For more on our 15-part Q&A series on all aspects of green building, click here for the introductory post.
Question: Have houses always been unhealthy or this something new?
Answer: Over the centuries, many houses have been unhealthy due to mold, wood smoke, gas lighting, kerosene heaters, coal dust, pests, animal dander, lead pipes, lead paint, asbestos, etc. While some of these pollutants are less common today, we now have new pollutants such as formaldehyde with which to contend. So, although unhealthy houses have been around for a while, the specific pollutants are changing.
Question: With all the new environmental laws and regulations, why aren’t houses healthier than ever before?
Answer: In some areas, there definitely has been some progress. For example, we no longer use lead paint or asbestos insulation. But in many instances, we’re creating new building products and developing new construction practices faster than they can be evaluated or regulated. Today’s indoor environmental pollution problems are related to two trends—the use of unhealthy materials and unhealthy techniques.
Question: What are the two trends that are contributing to make today’s houses unhealthy?
Answer: First of all, we’re now building houses tighter for greater energy efficiency, but without mechanical ventilation systems. And second, we’re filling these tighter houses with synthetic, man-made building materials, furnishings, and cleaning products—many of which release pollutants into the air. So, we end up with pollution-filled houses that don’t have enough fresh air. The result is often ill health.
Question: How bad is the air in a typical home?
Answer: According to many studies, the air inside most houses is 5 to 10 times worse than the outdoor air. And it doesn’t matter where you live—in a major city, or in a rural area—the air is almost always worse indoors. If you measure individual pollutants, some are a whopping 100 times worse indoors.
Question: What are the types of contaminants that are often found indoors?
Answer: We usually put them into six categories:
1) Biologicals (pollutants that are, or once were, alive) such as mold, mildew, pollen, dust mites, animal dander, bacteria, and viruses.
2) Gases resulting from human and pet metabolism (ammonia, certain alcohols, carbon dioxide, methane, etc.), gases that are by-products of combustion (carbon dioxide, carbon monoxide, sulfur dioxide, etc.), and gases that are released by synthetic and man-made products (formaldehyde, hexane, toluene, etc.).
3) Metals such as lead (which used to be popular in paint), mercury (once used as a fungicide in paint and drywall compound), arsenic and chromium (widely used in chemically treated lumber).
4) Minerals such as asbestos (found in some older insulation, vinyl tiles, and drywall compounds), mineral fibers and particles from fiberglass insulation, and air-borne minerals spewed out of humidifiers from tap water.
5) Radiation from naturally occurring radon, electromagnetic radiation from wiring and electrical appliances, and radioactive waste in some smoke detectors and compact-fluorescent lamps.
6) Vapors, which in most houses means too much water vapor, something that can lead pollutant problems such as mold growth—or rot.
Question: What are VOCs and could they be big polluters in my home?
Answer: VOC stands for volatile organic compound. There are hundreds of different VOCs and they have two things in common—they contain carbon, and they evaporate quickly. Some are natural and relatively benign—baking bread and cutting onions releases VOCs. But other VOCs are synthetic and aren’t so safe to be around. They can be released by paints, solvents, caulking, and adhesives. Formaldehyde is probably the most recognized VOC. It’s widely used in plywood, particle board, finishes, and many other products. Some VOCs are irritants, carcinogens, and mutagens. They can be serious indoor polluters.
Question: What is outgassing?
Answer: Outgassing refers to release of VOCs as a material ages or degrades. New-car smell is composed of various gases that are released from the synthetic materials making up a new automobile’s interior. As it turns out, many common building materials (cabinets, paneling, paints, etc.) outgas harmful VOCs.
Question: I’m fairly certain my house is making me sick. Should I hire a company to test the indoor air?
Answer: If you feel better when you’re away from home, then get sick when you return, your house could indeed be making you sick. In some cases, professional air-quality testing can be helpful to understand why. But there are hundreds of possible pollutants, and testing for them all can cost hundreds, or thousands, of dollars. If you do such testing, you’ll probably be given a list of perhaps a hundred pollutants unique to your house. Because there are so many pollutants that haven’t been studied, you’ll know what you’ve got, but you won’t know what it means.
For the pollutants that have been studied, the guidelines as to what constitutes a safe exposure were often established for healthy workers in occupational settings. If you’re hypersensitive, you could easily be bothered by much lower levels—levels many experts consider safe.
A little detective work on your part will often provide more useful information than air-quality testing. For example, ask yourself when your symptoms started. If it was after some remodeling, you should suspect the building materials. If it was after a new furnace was installed, your problem could be related to a fuel leak, combustion by-products, leaky ducts, or the materials the ducts are made of. If your house was recently weatherized, it may have been tightened to the point it no longer has enough fresh air, or the indoor air could have been contaminated with insulation. If you’ve had a flood, you should suspect mold. If you just built a new house, there can be a number of possibilities—outgassing from new materials, lack of ventilation, heating/cooling system problems, etc.
Question: I’ve heard of something called a bakeout. Won’t that increase the outgassing rate and get rid of the VOCs in my house?
Answer: A bakeout seems like the perfect solution. It involves heating a building up to about 95°F for three days or so, while simultaneously airing it out with window fans. This is a simple solution to a complex problem, and it doesn’t always help. In fact, some studies have shown that the levels of some pollutants can actually increase after a bakeout.
Question: How long does it take for a typical house to air out on its own?
Answer: This is a difficult question to answer because there are so many variables. For example, different brands of similar products outgas at different rates, the rate changes at different temperatures and humidities, and natural (or mechanical) ventilation is a factor. Plus each different VOC has its own particular outgassing characteristics. As an example, formaldehyde (which is commonly used in kitchen cabinets and wall paneling) typically has a half-life of 3 to 5 years. So, these products will only lose half their formaldehyde in that time. And it’ll take another 3 to 5 years for half of the remaining formaldehyde to be released, and so on. Because outgassing decreases with time, older houses often have lower levels of VOCs than new houses—if they’ve been maintained with healthy cleaning products and there’s been no recent remodeling.
(Note: This article is part of the original HHI Archives, and was believed to be accurate at the time of writing.)
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