Keeping your home adequately sealed is important for reducing the amount of air that leaks in and out, thereby cutting heating and cooling costs, improving durability, creating a healthier indoor environment and increasing comfort. However, if you seal your home too tightly, you could be putting yourself at risk from the dangers of backdrafting.
What is backdrafting
Backdrafting: Exhaust from a fan or natural gas-powered appliance is supposed to flow through a duct and out of the house. When exhaust doesn’t flow up and out, it backdrafts, spilling deadly carbon monoxide into the air inside your home.
It’s crucial that your home can breathe, with a proper amount of air entering and leaving. If you seal it too tightly, pollutants can get trapped in the home and affect your health. In addition, moisture can also build up and create mold or otherwise damage your home’s structure.
Backdrafting occurs when “the pressure differential that allows for release of combustion gases is overcome by low indoor air pressure, caused by a high rate of expulsion of air pushed outdoors, through exhaust fans, fireplaces and dryers,” says Nick Gromicko, founder of the International Association of Certified Home Inspectors. “Then, combustion gases can be sucked back into the house and may even cause death to the occupants.”
So, how can you be sure your home is sealed right but not too tight?
“The right thing to do is to get an energy audit before air sealing your home,” say the experts of Sellair, a company that underwent BPI Certification to properly conduct energy audits, as well as air seal and insulate homes.
Each home has a standard level of how many air changes it needs per hour. This is called the Building Airflow Standard (BAS), and it can be calculated after finding the volume of your home, which is based on its size and shape. Once this is determined, a blower door test will be needed to confirm how leaky or tight your home is.
A blower door test involves using a powerful fan that mounts into the frame of an exterior door. The fan works to pull air out of the house in order to lower the air pressure inside. The higher outside air pressure then makes its way in through the unsealed cracks and openings.
“You may seal up to 70 percent of the BAS levels before needing mechanical ventilation to bring more air into the home,” Sellair explains. “Then after air sealing is completed, run the blower door again to confirm your results. If you air seal too much, bring in mechanical ventilation to the home. This will give you adequate amounts of airflow and filter pollutants in the home.”
One of the biggest dangers of a home sealed too tightly is trapped carbon monoxide. The most common symptoms of carbon monoxide poisoning include: headaches, dizziness, drowsiness, nausea, vomiting, shortness of breath and tightness across the chest.
If sealing your home is on your home improvement to-do list, be sure to get an audit first!