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If you are planning any serious remodeling, such as adding a room addition to your house, there are several environmental factors to consider. Two basic ways of analyzing the environmental impact of construction materials: 1) are they healthy for the planet? and 2) are they healthy for people? Of course, these two issues aren't mutually exclusive. For example, if the planet's health is damaged, then people will suffer the consequences. On the other hand, planetary health loses its immediate importance to someone who is made ill because they chose the wrong building products.
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When selecting construction or remodeling materials it would be nice if we had products to chose from that were benign from both a planetary and a human health standpoint. However, in our complex industrialized society, our choices are rarely simple, so we must usually make compromises. This article will discuss the various ways in which windows affect our environment.
For hypersensitive individuals, windows are not usually a major consideration. At least they do not have the same degree of negative impact on indoor air quality as significant polluters like particle board. However, there are several factors to consider. For example, a window frame can outgas a variety of pollutants into the air, depending on what kind of material it is made of. Also, rubber and plastic seals can bother some people, but they usually aren't as bad as the more odorous glazing putty. Finally, if a window requires periodic painting, the occupants will be exposed to various volatile gases until the paint fully cures.
From the standpoint of planetary health, a window should be made of materials that are renewable, materials that do not result in environmental pollution during their manufacture, or materials that to not consume a great deal of energy to produce.
Energy efficient windows are important because, by helping to lower heating and air conditioning bills, they reduce our overall dependence on energy. Also, an airtight window will result in less infiltration, therefore when it is shut outdoor pollution can be more easily kept out of the living space. While it is certainly possible to find cheaply made loose fitting windows, most of the windows being made today are far tighter than the ones our grandparents had to put up with. (An important point to keep in mind is the fact that the tighter the house, the more important a mechanical ventilation system becomes. I feel that all modern houses are tight enough to require such systems.)
Vinyl window frames are quite popular today, but they also have a fairly negative impact on the environment. Most plastic materials are made from petroleum or natural gas, both non-renewable resources. We recently fought a war in the Mid-East over, among other things, petroleum. That war resulted in tremendous environmental damage, not to mention loss of human life. All around the world, oil spills have polluted beaches, and natural gas pipelines disrupt the countryside.
Plastics can also affect human health. Chemically sensitive people may have an intolerance to synthetic odors given off by plastics. This is called outgassing and it is one of the causes of indoor air pollution. Outgassing will be more pronounced when a plastic window frame is heated up by sunlight, but it should decrease as a window ages.
When plastics are burned, they emit dozens of extremely toxic gases such as phosgene (nerve gas) and hydrogen cyanide (used in gas chambers). It is no wonder that fire fighters routinely wear protective breathing gear. On the plus side, vinyl window frames are often lower in price than the alternatives, they usually aren't subject to mold growth, and they require no periodic painting.
Wood framed windows are also quite common, and wood is a renewable resource. However, some logging practices, like harvesting old growth forests, destroying habitat, and creating single species tree farms are far from benign. But a wood window frame can be quite attractive.
Most wood window frames are treated with small amounts of biocides, some of which are fairly noxious chemicals, to reduce their chances of being attacked by mold, mildew, or insects. A lesser concern is the fact that most wood windows are made of softwood lumber, like pine or fir, woods that some sensitive people react to because of the natural occurring terpenes (turpentine-like compounds) contained in the wood. Once the window frames have been sealed with a tolerable paint, and the paint has cured, wood windows are often fairly inert. However, for hypersensitive individuals concerned that the biocides and terpenes might not be sufficiently sealed, metal frames might be a better choice.
Aluminum window frames are quite benign from an outgassing standpoint, however the manufacturing of aluminum is a very energy intensive process. Recycling your beer and pop cans can help reduce this problem because it takes far less energy to reprocess aluminum than it does to produce it from scratch. Fortunately, a high percentage of aluminum is already being recycled today.
Some aluminum windows frames "sweat" in the winter, leading to mold growth. With millions of people allergic to mold, this isn't a good thing to have happen, and if the mold spreads to the wood structure of the house, it can result in rot. Aluminum window frames with thermal breaks will eliminate this problem. They are actually made of two separate frames, an inner frame and an outer frame, fused together with a material that will not conduct heat.
In most climates in the United States, windows should have multiple glazing because the trapped air in the space between the panes reduces heat loss in winter and heat gain in the summer. Two thin air spaces insulate better than one thicker space. A low E coating (E, short for emissivity, refers to the ability to reflect or absorb radiant energy) can save as much energy as an extra pane of glass. Low E coatings are composed of benign, microscopically thin (and virtually invisible) metallic films on the glass. Besides saving energy, low E coatings also block the transmission of the ultraviolet portion of sunlight that can cause fabrics to fade or deteriorate.
Some windows contain plastic films between the panes rather than extra pieces of glass. The films can increase energy efficiency because they form multiple air spaces, and the plastic is sealed well enough so that it shouldn't pose a problem from an outgassing standpoint. The plastic films are used because they are lighter in weight than glass and they can have a low E coating applied to them.
A few manufacturers are filling the space between the window panes with argon because it will reduce heat loss when compared to an air filled window. As long as the argon remains in the window, it should cause no problems. However, even if it did leak out, it is doubtful if it would have a negative affect on either people or the planet because argon is chemically inert and naturally occurring in the atmosphere.
Sometimes polycarbonate or acrylic (Plexiglas is a popular brand name) plastic is used instead of glass in doors or other locations where there is an increased danger of injury from breakage. Someone hypersensitive to outgassing from plastics may wish to substitute safety glass. It is more costly, but not subject to outgassing.
What kind of windows do I use in the healthy houses that I build? I consider occupant health first, but I also consider planetary health, so I use triple glazed aluminum windows with energy efficient thermal breaks in the frames. They seem to be the most inert for sensitive people, therefore I feel that they are the healthiest choice for those of us in optimum health. My houses are also superinsulated so they have very low heating and air conditioning requirements. Over their lifetime these houses should save more energy than was consumed to process the aluminum window frames in the first place. If all houses were built this way, it would mean fewer emissions from power plants and better health for us and our planet.
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