Yes, but we need to control the breathing.
When buildings "breathe", they exchange interior air with exterior air through small cracks joints in construction. Air exchange between interior and exterior can be advantageous sometimes, but that air exchange needs to be designed specifically for the building.
Sick Building Syndrome, made famous in the unventilated tenement housing blocks in New York City, occurs when pathogens build up over time inside a building with less than optimal ventilation. Operable windows solved the problem long ago, but that solution came before interior air was conditioned year-round. Presently, in most of the US, interior air is cooled in the summer and heated in the winter.
In a typical house, small gaps in construction allow free exchange of air between the interior and exterior of the house. As anyone who places their hand next to an unsealed exterior door can tell you, exterior air infiltrates the building year round. You can bet that if you feel air pushing into your house in one location, a similar amount of air leaves your house in another location. Over time, and more quickly than you realize, all of the interior air in your house exchanges with air outside your house!
How much air are we talking about? Well, Joseph Lstiburek, my very favorite building scientist, puts it at around 5-7 air changes per house (ACH) in this paper. That means your HVAC system has to condition the air coming in from the exterior 5-7 times over every hour, every day, every year. Well, sort of — other things also affect temperature, like all the stuff in your house acting as a heat sink and preventing large temperature swings. But, to generalize the idea, think about losing all that nice conditioned air you paid for and replacing it with exterior air that needs to be conditioned to keep you comfortable.
In addition to the energy lost in the 5-7 ACH, pathogens can enter your home through gaps in construction. Dust is tiny. Pollen is tiny. Bugs are also tiny. If air infiltrates your home, other micro and not-so-micro things enter your home as well. Air also carries water molecules in the form of vapor (humidity), which can quickly change the comfort of the conditioned air in your house. Too much (or not enough) humidity will always be uncomfortable.
So, what can be done?
Install a monolithic air barrier on the house. A modern air barrier is often combined with other environmental control layers like a vapor barrier and a liquid water barrier. Products like this are called weather resistive barriers (WRB), but can also be called an air, vapor, and liquid control membrane depending on its properties. A good WRB placed correctly on the roof, walls, and tied into the crawlspace will prevent a considerable amount of air exchange. Additionally, to make sure the building turns over enough air to prevent Sick Building Syndrome, install a dedicated air intake manifold with HEPA filter. They cost around $500 and will keep your air as clean as a hospital operating room while reducing your energy bill!
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