Breathing fresh air indoors by design

Maybe you are like me - you can’t even count the number of times the building’s air-conditioning made you uncomfortable - to the point of distraction. I hope you also remember being in a building that provided noticeable comfort – and no distractions.

During a visit to a factory in Denmark many years ago, I experienced a conference room ventilated with 100% outdoor air. The meeting room was at capacity, but it never reached the point of feeling stuffy. Nearly 25 years later, I still remember the sense of being outdoors. It was more like sitting on a bench outdoors than sitting in a conference room full of colleagues. This is my first memory of being in a building designed with its occupants in mind.

Today, designing buildings for occupant well-being receives unprecedented levels of attention. Even before COVID-19 raised awareness of the importance of proper operation of a building’s HVAC system, the WELL Standard was promoting and standardizing how buildings are designed, built, and operated with occupant health as a primary objective. So, when I had the opportunity to study for the WELL AP exam, I was particularly interested to learn about the requirements of the WELL v2 standard with regard to HVAC system design.

Air is the first WELL Concept discussed in the current version (WELL v2). Within the Air Concept the Enhanced Ventilation optimization offers three credits toward certification for the “implementation of advanced ventilation strategies that can achieve higher air quality levels and thus benefit human health and productivity.” Building designers can meet the requirement by choosing between 1) increased air supply or 2) demand control ventilation (DCV).

Any time we increase the flow of air beyond that required by code, we risk causing the outdoor air fans to work harder and consume more energy. We compound the problem by increasing the flow of air to rooms that are not at full occupancy. WELL v2 cites scientific research indicating that increased airflow doesn't necessarily increase energy use - it depends on how the system is controlled. DCV and other control strategies figure prominently. Quoting from WELL v2: “A demand-controlled ventilation (DCV) system regulates the outdoor air ventilation rate to keep CO2 levels less than the thresholds specified”. Properly designed DCV systems can deliver extra ventilation for wellness and comfort while saving energy.

WELL V2 is not the only building certification program promoting the indoor environmental quality benefits of DCV. The Passive House concept described by Passive House Institute (PHI) includes a requirement for variable flow to assure occupant comfort and increased energy efficiency. Case studies and seminar presentations have been made about the benefits of DCV in Passive House applications in North America. Then why do so many Passive House projects still use a constant Air Volume control strategy? DCV technology isn’t new, so there should be no fear of life on the bleeding edge. The lifecycle cost savings has been proven, so owners should prefer DCV.

DCV has been around long enough that there is ample evidence that the concept works. Recent evidence is contained in the ASHRAE Journal, Vol. 65, no. 5, May 2023 article titled Air Quality-Based Ventilation for Hospital Energy Conservation, where the authors discuss the energy savings experienced by converting a hospital ventilation from constant-volume to variable volume, then from variable volume to an air-quality based DCV System. The article is summarized by one of the authors in the May 2023 episode of ASHRAE's Hot Air podcast. Visit the ASHRAE Technology Portal to read the full article.

We’ve come a long way

“Those who cannot remember the past are condemned to repeat it.” - George Santayana

I’ve heard it said that the greenest building is the building that is already built. While that may be largely true, not all existing buildings were constructed with recent knowledge of what makes a building healthy for occupants. I’ve seen another beautiful thermostat in an old building. This thermostat has concealed fastening and is thus a bit nicer to look at than the thermostat shown in the last edition. Both have that nice silvery column of Mercury. I remember playing with Mercury from a broken thermometer once. Today, the health hazards of Mercury are well known– it is bioaccumulative, and exposure to Mercury can result in a list of serious effects in humans and we wouldn't knowingly install a Mercury thermostat in a new building today. The WELL standard not only provides guidance on designing ventilation systems for occupant well-being but also on designing the entire building to be free of unsafe materials like Mercury. As for me, given the opportunity, I would not with Mercury in the event of a spill!