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Principles of Healthy Construction

By HHI Staff

Scientific studies have documented that the quality of the air indoors is sometimes deplorable. Often, as we go into a building, we enter an atmosphere that is considerably more polluted than the outdoors. There are a variety of reasons for this. One of the primary causes of indoor air pollution is our buildings are filled with synthetic materials that outgas a wide range of chemicals into the air. One study identified over 200 odorous compounds emitted from common building materials. Typical examples are: acetonitrile, methyl methacrylate, styrene, aliphatic hydrocarbons, ketones, alkenes, and esters. Some of these chemicals are carcinogens (vinyl chloride, trichloroethylene, benzene), some are sensitizers (formaldehyde, toluene di-isocyanate), and some are plasticizers believed to cause chromosomal damage. Unfortunately, most of the chemicals found in the air of our buildings have not been studied for their precise health effects. When these chemicals are released into the indoor air, often they cannot escape to the outdoors because of the tightness of many modern buildings.


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Walking into a modern building can sometimes be compared to placing your head inside a plastic bag that is filled with toxic fumes. It is no wonder that thousands of people are suffering from various building related illnesses. For many of the people that are being made sick by their house, school, or office, some major changes are necessary before they can regain their health. For a few people, non-toxic construction is necessary for survival. For the rest of us, non-toxic construction will help us to maintain our already good health.

What can be done to make our buildings more healthful? Fortunately there are some principles to keep in mind when building or remodeling that will help to considerably reduce the levels of pollutants in the indoor air. The three most important concepts to remember are elimination, separation, and ventilation.

Elimination is by far the most important principle to use when selecting construction materials. If you eliminate toxic materials in the construction of a building, there will be no toxic fumes to contend with. Probably the worst offenders are some types of carpeting and manufactured wood products. Paints, adhesives, and vinyl wall coverings are also often problematic. Unfortunately, these potentially polluting components are almost taken for granted in construction today.

Sadly, most building materials are chosen over less polluting alternatives primarily for economic reasons. It is usually not considered that if ill health is the result of using toxic building materials, the money saved could go toward medical expenses. Saving $20 on building materials may quickly be spent at the doctor. If, over time and long-term exposure to chemicals 0r mixtures of chemicals, cancer is the result, medical bills can often exceed the cost of the entire building. It makes economic sense to spend a little more on healthful building materials to spend less on health care. Increased productivity will be a side benefit.

Some types of new carpeting have been shown to outgas dozens of chemicals that can and do affect health. Examples include formaldehyde, xylene, ethylbenzene and methacrylic acid. While the outgassing decreases with aging, the synthetic fibers can continue to break off, contributing to house dust. This isn't just ordinary house dust, it is synthetic house dust. When it finds its way into the heating system, it can get burned and release tiny amounts of such undesirable fumes as phosgene and cyanide gases into the air. New carpeting often is treated with fungicides or other chemicals to kill the molds and microbes living there. These chemicals are designed to kill living creatures. Since we too are living creatures, these chemicals can negatively affect us. As the treatments are removed over the years by cleaning, the tiny creatures begin to thrive in the carpeting. Studies have shown that there can be tens of millions of microorganisms per square foot residing in carpeting. Not a very healthy thought. Of course, some of the bacteria will be relatively innocuous but mold spores and dust mites are common sources of allergic reactions.

Ceramic tile, slate, terrazzo, hardwood, pine, and colored concrete can be healthier choices for flooring materials. If desired, they can be covered with easy to clean natural fiber area rugs. Oriental and Navajo rugs can be very attractive and, unlike wall-to-wall carpeting, they can be taken with a homeowner if they ever change residences. In commercial buildings and offices, the healthier alternatives will be more cost effective if the entire life cycle is considered.

Manufactured wood products are to be avoided primarily because of their formaldehyde emissions. Medium density particle board can result in occupants being exposed to very high levels of formaldehyde. In fact, the only time the average person will be exposed to higher levels is after death, during the embalming process. Plywood and flakeboard products are somewhat less offensive, but there are many people who exhibit symptoms when exposed to their lower levels of formaldehyde. There are even sensitive individuals who cannot tolerate hardboard, with its very low levels of formaldehyde. Solid wood and other healthier materials can easily be substituted wherever man-made wood products are currently being used.

Formaldehyde is not only an eye, respiratory and skin irritant, but it is also a potential human carcinogen. It can induce asthmatic attacks and depress the central nervous system. According to an article in the Journal of the American Medical Association, 4% to 8% of the population could become sensitized to formaldehyde. Once sensitized, they could experience more severe and prolonged reactions to smaller and smaller exposures. 4% of the American population is about 10 million people. You, your coworkers, or a member of your family could easily be one of those affected.

Residential heating systems fueled by wood, natural gas, oil and kerosene have the ability to pollute a house with combustion gases and particulate matter. Anything with an open flame should be banned from a healthy building, including cigarettes. The major byproducts of combustion (nitrogen oxide, nitrogen dioxide, carbon monoxide) are well known indoor air pollutants to which many people are exhibiting reactions. Higher efficiency appliances with sealed combustion chambers are, of course, less polluting, as are fireplaces with sealed glass doors, but for people exhibiting hypersensitivity reactions there should be no combustion sources indoors.

Commercial HVAC systems are prone to other types of problems because of their complexity. Disconnected or contaminated fresh air intakes, ductwork with biological contamination from humidification equipment or plumbing leaks, poor air circulation patterns, and lack of maintenance are typical examples.

With immature immune systems, children are often the most susceptible members of our society to indoor pollution. To expose a child to the volatile chemicals outgassed from recent remodeling in a school makes very little sense. It has been shown that children living in homes with wood stoves have a significant chance of developing respiratory symptoms. The outdoor air pollution in areas where wood burning is common attests to the fact that in many cases, wood is not a clean fuel. Unborn children are also at increased risk, as are pregnant women, and the elderly and the infirm.

In Scandinavia, it is common to locate a natural gas furnace outside the house, to avoid polluting the living space. This idea could be adapted to houses in the United States.

If a normally aspirated combustion furnace must be located indoors, it should be atmospherically separated from the house. This means that the atmosphere of the living space should not be connected in any way to the atmosphere of the combustion chamber. By having a totally sealed air supply running from the outdoors to the furnace and then back to the outdoors, the combustion air supply and the combustion by-products will be separated from the air in the living space. This is important because many systems that are not separated in this manner have been found to be backdrafting. When this occurs, by-products of combustion travel down the chimney, rather than up, and become part of the air breathed by the occupants.

Ground source or air source heat pumps or electric resistance heating are good alternatives to residential combustion furnaces, as is solar heating, either active or passive. Electric space heaters and kitchen ranges are far less polluting than kerosene and gas versions. Commercial HVAC systems, as noted, have their own types of problems, but they too have the potential to supply clean air.

There are many possible pollution sources indoors, but many types of carpeting, man-made wood products and HVAC systems are three of the most important. Simply eliminating these sources would go a long way to reducing indoor pollution in the average building, although it may not always be practical. For very sensitive people, virtually everything in a building should be suspect, and should be tested prior to using indoors.

Roofing materials such as slate and tile are subject to little outgassing as is metal roofing with a baked-on finish. Brick, stone, and metal siding are similarly good choices. In order to eliminate the need for toxic termite treatments, steel framing can be substituted for wood framing, or less toxic treatments like Tim-Bor can be used. However, it is the material used indoors that can contribute the most to poor indoor air quality.

Once a non-toxic flooring has been selected, the floor's finish and the paint on the walls should be considered. Today there are several specialty paint manufacturers that produce less noxious finishes for the chemically sensitive market, however, everyone would benefit from these types of paints, varnishes, and sealants. Some are made in this country and some are imported.

Kitchens, bathrooms and laboratories are the most complicated rooms in a building because of their fixtures, cabinets and appliances. These rooms should be adequately ventilated, and construction and remodeling materials should be chosen carefully. Ceramic tile, stainless steel, metal with baked-on finishes, porcelain, and solid wood are generally good choices. Most commercially produced cabinetry contains a considerable amount of particle board or plywood, yet cabinets constructed of solid wood or metal are available. Many of the cabinets currently being manufactured are sprayed with a very potent formaldehyde based finish. Since much of the drinking water in this country is polluted, a filtration system may be in order, even for municipally supplied water.

After analyzing the many components of a house, it will quickly become apparent that there are some things that can't possibly be eliminated. For these items, the second principle of separation is important. The idea is to separate the offending substance from the living environment. For example, the insulation can often be effectively sealed from the living space by using foil-backed drywall. If outgassing from the plastic jacketing of electrical wiring is offensive, it can be placed inside metal conduit.

Paints and sealants can sometimes be used to seal problematic wallboard or wood trim in order to separate them from the air that we breathe. However, sealants must be carefully chosen in order not to be a problem themselves since many commercially produced products are potentially toxic chemical soups. If construction methods are carefully planned, many offending substances can successfully be separated from the living space with either metal foil or an appropriate sealant. The Airtight Drywall Approach (ADA) is a good method of sealing a building so that the outgassing from the insulation does not reach the living space. Geared primarily to residential and light commercial construction, it is a popular technique in Canada that is beginning to catch on elsewhere.

Last, but by no means least, the principle of ventilation should be considered. To rely on infiltration to supply fresh air in today's tight buildings is foolish because infiltration cannot be controlled. It may be a sufficient source of fresh air on a windy day but less than adequate on a calm day. Since we are living creatures, we constantly need fresh air to breathe. Our bodies aren't content to wait a day or two for the infiltration rate to pick up in order to get fresh air. While it is not commonly done in residences, all modern houses should have mechanically supplied fresh air. The tighter the house, the more important this requirement. Typical construction methods mean that all of the houses being built today should have some form of controlled ventilation. Building with sheet goods, like drywall and plywood, means that there are fewer cracks for fresh air to enter a house. Windows are considerably tighter today than those built in our grandparent's era. The result is that infiltration shouldn't be relied on to supply fresh air to a house. It simply isn't sufficient on most days and it cannot be controlled. Most commercial buildings have some sort of mechanical ventilation system designed to provide the occupants with fresh air. Unfortunately, the design may be inadequate, or the system may be shut down to save on energy costs.

An extremely tight structure can be very desirable from a health standpoint. However, by reducing uncontrolled infiltration to an absolute minimum, ventilation becomes extremely important. This is advantageous to health, in that ventilation can be controlled. It can be turned on and off by the occupants. It can also be filtered. By using a variety of filter types [electrostatic, HEPA (High Efficiency Particle Accumulator),or carbon adsorber], all of the air entering the building can be cleaned. Occasionally, there will be something occurring outdoors that would overload the filtering system. A neighbor applying lawn or garden chemicals or burning trash are typical examples. A spill from a chemical tank truck would be a more serious problem. If there is an outdoor pollution alert, the air supply can be temporarily shut off and the occupants will be protected from the contaminated outdoor air. Of course, the ventilation system should never be shut off for long periods of time in a tightly built structure. Being living creatures, we give off various pollutants as by-products of metabolism such as acetaldehyde, carbon dioxide, carbon monoxide and methane. These can build up, while at the same time oxygen is consumed. As a result, a tight building with the ventilation system shut off for several days can have high levels of pollutants.

Since we can't eliminate many of the outdoor pollution problems, controlled, filtered ventilation may be the only way to insure that the air we bring indoors to breathe is clean. This could be a requirement if the outdoor air is badly polluted on a regular basis.

Although many pollution sources can be eliminated, and others can be separated from the living space, ventilation is still very important. By combining all three principles in new construction or remodeling, a healthful building can be the result. However, it must be remembered that many occupant related activities can easily contaminate the air in a building that otherwise has clean air. For example, smoking, applying pesticides, hobbies, laboratories, shops, kitchens, etc. can require additional ventilation or filtration. Also, many conventional furnishings such as synthetic draperies, couches, desks, copying machines, and office dividers can contribute to poor indoor air quality. Fortunately, there are less toxic alternatives today for virtually everything that is found indoors.


(Note: The views expressed in this article are those of the author, and do not necessarily represent those of The Healthy House Institute, LLC.)


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Principles of Healthy Construction:  Created on October 4th, 2007.  Last Modified on February 28th, 2011


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