How do I winterize my home against mold?

Jeff Bookout
October 14, 2020

Reading Time: 4 minutes

As winter approaches, we asked BioBalance resident expert Jeff Bookout what folks can do to their house to prepare for winter.


It’s not so much, “How do I winterize a home for mold?” because a lot of times during the wintertime things generally get better. One of the things that naturally occurs when the wintertime comes is the humidity automatically drops, and that helps mold growth get under control. When it comes to controlling mold, removing the source is key, then dilution is the solution (fresh air into the home).


Winter’s Lower Humidity: Good. Lack of Fresh Air Indoors: Bad.

There are three things that make people sick from mold:  mold spores/fragments, mycotoxins, and MVOCs (microbial volatile organic compounds). While everyone looks for mold spores in the air, you might actually have mold growth you can’t see behind a wall, in the ceiling, in a crawlspace, in an attic, etc. In the wall cavity, mold is fat, happy, and content as nobody is messing with it. So mold spores aren’t necessarily high in the air, but the mycotoxins and the MVOCs are. Mycotoxins and MVOCs are like Scooby-Doo green gas. If you can picture mold throwing “green gas” into the air, and that is what is making people sick— not just the mold spore, but the mycotoxins and the MVOCs.

Now in the summer, when we open windows up in a building or home we get fresh air exchange and mycotoxins and VOC are diluted. But in the wintertime, we shut everything up and the mycotoxins/MVOCs stay trapped inside the building envelope and the building fills up with those toxins.

I would recommend that everyone look into a HRV or ERV system. HRV stands for, Heat Recovery Ventilation, which is best for cold climates and ERV stands for, Energy Recovery Ventilation, for hot climates. These systems bring in fresh air from outside and take inside air and push it outside. The air goes through an exchange box, which doesn’t let the different air touch, and yet captures about 80% of the cool or heat (conserving energy). It’s a good way to change out the air in your house several times a day without having to have your windows and doors open.

Q: I’m sure we would all love to get an air exchanger, but is there anything we could do today without one? 

Besides opening your windows and doors to occasionally vent your house, you can keep a vent fan on and crack a window. You should have a vent fan in your bathroom. Ensure that it is venting outside your house and not directly into your attic. With the fan, you are taking that air in the house and throwing it out. It’s not a complete air exchanger, but it is a cheaper way to do it. Cracking a window ensures that you are bringing fresh air in and not just pulling in dirty air from the wall space and ceiling space.

In a pinch, you can get contaminated air out of your home using a fan, as long as it is not exhausted in your attic.


Reduce Dust to Reduce Mold

When we transition from warmer months to cooler months, we move away from air conditioning and start using our heaters. Before my heater kicks on for the first time, I like to change the HVAC filter with at least a MERV-11 (filter rating). This helps me remember to do it, and helps reduce particles in the air, which include mold spores and fragments. It is also very helpful to run a stand alone HEPA filter in the home throughout the winter to keep those particles to a minimum.


Keep the Humidity Below 50%

Many people like to use humidifiers during the winter. This is fine as long as they are kept clean (filter, filter housing, and drain line) and do not result in any area having humidity above 50%. Also keep in mind that if your home is sealed up tight, the humidity may increase (especially during cooking or with a bunch of people inside). This may result in condensation on windows that could lead to mold growth. So, keep it dry and keep the humidity low. We recommend buying a $15 hygrometer online to monitor humidity levels.


Using Haven Fog & Haven Mist

I would also recommend what I do in my own house because my youngest daughter gets sick from mold exposure. Each month throughout the year, including the winter, I use HavenMist to treat my house. It takes just a few minutes and it is inexpensive. Then once a year without fail, I fog my own home with HavenFog. I only test the air if I suspect a problem (e.g. – after I have a water leak or water intrusion issue).

Those are excellent thoughts. Jeff, thanks for your time.