Building Biology and the Healthy House
Building related illness, 20th (21st) century disease, multiple chemical sensitivities, sick building syndrome, environmental illness: these terms are recent additions to our vocabulary. Until about 25 years ago, indoor air pollution was a very limited phenomenon, but three basic things have changed in the evolution of building technology resulting in the current widespread concern about the environmental quality inside our homes.
First, the very fabric that our homes are made of has changed. Postwar industrialization has introduced mass produced building components and transportation networks to distribute these products nationwide. Building materials and methods, once regionally derived, have been replaced by these manufactured components that promised to provide better performance for less cost. Have these products fulfilled this promise? Certainly not when environmental and life cycle costs are added into the cost equation. Furthermore many of these new products have had a negative and costly impact on our health. Thousands of synthetic chemicals have been incorporated into manufactured building products. Whereas at the turn of the century and for thousands of years preceding this century, our built environments were free of man-made chemicals there are now more than 4 million registered man made chemicals, 70,000-80,000 of which are in common use. We know very little about the health effects of most of these chemicals and even less about what happens when they interact with one another in an enclosed environment. We do know that many chemicals found in building products, and once thought to be safe, are making people ill.
At the time of the first energy crisis when the cost of home heating and cooling skyrocketed we recognized the need for more energy efficient building. In solving one problem we inadvertently created another that further contributed to the demise of our indoor environmental quality. For several decades now newer, better technologies have been introduced to seal homes more tightly thus making them more energy efficient. However in order to maintain health, a well sealed home that prevents air leaks requires a ventilation system to replace stale and humid air. The need for fresh air exchange is especially significant in standard home construction given the number of synthetic, and fuel derived toxins that we had now introduced into our homes. And yet none is required by law and most tight homes are insufficiently ventilated.
Thirdly we have become accustomed to a new level of comfort, convenience and sanitation undreamed of just 100 years ago and these amenities have placed unanticipated performance demands on our buildings. We have introduced huge amounts of moisture into our homes through daily indoor hot-water bathing, and through the use of laundry and dishwashing appliances. In addition, with the advent of modern HVAC equipment, modern architecture has replaced climatically responsive vernaculars design in favor of the mechanically dependent “machine for living in”. And while we have succeeded in equipping our homes so as to provide uniform temperature 24/365 regardless of climate we have created extreme moisture and temperature differentials between the inside of our homes and the outside environment. The stresses placed on our building envelope have contributed to widespread envelope failures and further health threatening conditions such as mold.
In response to the problem of building related illness, two very different models for the healthy home have emerged. The first more mainstream approach involves eliminating as many pollutants as possible from within the building envelope and sealing it very tightly on the inside so that there is less need to worry about the chemical composition of the structure or insulation. Clean, fresh air is then mechanically pumped in, keeping the house under a slightly positive pressure so that air infiltration is controlled and pollution caused from human activity is successfully purged from the home. This is a technologically based solution to a technologically based problem. Impermeable or “sealed” wall construction is a relatively new concept that relies on manufactured synthetic products to create diffusion retardant walls. Mainstream building practices and codes are now based on sealed construction theory.
The second approach involves building the structure out of natural or nontoxic materials that are permeable. Adobe, light clay, rammed earth and straw bale are examples of wall systems that fall into this category. The building is seen as a third skin (clothes being the second) — a permeable organism interacting with the natural world and facilitating a balanced exchange of air and humidity. This approach is based on the precepts of “Building Biology”. The harmonious interaction with nature is the model upon which the Building Biology principals of healthy building are derived. It recognizes that humans are a part of and not apart from a greater natural system. While technological innovation has been somewhat successful in both dominating and replicating the natural environment many of the subtle benefits provided by nature have been overlooked (for several decades, as mentioned above, the need for fresh air was one such subtlety). The Building Biology vision of a healthy indoor environment encompasses several criteria that are not often considered in more mainstream technologically based approaches to the healthy home. These include the study of the building site for geopathic disturbance, the role of breathable naturally derived materials in facilitating balanced humidity, the elimination of man made electromagnetic fields, and the use of color, light and harmonic proportions in building design.
Ironically, building systems that use natural materials as their base, once the norm for us and still the norm for the majority of humankind, are viewed with great suspicion and skepticism in the current mainstream building culture. If one chooses to build with natural materials one quickly learns that natural building systems have become the orphans of the modern building industry. Whereas huge corporate resources back industrialized building products, funding for code required testing of natural non-proprietary materials has, to date, been a grass roots pass-the-hat affair. Even though people have surrounded themselves with natural permeable materials throughout human history and even though enduring models of these buildings are found throughout the world, mainstream building practices and codes are dominated by manufactured building commodities that are laboratory tested, standardized, stamped, packaged and shipped. When one applies for a building permit, for a home to be made with natural building materials the applicant may be rejected, or if permitted, the building may bear a dubious “experimental” status.
The natural building movement championed by the theories of Building Biology and a small but growing sector of environmentally concerned builders, designers and homeowners is however gaining momentum. And I believe there is a synthesis at hand between the two seemingly opposite approaches to healthy building. A natural home equipped with all the amenities of modern life faces many of the same indoor environmental qualities as does a sealed construction and ventilation systems are becoming more common in natural buildings. On the other hand manufactured, code pre-approved permeable wall systems such as aerated autoclaved concrete are being introduced in to the mainstream market place. Straw bale construction has now been tested and codified in many locations. More and more construction products now advertise being “environmentally friendly” and “non-toxic”. Green building rating systems that reward healthier building practices are springing up all over the country. Regardless of the starting point we are moving towards healthier homes that are freer of toxic chemicals, more energy efficient and kinder on the environment.