Some people like math and others like history. I prefer biology—but only when it comes to buildings and construction. The practice of building biology may be new to some people, but it has been around for thousands of years. For a contractor, understanding and implementing building biology can give you a competitive advantage and make your company stand out.
When we talk about building biology, we are talking about the impact of the indoor environment on our health. Building biology comes from the German term bau-biologie.
According to the EPA, Americans spend most of their time indoors, where the concentration of some pollutants can be two to five times higher than typical outdoor concentrations. With allergies and chemical sensitivity on the rise, more people are seeking out building contractors who use materials, design techniques, and installation practices to create healthy indoor environments. There are a variety of topics related to building biology and healthy buildings, but I would like to focus on one subject today—mold.
Mold has many implications, and most of them are unpleasant—musty odors, damp basements, moldy carpets, water leaks, and unappealing patches of fuzzy growth on soggy drywall. Mold can be hidden within walls, inside cabinets, and under flooring, and the health effects on the occupants and the structural integrity of the building can be severe. The key to mold control is moisture control.
Mold can develop in many different areas. Proper drainage around the foundation is critical and non-toxic dampproofing is an option. In some conditions, water can move up through the soil and dampen the basement floor slab. This is known as capillary action. Creating a capillary break under the slab can stop this type of moisture invasion.
Wall construction should include kiln-dried wood that is completely free of mold and mildew. Fir, spruce, or hemlock is preferred over pine where available. Preventing framing lumber from getting wet during construction is important. Any wood treatment to prevent insect and mold infestation should have low toxicity.
Building insulation in the wall cavity can have a major impact on moisture control throughout the building. The opportunity for moisture to dry out from within the walls has been reduced due to the air tightness of homes. Trapped moisture can lead to mold and wall assembly failure. Wall designs that discharge moisture from within have been around for hundreds of years. Building insulation should be moisture resistant, non-toxic, dust free, and emit no off-gasses.
Proper soffit and overhang design can keep rain off the windows and shade the summer sun while allowing the winter sun in through the windows.
Clay-based plasters can provide superior wall finish because of the remarkable hygroscopic properties of clay and can be an alternative to drywall. Clay has the natural ability to regulate indoor humidity by absorbing moisture when the air is too humid and releasing moisture when air is dry. Natural beeswax finishes will protect the walls while maintaining its permeability.
Ideal humidity levels in a home range between 30% to 50%, although this can vary between individuals. Adequate ventilation is critical in stopping mold growth in areas that create high levels of moisture, such as kitchens, bathrooms, saunas, and pool areas. This is especially true in crawl spaces due to moist soil. Moisture in a crawl space can travel up through walls into the attic area, creating ice crystals in the winter and wet ceilings on the second floor in the spring.
If you suspect mold in your house, it is wise to contact a reputable professional to do a thorough investigation.