Ventilation Systems Aren’t Just for “Tight” Homes

Happy couple breathing ventilated air

High performance homes typically need mechanical ventilation. Most people in the green building and home performance industries would agree with that statement.

After all, modern, energy efficient homes are very airtight compared to yesterday's construction. Without ventilation equipment, most experts reason, the air in those homes won't be healthy to breathe. It might even stink.

And no, opening the windows isn't always an option.

So it's smart to install ventilation systems in these homes. Energy recovery ventilators (ERVs) and ventilating dehumidifiers are good equipment options for our climate zone, and they can make an incredible impact on your ability to stay comfortable (and breathe easy) indoors. But here's the thing about mechanical ventilation equipment:

Everyone can benefit from it - not just people with "tight" houses.

Fresh, clean air is good for all homes (and all lungs)

Question: When is it good to breathe fresh, clean air?

Answer: Any time you're breathing.

It's simple, right? If you're breathing, which you are all the time, it's better to breathe clean air than it is to breathe dirty air. Nobody disputes this.

And yet we rarely breathe clean air when we're indoors. Why not?

For one thing, many people don't realize that indoor air is often dirty. Most modern homes contain lots of contaminants you don't want to breathe - things like:

  • Manufactured products that off-gas volatile organic compounds (VOCs)
  • Mattresses and carpets and curtains that off-gas and function as magnets for dust and pet dander.
  • Strong-smelling household chemicals and products with potent fragrances

The list goes on. And let's not forget about marginal air filtration and high summertime humidity, both of which contribute to high volumes of dust mites and even mold proliferation.

Indoor air can be pretty gross.

Even if you do realize indoor air is dirty, you might have heard that deliberate ventilation isn't necessary since your house "breathes" through gaps and cracks in the envelope. It's the argument made by home performance authorities who think mechanical ventilation is only necessary for tight houses. At PV, this is what we used to believe.

Then we changed our minds.

Air that naturally seeps into your home isn't always good to breathe.

First of all, we don't dispute that outdoor air probably leaks into your home and replaces the existing air without mechanical intervention. In most homes, this is true. What we dispute is the idea that infiltrating air is fresh. It isn't.

Unfiltered outdoor air isn't always healthy. It might contain…

  • Vehicle exhaust
  • Industrial pollutants
  • Organic allergens, like pollen

During the summer, outdoor air also contains humidity. In the winter, it's uncomfortably dry. Regardless of outdoor temperature, your home still "ventilates" with this air. But it might not be the sort of ventilation you want.

For these reasons, we think it's good for all homes to have some kind of mechanical ventilation system. That way, you can constantly replace dirty indoor air with filtered (and sometimes conditioned) outdoor air.

Put simply, you'll breathe a whole lot easier.

You're changing how the air infiltrates and making sure it's clean.

If you currently live in a "normal," non-high performance home, you may have a lot of air infiltration. By installing a mechanical ventilation system like an ERV or ventilating dehumidifier, you're not just "adding clean air to dirty air." You're actually changing the source of air infiltration to a cleaner source.

Here's a little building science for you. Your home allows a certain amount of air to enter and escape all the time. There are things that can affect the volume of air exchanged - windy weather, running kitchen fans, keeping doors open, etc. - but the equilibrium abides.

X amount of air leaks out. X amount of air infiltrates. Over and over again.

When you add, say… an ERV to your home, the same amount of air still escapes on a recurring basis. The same amount also infiltrates. That doesn't change. The rate of air exchange remains the same.

The difference is that the infiltrating air passes through the ERV (and an air filter) first. Instead of seeping in through little gaps between your crawlspace and your living room - and bringing mold and other yucky who-knows-what with it - the air is cleansed of all contaminants before it enters your lungs.

Depending on the mechanical ventilation method you choose, the air probably contains a more agreeable amount of humidity, too.

So you're not just mixing dirty and clean air! You're actually replacing the unhealthy air with healthy air the same way someone in a really tight home would do!

Ok, mechanical ventilation is great. What next?

In the Atlanta area, ventilating dehumidifiers (aka "fresh air" dehumidifiers) and ERVs are your primary choices. Both are fantastic options.

But if your main concern is indoor air quality, not dehumidification, we think an ERV is better. Why?

We'll be exploring that topic - ERVs (balanced ventilation) vs. whole-house dehumidifiers (positive pressure ventilation) - in our article next week!