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Healthy Home Basics - Interior Walls

By HHI Staff

From The Healthy House Answer Book: Answers to the 133 most commonly asked questions. Questions 88-98.


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88. I’ve heard that plaster is a healthy material. What are its advantages and disadvantages?


You buy plaster as a powder, mix it with water, then apply it to a surface where it hardens. Once completely cured, the plaster is very inert and rock-like. Although most people can’t detect any odor after a few days, a few sensitive people have said that they’re bothered by a slight odor for a month or so.


In the past, 2-3 coats of plaster were commonly applied on top of thin strips of wood lath. In some commercial applications it’s still applied in a similar manner, but it’s usually put over metal lath instead of wood. However, the most common way to use plaster today involves skimming one or two thin coats over a gypsum-board material. The gypsum board has a blue paper face, so it’s usually called blueboard.


Most of the time, plaster walls are painted. For sensitive people who are bothered by paint, plaster has the advantage of being hard, durable, and scrubbable enough that you can actually leave it unpainted. While most plaster is white, it can sometimes be tinted (before its applied) with the same kinds of mineral pigments that bricklayers use in mortar.


As far as drawbacks, plaster is more brittle than drywall and, if it ever cracks, it’ll no longer be airtight. Plaster costs more than drywall, primarily because of the skilled labor required. In some parts of the country, plaster is widely used. But, in other areas, it’s been totally replaced with drywall.


89. What makes drywall different from plaster?


Drywall is a gypsum-board product similar to blueboard. The chief difference has to do with the paper facing. The paper on drywall is a lower-grade paper made from recycled newspaper. Some sensitive people are bothered by printing ink. As a result, they can also be affected by drywall because the paper contains ink residues. This usually isn’t a strong pollutant source, and paint often seals the paper well enough to prevent it from being a problem. Drywall isn’t as durable as plaster, so it can’t be left unpainted.


The other big difference between plaster and drywall is in how they are finished. With plaster, there’s a thin coating over the entire surface of the blueboard. With drywall, a coating of drywall joint compound (often called mud) is applied over paper tape at all the seams and at nail heads—not over the entire surface. The joint compound typically contains a variety of ingredients, such as the minerals gypsum, lime, talc, etc., plus additives such as antifreeze, preservatives, fungicides, and adhesives. These additives can outgas into the living space more than plaster.


We’ve found while plaster is theoretically more inert, sensitive people often tolerate drywall just fine—if they take a few precautions. First of all, because drywall must be painted, you must use a low-tox paint. Second, you should use a low-tox joint compound. The healthiest one we’ve found is the M-100 Hi-Po Compound, made by Murco Wall Products (300 NE 21st St., Ft. Worth, TX 76106, 800-446-7124). It must be ordered from Texas, and is sold in powdered form, so it has be mixed with water on the job. (After the initial mixing, it should set for a while, then remixed to remove any lumps.) Because it contains no preservatives, don’t mix more than you’ll use in a day or it’ll go bad. Once the compound is on the wall and completely dried, most contractors sand it smooth. If you’re concerned about creating sanding dust, it can be smoothed with a damp sponge instead. Murco’s product can also be used for texturing ceilings.


One last note on drywall: The sheets of drywall from different manufacturers are very similar in composition. So, one brand really isn’t any healthier than another. [The exception, of course, is some Chinese drywall.]



90. Why do you use foil-backed drywall in the houses you’ve built?


Foil-backed drywall is just like standard drywall—except that the backside is covered with a thin layer of aluminum foil. While it’s often not kept in stock, it can usually be ordered from any dealer who sells standard drywall. We use it because the foil acts as a diffusion retarder.


We talked earlier about diffusion being insignificant at allowing air or pollutants to travel through solid surfaces. Well, diffusion is insignificant, but it’s also very easy to deal with—so we do. Metals are quite good at retarding diffusion. So, by using foil-backed drywall that’s sealed in an airtight manner, we’re stopping both air movement and retarding diffusion.


We think foil-backed drywall is easy to use, but some builders prefer to use polyethylene sheeting inside the wall. It does basically the same thing, and it’s only slightly less effective as a diffusion retarder than aluminum foil.


91. Should we be concerned about lead paint?


It depends on how old your house is. While the use of lead in paint started to decline about 1950, it wasn’t banned in household paint until 1978. Lead is definitely a pollutant to be concerned about. But, it usually isn’t a problem unless it’s deteriorating, or disturbed during remodeling. So, if your house was built after 1978, and it’s in good shape, there’s a good chance that it doesn’t have a lead paint problem. But, you may want to perform a simple test to make sure. You can buy inexpensive lead-testing kits at many hardware stores.


When it comes to lead—and many other pollutants for that matter—children are at more risk than adults, and children can be natural explorers. So, just because your house is lead paint-free, doesn’t mean your kids are risk-free. They could be exposed to lead at a friend’s house, or outdoors playing near an abandoned gas-station or battery-processing site. So, it can be a good idea for all children to have their blood tested for lead. If you suspect you have a problem, contact your local or state board of health, or call the EPA’s National Lead Information Center at 800-532-3394 for guidance.


92. Can you recommend a healthy spackling compound?


Most typical spackling products have several additives, and they can be odorous. However, if you’re just going to fill a few nail holes, you certainly won’t be using much material. Therefore, a conventional spackling compound probably isn’t going to be a serious outgassing source. For bigger jobs, or if you want to use as safe a product as possible, we recommend the M-100 Hi-Po Compound mentioned above. It works for small jobs as well as large ones. If you’re trying to cover up large cracks, you may want to use some tape (paper or fiberglass-mesh) along with the compound to reinforce it, in order to prevent the cracks from reappearing.


93. What paint should I get for my interior walls?


This is one of our most asked questions, and it’s an important one. There are hundreds—sometimes thousands—of square feet of walls and ceilings in a house. If they’re all painted, that can be a lot of surface area to which you and your family will be exposed. All paints outgas something when they’re wet. Depending on the product, and depending on your degree of sensitivity, the outgassed chemicals could cause a variety of negative health effects.


Some products are definitely stronger than others when they’re applied. And, some take a long time to outgas completely after they’re dry. In general, we prefer water-based paints (and stains and clear finishes) because they outgas less initially, and the outgassing doesn’t last too long. Solvent-based oil paints, on the other hand, are much stronger, and they can take weeks or months until they’re completely cured. They often contain 40-60% solvent, and solvents are nasty chemicals. They often cause symptoms such as dizziness, nausea, and fatigue, and professional painters are more likely to get lung cancer, bladder cancer, and testicular cancer.


Most water-based paints contain a small amount of solvent—usually less than 5%. If you’re not particularly sensitive, any water-based paint will probably be a reasonably good choice. To minimize your exposure, we recommend painting in mild weather when the windows can be left open. You can further reduce your exposure by using one or two window fans. If you want to use a healthier-than-average water-based paint, several major manufacturers (Benjamin Moore, Glidden, Kurfees, and Sherwin-Williams) have introduced zero-solvent (zero-VOC) paints. We still like to apply them with open windows, but they’re very-low odor products, and they’re often well tolerated by sensitive people.


Some very sensitive people have a great deal of trouble finding a tolerable paint. Fortunately, there are several paint companies who make alternative products that are even healthier than the zero-solvent paints distributed nationally. If you want to use one of these paints, you’ll need to plan ahead because they must all be ordered through the mail or Internet. Each manufacturer has a slightly different concept as to what makes a paint healthier. For example, some use all-natural materials, others use synthetic ingredients that outgas very little, and some make paint without preservatives or biocides. We can’t say any one approach is better than another—they’re just different—and none is universally tolerable for all sensitive people. That’s why we recommend that sensitive individuals test several paints for personal tolerance—to see which one is best for them.


94. Is there a healthy interior primer I can use?


Health-wise, water-based primers aren’t a great deal different than water-based paints. But, occasionally we’ve had sensitive people tell us they tested a primer, then tested a paint, and both were tolerable. Then they primed and painted their walls, and were bothered by them. While this isn’t common, it probably involves some kind of reaction between the two different coatings. This situation can be avoided by skipping the primer and simply applying an extra coat of paint.


95. How can I cover a water stain on my ceiling?


This is a case where you must use a specific type of product. That’s because stains can bleed through most water-based paints. What you need is a special stain-blocking primer. There are several on the market. What we generally use is a product called B.I.N. It’s an alcohol-based primer that contains shellac, and it’s widely available. While the alcohol is very odorous, with plenty of ventilation it usually outgases quickly. You really only need to use a stain-blocking primer over the stain itself—you don’t need to prime the entire ceiling. Once the stain has been primed, you can simply paint the ceiling with one of the products discussed above. (Note: in some cases, an alcohol-based primer will react negatively with the Murco joint compound mentioned above.)


96. I have a latex allergy. Is there a healthy paint without latex?


Most water-based paints are called latex paints. However, that doesn’t mean they all contain latex. In the paint industry, the work latex has come to simply mean water-based. In fact, many latex paints contain no latex at all but acrylic, vinyl, or some other resin instead. So, you may tolerate them just fine.


There’s a specially made product that may interest you. It’s a paint made with casein, which is a milk derivative. Manufactured by the Old Fashioned Milk Paint Co. (P.O. Box 222, Groton, MA 01450, 508-448-6336), it’s a powdered material that must be mixed with water. While it’s one of the healthiest paints available, it can have a slight milky odor that might bother someone with milk allergies. And, it has other drawbacks—it can be expensive, it doesn’t cover very well, and it can get moldy in damp locations.


97. Is wallpaper a healthy product?


Today, many wallpapers are made of vinyl or have vinyl coatings, and they can definitely outgas into the living space. Another concern we have is with the glues and pastes used to attach them to the walls. Many contain fungicides so they won’t get moldy. Some fungicides can negatively affect people as well as microbes.


Although we’re not aware of any wallpapers that are healthier than others, we do have a few suggestions. First of all, you can unroll the wallpaper in an uncontaminated garage or in a well-ventilated, unused room to air out until it seems to have lost all its odor. For a paste, consider making your own with white flour and water. To minimize mold problems, you can add about a tablespoon of boric acid powder (usually sold in pharmacies) to each quart of paste.


You might also consider using less wallpaper to reduce your exposure. For example, using a narrow border around a room means less wallpaper, less paste, and less outgassing—plus, less expense.


98. Why is wall paneling unhealthy?


Four-by-eight-foot sheets of wall paneling are made with manufactured wood products that typically contain a potent urea-formaldehyde glue. There aren’t any of these products that are perfect, but those made of hardboard (such as Masonite) are probably the least offensive because they use the least amount of glue.


Personally, our preference is for solid-wood paneling. It can be more expensive, but it contains no formaldehyde-based glue. If you can tolerate softwoods, pine paneling can be reasonably priced. But, there are low-cost hardwoods, too, such as tulip poplar.


If solid-wood paneling looks like it’s going to be too expensive to use in an entire room, you can get a very nice effect by just covering the lower third of the walls with wainscoting. In many cases, a simple horizontal chair rail can dress up a wall at even less cost.


(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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Healthy Home Basics - Interior Walls:  Created on February 3rd, 2008.  Last Modified on February 28th, 2011


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