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Does a House Need Ventilation?
Is the solution to pollution always dilution? For the most part, yes, but not always. So when does ventilation of your house make sense? How much? For how long? Don't all the leaks in my home take care of this? I regularly get asked questions like these by clients when I am in their homes trying to make them healthier. Let's look at the problem and break down the solutions to fit the situations.
The Problems With Home Ventilation Systems
We do many things inside our homes, like breathing, cooking, showering, and laundry. Sure, they are all everyday things. When we do any of them, we generate moisture, odors, and particles that can negatively impact our overall indoor air quality. How so?
Even when we breathe, we exhale carbon dioxide (CO2). Too much CO2 in a room, like your bedroom with the door closed at night, can elevate the CO2 levels enough to impact your sleep patterns.
When cooking, we create moisture from boiling water and baking food, as well as particulates from frying our vegetables on the stovetop. We shower, bathe, and do laundry that generates a great deal of moisture within our homes. In some cases, this moisture can accumulate and even spur mold growth in specific locations. To have the best possible air quality in our homes, we need to understand the sources that negatively impact our health and the strategies to minimize them.
Mechanical Ventilation
Why do I need mechanical ventilation when my house is leaky? Excellent question - we want balanced air. We don't want to bring in air from leaky wall cavities and crawlspaces. I also get the opposite question: with all this energy efficiency stuff, will my house become too tight? It is a big challenge to get all the air sealing done in an existing house to make it really tight. But, if you invest in air-sealing at home, you will save a lot of energy and increase your home's resilience.
Once you do this, you'll need to ensure that you have point source moisture and odor removal and a mechanical ventilation system for the house. The Passive House standard, probably the tightest home building standard out there, requires mechanical ventilation to ensure your house doesn't make you sick.
Let's discuss the three types of systems, to help you understand more about mechanical ventilation. These are exhaust only, supply only, and balanced whole-house systems.
Table of Contents
Exhaust Only Ventilation
Exhaust only ventilation is, by far, the most common option and works best in cold climates. In this case, a home utilizes existing fans - think bathroom and kitchen fans - to pull stale air out of the house. If your home is relatively leaky, this option may be all you need. If your home is tightly sealed, as mentioned above, you could be pulling air from attics crawl spaces and other areas where air quality is not ideal. Heating and cooling costs can be increased with exhaust only ventilation, as you are sending your conditioned air outside continually.
Supply Only Ventilation
In this scenario, a homeowner would install a fan to bring outdoor air into the house. In contrast to the above option, this allows you to choose where the air enters the house. This method of ventilation is usually best in warm climates. However, without adequate moisture control, it can lead to mold and mildew issues as well as increased heating and cooling costs.
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.
