The building you’re in right now may be affecting how clearly you think.
In 2016, researchers at Harvard T.H. Chan School of Public Health conducted a landmark study that changed how scientists and building professionals think about indoor environments. The COGfx study — led by Dr. Joseph Allen and colleagues — looked at whether the quality of air in a building affects cognitive performance.
The results were striking.
What Harvard’s COGfx Study Found
In a double-blind, repeated-measures crossover design, 24 professional workers spent time in three different building conditions:
The results showed that “cognitive scores were 61% higher on the Green building day and 101% higher on the two Green+ building days than on the Conventional building day (p < 0.0001)" (Allen et al., 2016, *Environmental Health Perspectives*, PMC4892924).
To be clear about the study’s design: this was a controlled setting, n=24 workers, with multiple building conditions varied simultaneously. The researchers themselves note that ventilation, CO₂ levels, and VOC exposure were changed together rather than in isolation. The 101% figure represents a composite effect across multiple improvements.
Still, the directional finding is consistent with a growing body of research: the air quality in the spaces where we work and live is associated with how well our brains function.
What This Means for Your Home Office
Since 2020, millions of Canadians have shifted to working from home — at least part of the time. For many high-achieving professionals, the home has become the most important workspace.
And yet, home offices are rarely designed with air quality in mind.
Most home offices are in spare bedrooms or converted spaces with limited ventilation. They may have off-gassing furniture, inadequate air circulation, and rising CO₂ levels during long work sessions. None of this shows up as an obvious problem — but it may be affecting performance in ways that are real and measurable.
The Harvard Healthy Buildings Framework
Dr. Allen and his colleague John Macomber at Harvard Business School have since expanded this research into a comprehensive framework called the 9 Foundations of a Healthy Building. The nine foundations are:
1. Ventilation
2. Air Quality
3. Thermal Health
4. Moisture
5. Dust & Pests
6. Safety & Security
7. Water Quality
8. Noise
9. Lighting & Views
The framework is evidence-based and designed to be practical. Allen and Macomber’s book, *Healthy Buildings: How Indoor Spaces Drive Performance and Productivity* (Harvard University Press, 2020), presents the business case for investing in healthier indoor environments.
The key argument: healthy buildings are more productive buildings. Every dollar invested in improving indoor air quality has a measurable return.
Applying the Research at Home
You don’t need to retrofit an entire building to benefit from these principles. Here’s how to apply them in a residential context:
Ventilation: Make sure your HVAC system is circulating air effectively, not just recirculating the same indoor air. An HRV or ERV brings in fresh outdoor air while recovering heat — the best of both worlds.
Air Quality: A high-quality furnace filter (MERV-11+) traps fine particles before they circulate through your home. For rooms with limited ventilation, a standalone HEPA air purifier is an effective addition.
Thermal Health: Comfortable, consistent temperatures aren’t just about comfort — they affect focus and sleep quality. A well-maintained heating and cooling system that maintains steady temperatures room-to-room makes a real difference.
Moisture: 40–50% humidity is the evidence-based target. Too dry, and your airways and skin suffer. Too humid, and mold and dust mites become a problem.
A Note on the Research
It’s worth being precise about what this research shows and doesn’t show. The COGfx study is a controlled experiment with a relatively small sample. The 101% improvement reflects a multi-variable improvement in building conditions, not a single change. And cognitive function tests in a laboratory setting don’t directly translate to every aspect of real-world performance.
What the research does establish, with statistical significance, is that the air quality in a building is associated with measurable cognitive outcomes. That’s the starting point for a serious conversation about how we design the spaces we live and work in.
Next: Harvard’s 2024 Gut Microbiome Study: What Cleaner Indoor Air Did to Participants →
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Sources: Allen, J.G. et al. (2016). Associations of Cognitive Function Scores with Carbon Dioxide, Ventilation, and Volatile Organic Compound Exposures in Office Workers. Environmental Health Perspectives. PMC4892924. | Allen, J.G. & Macomber, J.D. (2020). Healthy Buildings. Harvard University Press.
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