We should first practice source control. The idea is to avoid introducing contaminants into your home in the first place. Any efforts here will significantly reduce both your indoor air quality issues and the efforts and the expense that you would otherwise incur attempting to remediate them. This sounds obvious, but on how many projects does the builder spend even ten minutes considering these issues? The sad answer is very few, unless you make it a point to discuss this issue and insist it be a consideration. We now understand that our homes, like our commercial buildings, must be properly ventilated to control the buildup of toxic chemical compounds and particulates. When we ventilate, we dilute these potentially damaging contaminants and restore a healthy environment in our homes. Building science research has a mantra you may want to remember: “Build the home tight, but ventilate it right.”
Many product labels contain cautionary instructions for wearing safety apparatus while applying the product and proper ventilation of the space, but do not give you any indication of the time frame of off-gassing that might affect the health of your family. To minimize our exposure to harmful VOCs, we need to become more educated on the different types of common products used in home construction, as well as those used to maintain the home over its lifetime. VOCs can be reduced or eliminated from interior finish products by specifying products that are tested and certified to be within acceptable limits.
You should also look for interior finish products that contain no heavy metals, phthalates or aromatic solvents. It would be wise to reference a known and respected source, like Green Seal, with the professional staff needed to evaluate MSDS sheets and provide you with acceptable standards specifications for various types of materials, the guidance that you will need to make the right choices. Even better are products made from natural ingredients with less environmental burden associated with their life cycle, that are durable, with ease of maintenance, and do not require toxic cleaners.
Materials Finished Offsite
Whenever possible, choose products like cabinetry and flooring that are prefinished before they are delivered to your jobsite, or have been finished offsite. This allows the initial blast of high-VOC off-gassing to occur before the product is ever introduced into your living space, where continued release of toxic fumes will be less. This, of course, is not true if the product has then been wrapped in plastic to keep its moisture content stable or to protect that new finish. If this is the case, it’s best to remove the plastic wrapping and leave the materials in an open-air garage or storage space for a day or two before installing them. Of course, the amount of off-gassing varies, depending on the type of product, so some products will still release VOCs for years even if they came prefinished, like engineered wood floors or cabinetry. Again, you can request MSDS reports on these products, as they are required to provide information on the chemicals used in these processes.
Materials That Require Less Finishing
As mentioned in Equipment & Systems Category, selecting materials that require less finishing can save resources and reduce maintenance, thereby reducing costs both initially and over time. However, perhaps the most important contribution of less finishing is less off-gassing of toxins associated with finish products. Natural wood and stone products, as well as tile and concrete, can be used without toxic finish applications or with natural finishes that are durable and have a long life expectancy.
Radon
The Environmental Protection Agency (EPA) recognizes that “radon is a cancer-causing, radioactive gas…that is estimated to cause thousands of deaths each year…the second leading cause of lung cancer.” If your home is to be located in an area recognized as a radon hazard zone, you should take the appropriate steps to properly vent and reduce the risk of exposure to occupants within the structure (see Chapter 4). Other odorless soil gases, such as methane, may also be a concern and should be addressed through appropriate detection devices.
Garages
Many homes have attached garages that contain bags of chemical fertilizers and pesticides, volatile gas fuels stored in poorly sealed containers, automotive exhaust fumes, paints and varnishes and other toxic products. Every time we open the door from the garage to the house, we allow some of these fumes in. Even with the door closed, the wall separating the house and garage is typically two and a half times leakier than other exterior building walls. Why? Homebuilders don’t see this as an outside wall, so they don’t take the time to effectively air seal it. Make certain this detail is addressed if you are building or remodeling this area of your home.
We recommend moving all chemicals, fuels, fertilizers and pesticides from your attached garage into a detached garden shed. And never start your car with the garage door closed. Installing an exhaust fan in the garage that is tied to the garage door opener and runs for a few minutes after the car has exited and the door has closed is also a good idea. The US EPA has made some recommendations about how this could be achieved at their website.
Laundry Rooms
Laundry rooms are major sources of heat and moisture (breeding dust mites, mildew and molds). They should be equipped with an exhaust fan, vented to the outdoors. These fans should have a sensor to activate operation automatically and run until the sensor detects that the desired level of moisture reduction has been achieved. Clothes dryers contribute to negative air pressure in the home, exhausting large volumes of air that must be made up from somewhere, which usually means from places that you would prefer not to draw air from. The best case would be to locate the laundry area outside of the conditioned space. Installing a clothes line will also contribute to reducing these laundry room issues.
Combustion Appliances
Gas combustion appliances, including furnaces, water heaters, fireplaces and cooktops release toxic gasses (carbon monoxide, carbon dioxide, sulfur dioxide) every time they are ignited. Standard, open-combustion appliances are not sealed well enough to prevent backdrafting from the combustion gases in the vent pipe in the event that negative pressure occurs in the home. This can happen anytime the clothes dryer, fireplace or exhaust fans are in operation. In a tightly sealed home always buy sealed combustion gas appliances and always use proper exhaust spot ventilation when operating gas cooktops.
Fireplaces
Indoor gas, pellet and wood-burning appliances and fireplaces also release toxic fumes into the living space. EPA researchers suggest that exposure to wood-burning appliance emissions presents a greater cancer risk than exposure to the same amount of cigarette smoke. Additionally, the fine particulates in the smoke emitted from chimneys is the largest single source of air pollutants for neighboring homes. The worst offender is the ventless gas-fired fireplace, which have been outlawed in a number of states and countries. Even though these appliances claim to be 100 percent efficient, as their name implies they have no means of exhausting to the outside the combustion gases and particulate pollutants generated by their operation. All of those gases and particulates are sent directly into the living space. Additionally, these appliances generate a lot of moisture, which can further impact indoor air quality, leading to mold, mildew and related health concerns. You should never install an unvented fireplace inside your home, due to the high risk of contaminating your air or causing damage to your family’s health or even death. In fact, it is better not to have any type of fireplace or wood-burning stove installed indoors on a porch or patio, unless it is EPA-certified as meeting required safety standards. Direct-vent fireplaces work the best to manage smoke and combustion gases and take them out of harm’s way.
It is also important that fireplace appliances have a dedicated source for outside combustion air, so that they are not pulling conditioned air out of the living space to create the fire and then exhausting that air up the chimney. If you have an existing fireplace and would like to make it as safe as possible, make sure it has an air vent and then install sealed glass doors, so it can be operated with the doors closed.
Fresh Air Systems
Introducing supplemental fresh air ventilation to increase air exchanges also improves indoor air quality by diluting the level of contaminants caused by off-gassing, soil gas infiltration or infiltration of toxic fumes from all of the sources that we have discussed. Because high- performance building systems provide typically tighter construction than traditionally built homes, they do not allow the recommended quantity of fresh air to infiltrate the envelope. Mechanical fresh air systems not only provide a calculated amount of fresh air into the home, but also should provide some filtration of the air through the conditioned air system, so allergens and pollutants introduced to the space are minimized.
Filtration
Air filtering is also a good front-line defense for protecting the mechanical equipment from contamination, although not so much for improving the quality of indoor air. Although many filters manufactured today remove some percentage of dust, pollen, dust mites and other contaminants, the truth is that they do not manage the turnover of air within your entire space well enough to keep the air particle-free. Some return air grilles are located on walls near the floor, while others may be located high on walls or on ceilings. Some are in areas of the home far away from the main sources of pollutants (like in hallways, far from exterior doors, moisture sources or garages). Many spores and pollen grains fall quickly to the carpet only to be stirred up every time you walk through the room. To think that filters can be effective in cleaning our air is not realistic.
High-efficiency particulate air (HEPA) filters meet the standards of efficiency set by the Department of Energy (DOE) by removing at least 99.97 percent of all particles greater than 0.3 microns from the air that passes through filtrations systems. The key to improving indoor air quality is to have these systems ducted so that they are able to continuously circulate the large volume of air within the conditioned space, which is not an easy task. Additionally, these filters only remove airborne particulates, so they are not effective in removing heavier particulate matter that settles out, or at cleaning the air of toxic fumes off-gassed by indoor pollutants. Return air grille location high on walls or on ceilings is very effective at reducing particulate matter contamination of ductwork, since gravity will keep most of that below the intake zone. It is important to note that filtration does nothing to reduce the volume of toxic vapors caused by the off-gassing of chemicals in building materials.
The best means of addressing good indoor air quality is to exchange fresh air with stale air. But it is a good idea to use good filtration and do the best that you can to protect your system from premature contamination problems, and also to do what you can to remove dust and pollutants from the air. At minimum, pleated media filters should be used at all return air grilles. Filters with a rating of MERV 8 fit this basic requirement. MERV 10 is better and MERV 13 is best, as long as your HVAC system fan is rated for the restricted airflow of these filters caused by their design. Many residential furnace/air conditioner fans are not powerful enough to pull air through the thicker or more efficient filters without suffering premature failure. IF you intend to use a MERV 10 or higher filter, you should inform your HVAC contractor so they can determine if the fan in the system they are installing is compatible. Change filters at least according to the equipment manufacturer’s recommendation or more frequently if your family’s lifestyle and health concerns require it.
