Tips for Building a Healthy Home – Radon and Combustion Gases
Tips for Building a Healthy Home
If you are building a new home or significantly remodeling your existing home, then this article will help you target the biggest polluters in your home’s indoor environment. These tips for building a healthy home have been put together with the intent of helping those who do not have a healthy materials/green consultant on their team, so they can be aware of and know what to watch out for.
Radon is a natural, radioactive gas that can enter buildings through slab floors and basement walls, as well as from certain masonry materials used in the building itself. Relative to human health, radon is considered the second greatest cause of lung cancer in the U.S., behind tobacco smoking, but there is considerable debate as to how bad radon really is. Here is what the EPA has to say about Radon. This scientific debate aside, radon control and mitigation measures are fairly easy to incorporate into buildings and should be done as a precaution. Typical measures include providing clean, uniform-sized aggregate under the basement or first-floor slab, providing a layer of polyethylene under the slab, and installing a capped pipe through the slab that can be uncapped and extended up and out through the building ( with an in-line fan to ventilate radon if testing shows levels to be unacceptably high).
Combustion gases are considered by many experts to be among the most harmful contaminants in indoor air, but they are also among the easiest IAQ problems to solve. The primary products of natural gas combustion are carbon dioxide and water vapor—shown for methane (the primary constituent of natural gas) as follows:
CH4 + 2O2 = CO2 + 2H2O
In reality, however, combustion is seldom so simple. If oxygen levels are inadequate, some carbon monoxide (CO), a poisonous gas, will be produced in place of some of the CO2. Also, some atmospheric nitrogen is typically combusted to form nitrogen dioxide (NO2), and small quantities of other nitrogen oxides, sulfur dioxide, formaldehyde, and various tar-like substances. Fortunately, it is fairly easy to eliminate combustion gases from buildings. This means installing only combustion products with active venting directly to the outdoors. For furnaces, water heaters and gas-fired room heaters, the best option is sealed combustion, in which outside air is brought directly into the combustion chamber and exhaust gases are vented directly to the outside, with no opportunity for interaction with the indoor air. The second-best option is direct-vent or power-vented equipment, in which indoor air is used for combustion, but a fan forces exhaust gases to the outside. Natural-draft combustion equipment, in which the warm gases rise up a chimney or flue due to their natural buoyancy, should be avoided.
Eliminate the Fireplace
Gas fireplaces are installed in homes mainly for decorative purposes. Having no fireplace is the best way to reduce the risk associated with leakage of exhaust combustion gases into the house. Even factory built fireplaces and stoves with tight fitting doors can result in some back-drafting of combustion gases into the house. The greatest risk comes from running large exhaust fans (like the kitchen range hood) which can depressurize the home and pull air from the fireplace back inside.
Radon & Combustible Gases is part of a series of blogs on Tips for Building a Healthy Home.
Who is Healthy Building Science?
Environmental Testing Services at HBS
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