Growing Mold?

all about mold & why it’s important to you + 5 ways to eliminate mold growth in your home

In case you’ve grown suspicious of all this fear-mongering-talk of mold problems, don’t worry because there’s nothing you can do to eliminate all mold and mold spores inside your home. Sorry! What’s worse, mold can cause health issues – primarily allergy related – and in some cases, potentially toxic substances. But the good news is you can definitely do things that will help you prevent mold growth and exposure so that it doesn’t grow out of control.

But the question is, “why is mold all of a sudden a big deal?”

There are two really good reasons – 1) building materials have changed, and 2) building code has mandated the use of insulation. Basically, if we didn’t care about comfortable homes made with stronger materials, we wouldn’t have much of a mold problem at all.

So what is mold, and why does it grow inside walls, attics, crawl spaces and underneath wall paper, paint, and carpet?

Mold is actually an important part of our natural environment. In nature, mold helps stuff rot. Little mold spores float around until they find wet surfaces where they can feed off of cellulose – which is the carbon form of sugar that is found in green plants. And it is used to make a whole lot of commercial products from cardboard to adhesives.

The problem is that homes often promote moisture and condensation on materials that are made from dead plants—like engineered lumber, plywood, OSB etc (see Joseph W. Lstiburek’s article “The Material View of Mold”).

Where our former building materials consisted of simple and unprocessed timbers and large boards that mold could not burrow through to get the glucose polymer (sugar), today’s building materials are heavily processed with all the dead-plant insides and outsides mixed together for mold to burrow through, feast off of and grow on.

So what’s moisture got to do with it?

So now that we’ve given mold a lot of good food to eat, it only needs moisture to find it. Moisture in homes is caused by two primary sources – relative humidity and temperature differentiation. So preventing mold has a lot to do with how a home is constructed to account for condensation caused by outdoor air infiltration and humidity caused by indoor activities.

For instance, relative humidity is raised when you take a shower, run the dishwasher, water house plants, fill up the whirlpool and cook dinner (for more, see Peter Yost’s article, “Moisture Sources, relative humidity and mold” at GreenBuildingAdvisor.com). These activities cause water vapors that can be trapped inside walls and settle on building materials.

To make matters worse, homes are both air conditioned and better insulated today than they were in the past. And what is the point of conditioned and insulated space? Temperature differential. Most of the time, you want the temperature inside your home to be different than the temperature outside your home. And what does temperature differential promote? Condensation. And where does this condensation take place? Inside walls, in attics and in crawl spaces. Why? Because when air’s temperature goes up, it can absorb more moisture (humidity), and when it goes down, it sheds moisture (condensation). So when hot humid air meets cool 72 degree lumber, it condenses—causing mold, mildew, rot and mites where you’ll likely never see it.

So here's what you can do about it?

Now that we see how our lifestyle, building materials and construction methods promote mold growth, it’s time we talk about how you can keep it from becoming a problem. The truth is that we’re simply not going to stop producing humidity inside our homes. Hot tubs, fireplaces, dishwashers, and natural humidity are all apart of our modern-day high standard of living. And we can work around these issues using a few simple innovations.

So here are 5 effective ways to prevent mold growth in your home.

1. hygrometer – get one. It will tell you the relative humidity inside your home. You can know when RH reaches 70% or more and the go turn on your dehumidifier. Plus, they’re really cheap.

2. dehumidifier – get one and turn it on. Especially when your hygrometer tells you that the RH is nearing 70%.

3. Ventilation – you cook, you shower, you wash clothes and dishes. These activities contribute to a higher RH. That’s why it’s important to have a ventilation system that pulls the warm humid air out from your home.

4. Air sealing – when building new, adding on or remodeling you have the opportunity to significantly reduce (if not eliminate) mold growth within your walls. Air sealing is when the home’s sheathing is glued to its framing. This stops airflow. We also use spray-in open cell insulation around all wiring and ductwork to prevent any and all cracks. This prevents warm humid air interacting with cool air and building materials.

5. Rain screen – a completely sealed, high-density, vapor-permeable and water resistant wrap around the entire home between its sheathing and framing will prevent moisture from penetrating the home but allow water vapor to escape without causing damage. Furring strips (vertical strips of wood) between the wrap and siding also create an open space that allows for natural cooling and drying.

From a sustainability standpoint, mold is a symptom of a much larger problem – the lack of durability and energy efficiency of a home. And if we don’t build houses that promote moisture control and eliminate condensation inside of walls—well, we haven’t built homes worth living in. To learn about what else makes homes green, download (re)source.