HVAC - It’s All in the Air

By Jason Hudspeth, Senior Architectural Designer, Certified Passive House Consultant

In our introductory post, we discussed a frequently cited EPA report on air quality from 1989 which stated that Americans spend 90% of their time indoors. Well what if I told you there is another alarming statistic from the United States EPA, and that it is also from the 80’s!? Truly outrageous. This one, from the T.E.A.M. study, also examined indoor air quality and found that “concentrations of some pollutants are often 2 to 5 times higher than typical outdoor concentrations,” and this was in 1987.

And what is in this air? In addition to what you might bring in by choice or accident, it includes an airborne soup of other delights, including – but not limited to – the following: VOC’s (volatile organic compounds, including formaldehyde), bacteria, molds, pollen, dust mites, cleaning solutions/products, smoke/combusted elements, carbon monoxide, natural gas, radon, ozone, pesticides, asbestos, lead, arsenic, and VIRUSES. According to the CDC, “Some biologic pollutants, such as measles, chickenpox, and influenza are transmitted through the air. However, the first two are now preventable with vaccines. Influenza virus transmission, although vaccines have been developed, still remains of concern in crowded indoor conditions and can be affected by ventilation levels in the home.”

This information from the CDC comes to us from 2006, well prior to the current pandemic. What we do know at this time is that COVID-19, like Influenza, can be transmitted through the air, and that crowded indoor conditions can facilitate a high level of exposure and transmission. Between our near-exclusive relationship with our places of domicile and these stats, we’re convinced one should ever stop wearing their face mask.

As designers, we start by asking what solutions we can provide to combat this dystopian medley of pollutants, contaminants, and viruses.  Increased ventilation, when provided by a dedicated mechanical system, improves indoor air quality by bringing in fresh outdoor air while simultaneously exhausting the unhealthy indoor air. Coupled with appropriate levels of filtration, these controlled ventilation systems are a feature that can be used to dramatically improve the healthfulness of the interior air supply.

High Performance Buildings + Mechanical Ventilation Systems

When designing high performance buildings, we turn to mechanical ventilation systems for several reasons. First off, a high-performance building is unconventional (for now) in a number of ways. It is extremely airtight, and this limits the infiltration of air that is common in conventional construction assemblies.

This section diagram illustrates the ERV system used in the Empowerhouse, for which Jason Hudspeth was Team Project Architect. The system works by bringing in fresh outdoor air while simultaneously exhausting the stale interior air. Energy is transferred during the process to either cool or heat the incoming fresh air.

Air tightness is great until you cram a room with 20 breathing bodies and a dog, and you start to generate lots of heat and vapor.  Uncontrolled humidity within stagnant air quickly becomes unbearable; your walls are sweating, your people are sweating, and we need active ventilation to prevent things like mold from joining your party.  As high-performance building designers, we know to anticipate this – and plan accordingly.  The dedicated mechanical ventilation system manages this to provide the required air changes per hour according to performance criteria that are determined by climatic conditions.  It is coupled with a high-efficiency recovery system that transfers heat from the warm exhausted air to the cold incoming fresh air (winter scenario, which can reverse in summer), thereby further improving the energy efficiency of the building.   These systems also incorporate filtration systems, which remove many harmful contaminants from indoor air.

You want all of these features to be a part of your next project, and you want your next project to be a high-performance building with mechanical ventilation.  You just didn’t know why – until now.  We will help guide you through the process that will ensure your next building is also good for your health and well-being.  If you are interested in learning more about the benefits of this approach, please reach out to us with your questions, or check out some of the resources available via our member affiliation with the New York Passive House network.