Indoor Air Quality vs. Energy: A False Choice –Take the Long View with Integrated Solutions
Alan Scott, FAIA, LEED Fellow, WELL AP, CEM – Intertek Building Science Solutions
David Okada, P.E. – Engineering Economics, Inc.
Brendon Mattis, P.E. LEED AP – Engineering Economics, Inc.
(Part 1 of 2)
Three building science professionals collaborated to author this industry paper. In this two-part series, they recap the latest understanding of human health and performance impacts of indoor air quality, describe what’s behind the growing imperative for energy-efficient, low-carbon buildings, review the evolving standards and policies, and outline an approach to integrated solutions to optimize multiple building performance parameters.
It is not surprising that the COVID-19 pandemic significantly increased public awareness of indoor air quality (IAQ) and the role of buildings in supporting occupant health. The pandemic also accelerated a previous trend toward built environments that promote health and wellness.
Now more than ever, we are aware of how effective ventilation, improved filtration, and elimination of pollutant sources serve to reduce pathogen transmission risk, improve cognitive performance, and enhance overall health and wellness.
At the same time, the reactive approach to reducing pandemic risks in buildings has often included increasing outside air ventilation, consequently increasing energy use, highlighting a historic conflict between two potentially competing goals: improving IAQ and reducing energy use.
This is in many cases a false choice, as integrated solutions are available to optimize both the health of occupants and the energy performance of buildings.
What is at Stake with IAQ?
Carbon Dioxide and Cognitive Health
Contrasts between our pre-, during, and emerging post-pandemic lives align with research that points to dramatic benefits from improved air quality. The Atlantic and Science report that widespread adoption of higher ventilation rates has the potential to largely eliminate future airborne disease transmission (Coronavirus Ventilation: A New Way to Think About Air – The Atlantic). Meanwhile, evidence is suggesting that carbon dioxide (CO2) itself may negatively affect our health and cognition at common indoor levels (Stumm, R 2022, ‘Revisiting the 1,000 ppm CO2 Limit’, ASHRAE Journal. June 2022, pp. 14-22).
The Harvard T.H. Chan School of Public Health’s third Cognitive Function study, a global, longitudinal study, quantifies the effects of IAQ on the speed and precision of cognitive function in office workers (>300 participants in 6 countries). This study found that participants’ response times and proficiency on cognitive tests declined with increasing concentrations of particulate matter (PM2.5 ≥ 12 µg/m3) CO2, with measurable difference observed between concentrations as low as 400 to 800ppm of CO2. Previous studies by Harvard and others have shown similar correlations between concentrations of CO2 and other pollutants and cognitive performance, including finding measurable declines in student math and reading test scores in classrooms with CO2 levels above 900ppm.
These results ring true to anyone who has struggled to stay alert during a crowded meeting or lecture, but they also point to the fact that this is a problem we can solve, and not an inevitability.
IAQ and Work Productivity
Indoor air quality is central to a broader approach to indoor environmental quality (IEQ), which includes thermal, visual, and acoustic comfort. Combined, numerous studies show that improved IEQ results in increased productivity, reduced absenteeism, better sleep quality, and general wellbeing, thus providing economic benefits to employers.
The financial benefits of improved IEQ have shown to be substantial. In an office environment, the typical productivity increase from enhanced IAQ is expected to be worth $6,500 per employee per year in salary, with total employer benefit of about $8,800 per employee per year including benefits and reduced absenteeism.
According to the CDC, absenteeism alone costs US employers $225.8 billion per year or $1,685 per employee. In terms of priorities, salaries and benefits represent ~86% of business operating costs, compared to 8.9% for space lease and 0.8% for energy.
One study by the American College of Occupational and Environmental Medicine (Grossmeier, et al 2015) compared the increased value of 45 companies with high health and wellness assessment scores to the S&P 500 over a six-year period. The average company in the study appreciated by 159%, but the companies with robust health and well-being performance had a 235% augmentation in value.
Climate Change and Carbon Emission Reduction
Concurrent with the growing awareness of IAQ, the urgency to address the global climate crisis is increasing. Ironically, it is climate change and increasing CO2 emissions that result in the increased outdoor and indoor concentrations of CO2 that are contributing to poor IAQ. In addition to rising global background level, cities are now experiencing “CO2 domes,” with outdoor concentrations of 500ppm or higher, leading to calls for an absolute rather than relative standard for indoor CO2. As outdoor CO2 levels increase, more ventilation is required to maintain the same indoor concentration. Changing temperature and humidity also affect the behavior of various sources of air contaminants, including plants (pollen), fungi, and bacteria.
Making matters worse, much of the western United States is experiencing multi-year droughts exacerbated by climate change that are resulting in catastrophic wildfires. These in turn generate high levels of particulate matter and other pollutants, creating hazardous air quality both outdoors and in buildings. It is no surprise that many building engineers feel trapped in an unwinnable situation.
Clearly, we cannot focus on one of these issues and ignore the other. The good news is, we don’t have to choose, as in reality, there is no ventilation-energy trap. We can and must address these issues together, and emerging technologies are giving building owners and designers more options to accomplish this.
Policy and Regulatory Action
The United Nations Intergovernmental Panel on Climate Change Sixth Assessment Report released in April 2022 includes dire warnings, with a glimmer of hope that if global greenhouse gas (GHG) emissions are halved by 2030, we may still be able to avoid the worst consequences of global climate change. The COP 26 climate summit in Glasgow, Scotland, in 2021, highlighted the importance of building energy efficiency and carbon emission reduction to meet global targets. The main message is that we must take bold action now to avert severe human, environmental, and economic consequences.
In the United States, bold building sector action is taking the form of:
- American Institute of Architect’s Architecture 2030 commitment, making energy performance and carbon emission reduction a professional imperative for new building design and existing building renovations,
- Rapid proliferation of Building Performance Standards that set hard limits, with significant penalties, for existing building energy consumption and associated emissions, and
- The push for building electrification in multiple jurisdictions, including bans on new natural gas hook-ups in many cities, concurrent with the growth of renewable energy generation (grid decarbonization), to reduce greenhouse gas emissions associated with fossil fuel use in buildings.
These changing regulations are affecting both the design of new buildings and driving upgrades in existing buildings that have largely been ignored, and they can be addressed without sacrificing IAQ.
Evolving Indoor Air Quality Standards
In North America, ASHRAE Standard 62.1 Ventilation for Acceptable Air Quality is the main reference for designing, constructing, and operating buildings where IAQ is concerned. This standard is the basis for mechanical code ventilation requirements throughout North America, and for most in the HVAC business, its tables have held the answer for the “right” amount of ventilation for commercial and public buildings.
However, looking through the lens of the COVID-19 pandemic and recent research, it is important to remember that ASHRAE Standard 62.1 is a model regulation setting a minimum threshold below which ventilation rates are unacceptable. It should not be taken as an optimal or healthy level of ventilation.
Reviewing the history and limitations of ASHRAE 62.1 helps to understand how the current standard fits into IAQ considerations in project design and building operation:
- Recent versions of ASHRAE 62.1 define acceptable indoor air quality as “air in which there are no known contaminants at harmful concentrations, as determined by cognizant authorities, and with which a substantial majority (80% or more) of the people exposed do not express dissatisfaction.” Note that the focus is on the perception of air quality by occupants, not an objective measure of health outcomes.
- By contrast, other standards (including the original version of ASHRAE 62.1) have provided recommended airflow ranges for good IAQ. For example, the European (CEN) standards 13779 and 16779 (the analog of ASHRAE 62.1 in the European Union) offers both a minimum requirement as well as recommended ranges. ASHRAE moved away from this and does not provide info on a range for good IAQ.
- ASHRAE 62.1 has significant limitations in its definition of acceptable indoor air quality.
- It should ideally be based on scientifically measured objective outcomes for health and productivity, but instead uses subjective measures and rough estimates intended to avoid only the worst health outcomes (e.g. acute sick building syndrome).
- Ventilation rates should be tailored to mitigate disease transmission risk, as well as chronic/long term health risks for a diverse population, but the current standard does not address these.
- Having 20% of occupants dissatisfied is an inappropriately low threshold for acceptability.
- Where there is ambiguity in the current science, the standard should take the precautionary principle and err on the side of protecting occupant health rather than the status quo.
- Through the early 2000s, ASHRAE 62.1 ventilation rates were intended to balance concerns for IAQ and energy use, however other standards and codes have resolved this issue by requiring energy recovery, making this balance outdated. An appropriate current balance would use much higher airflows for significantly improved air quality.
- ASHRAE 62.1 is generally slow to be updated, so with human health and performance in the balance, we don’t want to wait for it to catch up.
Other organizations have stepped in to provide guidance. Several voluntary standards and rating systems, including the WELL Building Standard (WELL), US Green Building Council Leadership in Energy and Environmental Design (LEED), and RESET, have established performance-based standards, guidelines, and recommendations for IAQ derived from recent academic studies. These criteria typically include indoor contaminant thresholds as well as ventilation rates.
For example, WELL sets a PM2.5 threshold of 15 µg/m3 (based on World Health Organization guidelines) and recommends a maximum indoor CO2 concentration of 900ppm (about 500ppm above ambient outdoor levels) for enhanced ventilation design.
While the LEED rating system has long promoted exceeding ASHRAE Standard 62.1 by 30%, many studies looking at health, cognition, and productivity align on a sweet spot for cognitive benefits and lower airborne disease transmission in the range of 30 to 40 CFM per person – about twice the ASHRAE ventilation rate.
ASHRAE and the public health community are calling for more research on higher ventilation rates and health. This research will no doubt inform future standards, guidelines, and codes, but these processes will take years to produce documents and guidance for implementation. Building owners now need qualitative criteria to target their current operations, capital improvement plans, and designs.
Existing Building Challenges
Many existing buildings are not meeting current minimum standards. The root issue is undervaluing IAQ's impact on occupants and avoiding responsibility for it. This standard of practice is shifting from “assuming it is good enough” to “ensuring it is working right.” In addition to taking responsibility, building operators require complete information and, in many cases, strategic system upgrades.
There are numerous studies demonstrating underventilation and poor air quality in schools, offices, and other buildings, which suggests that there is significant room for improvement. To cite one example, a study in Texas found that CO2 concentrations exceeded acceptable thresholds in 66% of tested classrooms.
Based on our experience, anyone involved in checking or adjusting ventilation during the pandemic can attest to the many common reasons that systems underperform:
- Little to no record of ventilation rates in original design documents or tenant improvement records.
- Many buildings were designed without full consideration for delivering outside air to occupants. Before 2004 (when ASHRAE 62.1 addressed outside airflow to all spaces, including the most ventilation-constrained critical zone), the standard design practice was to only ensure enough outside air was getting into the building as a whole. Many of these buildings have inadequate heating capacity to deliver enough outside air to interior spaces in the winter without over-cooling them.
- Air handling units were typically not equipped to directly measure and control outside airflow, instead, they were set to provide the “design” ventilation rate at specific design supply airflow. As system flows change in response to real-time heating and cooling needs, the actual outside airflow also varies with no correlation to ventilation needs.
- Building controls typically did not include measurement hardware that operators would need to track or verify outside airflow. Without these measurement components, manual airflow measurement is a challenging process requiring specialized skills and equipment.
- Operational practices focus on responding to complaints. Short of sick building systems, low ventilation rates are not easily perceived compared to temperature, lighting, and housekeeping issues, generating fewer complaints. Many building operators do not view ensuring ventilation and IAQ as their responsibility.
- HVAC maintenance checks generally focus on ensuring components work individually, but don’t verify they all work together properly in “minimum outdoor air” mode.
- Deferred maintenance may mean some components are simply not functioning.
- Antiquated control equipment can prevent monitoring or adjusting systems.
- System overrides left in place keep the system from functioning properly.
- There is no legal requirement to keep existing buildings up to current standards.
Given this context of history and standards, and evolving demands for healthier indoor environments and decarbonization of buildings, we clearly need new, integrated approaches to the design of new and renovated buildings and the operation of existing buildings to meet new expectations. In the second part of this series, we will explore the role of commissioning and integrated thinking to meet these new challenges and expectations and review the key strategies for improving both IAQ and energy performance.
End of Part 1.
Readers: The September 9 Checklist will present Part 2 of this two-part paper, reviewing how the integrated commissioning approach guides solutions to achieve multiple goals, and diving deeper into specific solutions to improve both energy efficiency and IAQ.