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  • Writer's pictureJulia Kaufmann

Healthy Home – Part 1: Mold Prevention, Ventilation and ERV Systems

As the first warm rays finally reach our little town, we are all basking in the knowledge that real spring is right around the corner. It was mere weeks ago that we were bracing against arctic blasts, trying our best to keep the pipes from freezing and the windows from icing over.


Living in North Idaho comes with its own set of climatic challenges. Whether it’s trying to stay warm in the winter, dry during mud season, or cool and smoke free during the blistering summer months, our homes play a crucial role in keeping us safe and comfortable.


We statistically spend four fifth of our life inside our home safest. Ideally they are the safest, most comfortable space for us and our loved ones. As it stands, however, our homes can be the leading source of toxicity in our lives. Unfortunately, this is not limited to the usual suspects asbestos, lead, and radon.


In this series, we are diving into the steps that make a healthy home.


Today, only 10 percent of American homes are insulated to meet the standards set in the 2012 International Energy Conservation Code. Low insulation not only means higher-than-necessary heating costs, but it substantially increases the risk for mildew and mold growth in our homes. Mold toxicity is a leading cause of illness throughout all ages. It weakens the immune system to make us more susceptible to a myriad of health complications ranging from more frequent colds, to autoimmune diseases, and cancer.


Mold comes in different shapes, sizes, colors, and toxicity levels. Most of us are familiar with black mold, one of the most dangerous versions of this ubiquitous life form. Most types of mold prefer a similar environment: Mold loves moist, poorly ventilated spaces with plenty of organic matter to feast on. If a house is poorly insulated, be it new or old, it provides the perfect foundation for extensive mold growth.


During regular life at home, we generate a lot of moisture in our environment. We produce moist air when we breathe, cook, take showers, wash dishes and do the laundry. On an average day, a person will release about 2/3 of a gallon of water into the air.


At this point, things become somewhat scientific. We have all seen windows in the house fog up on a cold day. The scientific reason behind it lies in the magic of relative humidity. Warm air can hold more water than cold air. Relative humidity tells us how much water is suspended in the air versus how much water the air could hold at its current air temperature. A comfortable interior has a relative humidity between 40-60%. If that body of air cools down, it can hold less water. So the exact same amount of moisture in the air might be a comfortable 50% at 65 degrees, but it will start condensating (i.e. reach 100% relative humidity) at 45 degrees. In other words, if comfortable interior air cools down twenty degrees, we will suddenly see condensation. We experience that on cold days: every time we breath out warm, moist air, our breath cools down and the moisture condensates and creates clouds of condensation in the air.


On cold morning hikes, that’s no problem. The same goes for the car; we can simply wipe away the condensation from the windshield, crank the heat and go on. However, things get dangerous in our homes. In most homes, the warm, moist interior air with that comfortable level of humidity penetrates into the (often under-insulated) walls. The walls separate the warm interior from the cold exterior. That means the inner part of the wall will be fairly warm, and the closer to the exterior siding it gets, the colder it becomes. Using our example from above, the 65 degree warm interior air – and the moisture bound in it –  will penetrate into the wall, and quickly cool down 20 degrees (and more), at which point the moisture in the air will condensate. Scientifically, this is called the dew point. The condensate (i.e. water) will then sit in the walls, and cause mold and mildew growth.


In some houses, you may notice water condensating on the interior walls. This is a result of drastically under-insulated walls, where the interior walls are so cold that the dew point is on the wall surface. It makes the home very prone to both structural and surface mold.


In order to build healthy, efficient homes, we need to take a multitude of preventative measures to ensure good interior air quality, a low mold load, and high energy efficiency.


A crucial element of a healthy home is proper ventilation. It will take care of most issues, from VOCs, to mold spores, to humidity fluctuation. Back in the day, houses were built as to not be air tight. Windows were notoriously drafty, floor boards shrank with age, and the lack of dense-packed insulation meant there was a steady throughflow of air. As problematic as that is for energy efficiency and, let’s face it, comfort, it did contribute to better indoor air quality. As the building codes become more stringent, homes are becoming significantly more airtight. Unless intentional steps are taken to ensure proper ventilation, the interior air quality can become highly toxic with high mold loads, toxins, VOCs, Radon, and low oxygen levels.


The modern approach to improving interior air quality and mitigating mold toxicity is the installation of a ERV or an HRV system. While varying slightly in their exact method of operation, both systems essentially supply the house with a constant stream of fresh exterior air, while sucking out stale interior air. The supply ducts are typically installed in the main living areas, such as the great room, and the bedrooms, while the exhaust ducts vent from high moisture areas such as bathrooms, laundry rooms, and basements. As if the idea of having fresh air streaming through hour home, and taking out toxins, CO2, Radon and mold spores wasn’t good enough, many systems come with the option to add additional filters for those pesky smoke days, meaning you’ll be breathing crystal clear air on even the smokiest of days.


Another aspect of mold mitigation most often sadly neglected are vapor retarders. We will cover that exciting topic next week.

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