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From The Healthy House Answer Book: Answers to the 133 most commonly asked questions. Questions 30-39.
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30. We’re considering building a house with steel framing. Does it have any particular advantages?
Light-weight steel framing is becoming popular with some builders. It consists of C-shaped studs and channels that are usually lighter-in-weight than wood. Everything is held together with self-tapping screws, and the studs typically have holes prepunched in them for electrical wires and plumbing lines. This saves drilling time, but the holes have sharp edges, so they must be fitted with plastic grommets to prevent plastic-jacketed wiring from getting nicked and shorting out. Steel framing is also very uniform in size, it has no knots, and it won’t warp.
The biggest health-related advantage to steel is the fact that it never needs to be treated for termites. So, where toxic chemical use is the norm, or where less-toxic alternative treatments aren’t feasible, steel is a great option.
Although it’s not a concern for most people, some very sensitive individuals are bothered by the natural odor of wood, and steel is odor-free. Most framing lumber is pine or another softwood, and the odor is composed of the same chemicals in turpentine. These sensitive people are just reacting to much lower levels of the same pollutants that have the potential to bother all of us.
While steel itself usually doesn’t have an odor, it sometimes has a slightly odorous oil film on it left over from the manufacturing process that some sensitive people have had to wash off. A solution of water and TSP (tri-sodium phosphate, a heavy-duty cleaner often available in hardware stores) usually works well.
31. Are there any disadvantages to using steel framing?
The biggest disadvantage to building with steel has to do with the fact that steel is an excellent conductor of heat. An insulated steel-framed wall can be very energy inefficient. For example, there can be so much heat loss through steel studs, that the average insulating ability of the wall is degraded by up to 50%. This can be a serious drawback—especially in harsh climates—but there are some ways to minimize energy losses. For example, you can space the studs further apart. Fewer studs equals less heat loss.
Most residential builders have never worked with steel, so they don’t really understand some of the unique details that go into a steel-framed house. While the actual cost of the material is often comparable to wood framing, if a contractor is unfamiliar with steel, he may charge more for labor.
There are a few specialized tools required—a screw gun, a cut-off saw fitted with a steel-cutting blade, some tin snips, and perhaps a crimping tool. Plus, you’ll need a selection of self-tapping screws—they come in dozens of sizes and shapes.
32. Does it matter what kind of sheathing we use on our house?
There are negative health affects related to most sheathing materials. For example, there are several different kinds of foam boards that are relatively odorless. However, some release chemicals that can damage the Earth’s protective ozone layer. In a fire, foam sheathing gives off very toxic gases. Asphalt-impregnated fiberboard sheathing has a slight asphalt odor. Gypsum-board sheathing has a facing paper that’s chemically treated, and plywood and oriented-strand board contain formaldehyde-based glue.
The good news is that health effects related to sheathing usually aren’t significant. One of the reasons is because materials outside the living space don’t tend to have a serious affect on indoor air quality. Actually, the sheathing is inside the wall cavity—sandwiched between the siding and the interior wallboard—so it can’t outgas inward or outward very easily.
Still, sheathing can bother some very sensitive people. For them, the solution may mean eliminating sheathing. This is possible, but you must analyze the situation carefully—and make sure you don’t violate any building codes. If you build a house as airtight as possible, the materials inside wall cavities are almost never a health problem.
33. Do you think housewrap is needed on my new house?
Housewrap is a plastic fabric-like material sold in wide rolls. It’s designed to be stapled over the exterior sheathing of a home and act as a wind barrier. By preventing the wind from blowing through the cracks, it can improve the energy efficiency of a house. Most brands have little odor. And, as with sheathing, housewrap is always covered up with siding, so you’re not exposed to it directly.
Some very sensitive people have used an aluminum-foil-faced Kraft paper, called builders foil or reflective insulation, as house wrap. Plastic housewrap is manufactured so, in cold climates, moisture will pass through it, rather than become trapped inside the wall cavity. So if you opt for builder’s foil in a cold climate, you should get the type that has tiny pin pricks in it. This perforated product will still block the wind, but it won’t trap water vapor. One supplier of builders foil is E.L. Foust Co. (P.O. Box 105, Elmhurst, IL 60126, 800-225-9549).
34. What does the term R-value refer to?
When you buy insulation, it will have an R-value such as R-13 or R-38. This is a measure of how well a material resists the flow of heat, so the higher the number, the better its insulating ability. However, there’s more to heat loss than R-value. For example, a house can have walls filled with plenty of insulation having a high R-valve, yet be costly to heat or cool. This is usually because the house is leaky, and there’s a significant amount of air moving through those leaks. Leaking air can carry a great deal of conditioned air with it. So, making a house energy efficient takes a combination of R-value and tightening.
35. What options do I have for insulation?
The bad news is, there are negative health effects associated will all insulations. The good news is, in most cases, we’ve found insulation stays inside building cavities where it's been placed, and usually doesn’t affect the indoor air quality. Of course, there are horror stories where insulation has been responsible for very serious health problems. Therefore, it pays to select and install it with care.
In the 1970s, a product called urea-formaldehyde foam insulation was in use that was capable of releasing a great deal of formaldehyde. It hasn’t been around for some time, but there are a number of other foams on the market today. Some are sold primarily in 4' x 8' sheets, while others require special equipment to foam them in place inside walls, floors, and roofs. Once cured, there isn’t a great deal of outgassing from any of these newer foams—but there is a little. And, many can give off toxic gases when they burn. As a result, most building codes require that they be covered with something such as drywall. Once covered up, they’re never directly exposed to the living space.
Fiberglass is one of the most widely-used residential insulations. It can be unhealthy for two reasons. There is some evidence that tiny glass fibers, when they’re inhaled, can lodge in the lungs and possibly result in illness. In addition, most fiberglass insulation is held together with a formaldehyde-based resin. The resin isn’t a strong outgasser, but it can bother sensitive people.
Cellulose insulation is made from ground-up newspapers. It’s very dusty and can be contaminated with printing ink, mold, and flame-retardant chemicals. Cellulose is often installed in existing walls by blowing (injecting) it under pressure through small holes drilled in the siding (or through the interior wallboard). When this is done, a certain amount of insulation can be blown into the living space. (Chopped fiberglass can also be installed in this way.) In new construction, cellulose insulation is sometimes mixed with a tiny amount of glue or water and sprayed into wall cavities before they’re covered with drywall. In all applications, once installed, the insulation is outside the living space.
Cotton insulation is also available. It’s billed as being more environmentally responsible because it’s made from recycled cotton jeans—and cotton is a renewable crop. However, it isn’t perfect. It must be hand-fluffed to reach its full thickness. And it isn’t 100%-cotton—it contains some polyester and is treated with a boric-acid flame retardant.
There are other materials that can be used for insulation, such as cork, feathers, straw, etc. All have advantages and disadvantages. The perfect insulation simply doesn’t exist.
36. So, what’s the healthiest insulation to use in my house?
This is one of our most often asked questions. While the residential insulations in common use all have drawbacks, they've all been used in healthy construction. In fact, wherever there have been serious health problems associated with insulation, it’s usually resulted from exposures during installation or remodeling when the insulation is being disturbed. It’s been our experience that if you’re concerned about your health, it’s much more important how the insulation is installed, than which product is used.
If you have an existing house and you want to add some insulation, it should be done with care. This is because, the installation process itself often contaminates the interior of the house. This is particularly true if cellulose or fiberglass is blown into building cavities. In most cases, there will be bits of fiberglass or cellulose floating around indoors, and perhaps small piles of insulation on the floor near electrical receptacles or light switches. In some cases, heating ducts have been inadvertently filled with insulation, or insulation has been sucked into leaky ducts. We recommend, during the actual insulating process, a workman be indoors to make sure there are no significant amounts of insulation filtering into the living space. Then, after the job is finished, the interior should be cleaned up thoroughly. In most cases, the insulation will be packed fairly tightly inside the walls—and it will probably stay there. However, some could filter into the living space later, from the walls or attic. If this happens, you should determine where it's entering and caulk, or otherwise seal the pathways. (Be sure to check for leaky ducts.) Once that’s been done, the insulation probably will no longer pose problems.
In new construction we recommend that the house be built as tightly as possible. That way, whatever insulation you choose, it will be very well separated from the living space. If it can’t get into the air you breathe, then it can’t affect your health.
37. I thought tight houses caused indoor air pollution. Why are you saying they’re a good idea?
The people who claim that tight houses are a problem don’t understand the whole picture. As far as indoor air quality is concerned, the unhealthiest houses are those built with polluting materials and having no mechanical ventilation. These houses often have a problem no matter how loose they are. However, the indoor air quality is worse, if they’re tightly built. By the way, loose houses also have other disadvantages. They’re often expensive to heat and cool, too dry in the winter, drafty, and uncomfortable.
The healthiest houses are actually built as tight as possible—using both healthy materials and a mechanical ventilation system. This results in a number of advantages. For example, a tight house is more energy efficient, and quieter. It’s less likely to develop hidden moisture problems inside building cavities. Pollutants in the soil (such as radon and termite chemicals) can’t enter it easily. Pollutants inside the building cavities, such as insulation (or the slight odor of pine framing), can’t enter it easily either. Because healthy materials were chosen, there aren’t any significant pollution sources indoors causing problems. The mechanical ventilation system provides the correct amount of ventilation at all times—neither too much to be wasteful, nor too little. And, finally, if there is an outdoor pollution alert (say, a neighbor is spraying nasty chemicals on his fruit trees), the air coming in through the ventilation system can be filtered. The entire ventilation system can even be temporarily turned off. With loose construction you have no such control.
There are several techniques and materials that can be used to tighten a house. We’ve used gaskets, caulking, aerosol-foam insulation, and air-tight electrical boxes. The goal is to seal all the many cracks and gaps that can be found between all the different building materials. The Energy Efficient Building Association (2950 Metro Dr. #108, Minneapolis, MN 55425, 612-851-9940) offers books on tight construction techniques. John Bower's Healthy House Building book shows how to build an airtight healthy house in a step-by-step manner.
38. What’s a vapor barrier and should I use one?
A vapor barrier is more correctly called a diffusion retarder. That’s because most materials aren't really perfect barriers, so retarder is a more accurate term. Plus, they tend to retard not only vapors but gases as well that are moving through materials by a process called diffusion.
There’s often some confusion between airtight and diffusion-tight. In airtight construction, you seal up all the small holes and pathways that air can move through due to differing air-pressures. For example, when the wind blows on the side of a typical house, it pushes air, and airborne pollutants, through the cracks and gaps. But, with airtight construction, there aren't unplanned cracks and gaps. As a result, the wind can’t push any air or pollutants through to the interior living space.
On the other hand, diffusion-tight means greatly reducing the movement of gases and vapors (not particles) through a solid surface. The speed with which they pass through a material depends on their concentration in the air, and on the material’s composition. Diffusion is faster through cardboard and drywall than through glass and metal.
If you study the laws of physics that apply, you’ll see that in most houses, 100 times more air (with or without pollutants) is traveling through the tiny gaps and cracks than is moving by diffusion through all the solid surfaces combined! So, if you plug up the holes by making a house airtight, you’ve stopped 99% of the air and pollutant movement. As it turns out, in most cases, diffusion isn’t very significant.
There are a variety of products that retard diffusion quite well. Plastic sheeting is widely used, but the asphalt-impregnated paper on fiberglass insulation also works well. Aluminum foil, glass, glazed ceramic tile, and some paints also function as diffusion retarders. While some of these materials are slightly better at retarding diffusion than others, the differences are small. And, because diffusion isn’t an important way for pollutants or moisture to move through surfaces, in practice, all work acceptably. Diffusion retarders are a good idea, easy to install, and widely used. However, they generally aren't as important as sealing up the cracks.
39. I’m bothered by the odors of both pine framing lumber and fiberglass insulation. If I build an airtight house, can I use them inside the walls?
You sure can. If there’s an airtight wall between you and the pine framing and the insulation, you should be just fine. In fact, Lynn’s bothered by those same materials, too, and we built our own house with them. Once everything was sealed, she could no longer smell them indoors.
The interior partition walls between rooms usually aren’t insulated, and it generally doesn’t make sense to make them airtight. Therefore, for pine-sensitive people, we like to use light-gauge steel studs for partition walls. That way, there’s no pine odor within the airtight envelope.
(Note: This article is part of the original HHI Archives, and was believed to be accurate at the time of writing. 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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