Any water leaks on the ceiling should also be repaired.  If your floors are on concrete, you should check to make sure that there is a vapor barrier between the sub-floor and carpet.   

We all think that the air conditioner will remove some moisture in the room.  The moisture reduction occurs only during the actual cooling process until the thermostat is satisfied (it gets to the setting).  Once that happens, no more moisture reduction will occur.  The ideal size for a guest room AC unit is 6,000 BTU.  It’s a common practice to install a larger unit but you don’t want to oversize the unit.  When you install a larger unit it only runs 50% of the time and, thus, doesn’t have the same effect on moisture. 

Occupancy sensors can also help in the reduction of moisture in guest rooms.  In unoccupied rooms, the thermostat can be set to run the circulating fan for 10 minutes every hour.  This will keep the air circulating and not give mold and mildew a perfect environment. 

According to scientists at the University of Florida, Gainesville, the most favorable zone for mold and mildew growth is a temperature above 72˚F and above 60% relative humidity.  Trying to stay within those guidelines is our challenge. 



Refer to which is and excellent guide to the indoor air quality issues in hotels
Refer to for health codes regarding mold in hotels 
Refer to which is a mold help organization which will help in location a local professional testing company 
Refer to which is from the Asthma and Allergy Foundation of America on mold allergy