There is an ideal relative humidity range for our health and that is somewhere between 35% and 55%. In modern life we have introduced many new sources of moisture into our homes. Daily showers, laundry, cooking and dishwashing tend to create concentrated bursts of humidity. Because conventional construction can tolerate very little increase in humidity without condensation/mold problems moisture from these sources must be mechanically sucked out of the home. At the same time most heating systems tend to make the air too dry for optimum health, and so homes must be humidified to reach healthy levels. So on one hand, we are using technology to suck moisture out and on the other, we are using it to add humidity back in! Is there a better solution.
This adobe building designed by Paula features naturally sealed earthen floors, interior, unfinished adobe walls, unsealed woods and clay-based plaster. It has built-in capacity to regulate the interior climate.
Building Biology explains how we can maintain healthy humidity in our homes by working with nature. Certain building materials such as unfired clay, wood and natural fibers have the ability to naturally regulate indoor humidity provided they are not sealed with impermeable finishes. They can effectively capture humidity when the levels are too high and then release it again once the ambient levels drop thus buffering these extremes and creating natural humidity ranges. This material characteristic is known as hygroscopicity. This explains one aspect of the value of using natural unadulterated building materials, finishes and furnishings. Although exhaust fans are still a good idea they are a supplement and not a dire necessity for the health of the home.
There is a trend in conventional construction to take the exact opposite approach in finishing our homes, making everything impervious for ease of cleaning and maintenance. Surfaces are covered with a thin layer of plastic in the form of various types of man-made polymer finishes. While these wet applied finishes were once a great source of indoor pollution, there are now many choices for low-zero VOC synthetic finishes. Although with careful selection it is now possible to apply synthetic finishes without releasing poisonous gasses there are a number of subtle consequences to consider. These include:
An imbalance in the electro-climate that manifests in frequent static electric shocks
Reflective surfaces that have a negative impact on the acoustics and can create visual glare
A loss of hygroscopicity which leads to imbalanced and unhealthy ambient humidity
Here are some ways to introduce a higher level of hygroscopicity into our homes:
Use natural finishes that maintain porosity such as beeswax and natural oils
Use unfired clay in the form of clay plasters or exposed earthen walls and floors.
Don’t seal wood surfaces where a seal is not required such as ceilings or on exposed timbers
Use natural cottons and wools instead of synthetic fabrics for upholstery and drapery
The benefits of natural finishes go well beyond visual appeal. They aren’t maintenance-free. They require occasional re-application but they patina with age and these natural finishes reward us daily with a better indoor environment. It is a life-style choice.