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Unhealthy Ventilation: What You Need to Know
Haven't we already covered healthy ventilation? Yes, but we have not dived into the deeper issues of house ventilation gone wrong. Ventilation is of utmost importance because if ventilation and pressures are out of sync in a home, people can be at serious risk.
Table of Contents
The Analogy: Fish Tanks and Houses
Imagine your home is a fish tank. A beautiful, clean, lovely fish tank with happy fish and undersea castles and plants, all doing well. Fish tanks have aerators to add oxygen to the tank. What happens if the aerator turns off? The fish are not so happy, not so healthy. If it stays off for a long time, the fish will perish.
Most real-world ponds bring oxygen in through freshwater entering and exiting the water body. We have all seen and smelled stagnant ponds or the grime that grows on the fish tank if the water isn't changed regularly. Those are contaminants in the water.
Similarly, most of us have experienced a stuffy boardroom after an hour meeting when everyone is ready to nod off. This sleepiness occurs because of excess carbon dioxide, which we exhale, and not enough fresh oxygen entering the room.
Likewise, our homes require fresh air as well, for the same reasons. So we need air exchange in our homes to keep us healthy. This need for fresh air is genuine for very tightly sealed (not leaky or drafty) homes—a significant energy-efficiency tenet.
The challenge is how to deliver fresh air to our habitats. Sticking with the fish and water analogy: if you were to pour a whole bucket of water into your fish tank, it would spill over. If you were to bail out more water than you replace, the fish would be disappointed in your abilities to keep them alive. We need a balanced approach of the same amount of water coming in as going out. The more fish/people in the habitat, the more exchange of water/air required. Why? Because we breathe, sweat, and mess up the place more.
The Real Air Quality Problem: Back-Drafting
Let us assume that you have a relatively new or renovated home that is energy-efficient, in part because of a tightly sealed envelope. Now, let us picture the beautiful kitchen renovation you have saved up for, with a lovely gas stove and significant range hood overhead. The kitchen exhaust fan in the old kitchen was probably somewhere between 150 and 450 CFM (cubic feet per minute) exhausting outside. The new stainless hood and exhaust fan now may draw 800-1200 CFM of air out of your home when you turn it on. This powerful fan leads to a tremendous amount of air leaving your home in a short time.
Bottom Line on Healthy Home Ventilation
My recommendations: please consider installing an HRV or ERV if you do not already have one. If you do have one, or get one installed, make sure it is balanced. You can check this by looking for the balancing sticker on the unit's front, showing the high and low-pressure settings. If there is no sticker, do not pay the installer—that is my rule. Also, install some carbon monoxide detectors throughout the house, especially near your gas appliances. Better yet, replace your gas-powered appliances with all-electric, so there is no carbon monoxide in your home. By following these steps, you can breathe a sigh of relief, knowing you have safe and fresh air.
Stephen Collette
Stephen Collette is a Building Biologist, Building Science Consultant, LEED Accredited Professional, and a Heritage Professional. Stephen is the owner of Your Healthy House and lives in Lakefield, ON with his wife and 2 daughters.
