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General Building    
Posted: November 12, 2014, 12:00am by Scott Allred

Indoor Air Quality

Do you feel like your home is poisoning you? Are you suffering from allergies and other respiratory aliments? Healthy indoor environments attract many people to green building. After energy efficiency, the quality of a home’s indoor air is often cited as the most important feature of green homes.

According to the Environmental Protection Agency (EPA), a growing body of scientific evidence has indicated that the air within homes and other buildings can be more seriously polluted than the outdoor air. In addition, people who may be exposed to indoor air pollutants for the longest periods of time are often those most susceptible to the effects of indoor air pollution. Such groups include the young, the elderly, and the chronically ill, especially those suffering from respiratory or cardiovascular disease.

Green Building Programs, such as the NAHB Green Building Program, requires that measures be implemented to improve indoor air quality in three specific areas:

1. Minimize Sources of Pollutants:
• Low VOC (Volatile Organic Compounds) Building Materials - VOCs are emitted as gasses (also known as “Offgassing”) by many products. Examples include: paints and lacquers, paint strippers, carpet, flooring, plywood, particleboard, adhesives, cabinets, countertops, insulation, paneling, and wallpaper. Formaldehyde, the most common VOC in building materials significantly increases the risk of asthma in young children. Using low VOC building materials is another important step in green construction. Using low VOC building materials has been acknowledged by the industry as a crucial component to any successful project. Next time you start a construction project make sure you ask about the materials you're buying and specify low VOC building materials.
• Proper Ventilation – Poorly designed and installed HVAC systems can lead to comfort and air quality problems. Homes built to provide proper ventilation include outside source combustion air, improved duct and equipment installation, improved filtration, and whole-house and spot ventilation to dilute and remove indoor pollutants.

2. Manage Pollutants Generated in the Home:
• Vent Kitchen Range to Outside – Removes moisture, odors, and combustion gasses that result from cooking.
• Air Filtration - Check, clean, or replace furnace and air filters regularly as recommended.  Consider installing a "high efficiency particulate" MERV 9 or higher filters for better performance.
• Introduce Fresh Air – Today’s energy efficient homes are constructed to be very “tight” to minimize air infiltration. However, to keep the indoor air from becoming stale, plan to introduce outdoor air into the home in a controlled manner through the return duct system or mechanical ventilation devices such as Heat or Energy Recovery Systems (HRV and ERV Systems).
• Radon Control - Exposure to radon, a naturally occurring radioactive, invisible, and odorless gas, is the second leading cause of lung cancer in the United States. In high-risk radon areas, homes should be built with radon-resistant construction techniques. Homebuyers in these areas can also hire professional Home Inspectors to perform radon tests.
• Cleaning - Clean the home regularly to prevent dust, dirt, and pet-hair accumulation. Consider switching to safe cleaning products to avoid emitting dangerous chemicals into the air.  Many products used to clean can release toxic or irritating chemicals when used.  Select cleaning products that are certified for low levels of chemical emissions.

3. Moisture Management: Moisture problems can lead to mold and other biological pollutants that can negatively impact air quality:
• Bathroom Exhaust Fans - Operate the exhaust fan when bathing to limit moisture build up. Consider installing humidistat to control the bathroom exhaust fans and replacing older fans with properly sized higher efficiency models.
• Crawl Space Vapor Barrier – The problem with a crawlspace is that as warm air rises in your home, it brings up with it the air that was previously in your crawl space, including moisture and mold spores, as well as anything else that may be airborne down there. As this air rises in your home, replacement air enters from the lowest part, your crawlspace. This replacement air is made up with unconditioned outside air that enters through vents and other leaks, and air that is actually sucked from the crawlspace floor, either dirt or concrete, which is typically filled with lots of moisture. This natural upward air movement is called the "stack effect" -- this is how chimneys work. Consequently, whatever is in the air at the lowest point eventually flows up into the living sections. Up to 40% of the air we breathe on the first floor of our home comes from the crawl space. To prevent this moisture intrusion, install vapor barrier (8 mil. poly) on the ground in the crawl space and seal holes from the crawl space into the homes floors and walls.
• Protect Building Materials – Prevent the wetting of building materials during construction and check the moisture content before covering on both sides. Use moisture resistant backerboard under tiled surfaces and in wet areas to reduce the risks of water penetrations in kitchens and bathrooms.
• Insulate Ducts and Water Lines – Helps prevent condensation from occurring in the walls and crawl space, epically in hot, humid climates like North Carolina.
• Bulk Moisture - Excessive moisture inside your home usually comes from bulk sources or from condensation. Bulk sources include plumbing leaks and rainwater entering the house through the roof, walls, etc. Deteriorated gutters and downspouts and improper grading of the yard around your house can result in water leakage through the foundation. While bulk moisture sources usually become obvious sooner or later, moisture condensation may go unnoticed for years. Moisture condensation problems can impact home performance by reducing the thermal resistance of insulation, leading to building deterioration by plant and animal pests, possible reducing the life span of the structure of your home; and allowing dust mites, fungus, and mold to thrive – creating a threat to your respiratory health.
Improving your home’s indoor air quality is not always as easy as just opening windows. By incorporating green construction and remodeling practices, homeowners can avoid serious health issues linked to unhealthy indoor air.
Scott Allred is the owner of Precept Construction, LLC and can be reached at scott@preceptconstruction.com or at 336-286-6811.

As this air rises in your home, replacement air enters from the lowest part, your crawlspace. This replacement air is made up with unconditioned outside air that enters through vents and other leaks, and air that is actually sucked from the crawlspace floor, either dirt or concrete, which is typically filled with lots of moisture. This natural upward air movement is called the "stack effect" -- this is how chimneys work. Consequently, whatever is in the air at the lowest point eventually flows up into the living sections. Up to 40% of the air we breathe on the first floor of our home comes from the crawl space.
A concrete or dirt crawl space with a crawl space vent is a never-ending source of moisture. Even if the dirt's surface seems dry, digging down a few inches reveals moist earth. 


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