Healthy Buildings, written by John Macomber and Joseph Allen is, as the title suggests, a book about how buildings affect health. Allen is a former environmental consultant, professor of public health, and director of Harvard’s “Healthy Buildings” program. Macomber is a lecturer in finance (also at Harvard), and formerly worked in both real estate and construction.
Healthy Buildings originally came out in April of 2020 - fortunate, in the sense that the spread of COVID-19 generated a great deal of interest in how buildings impacted health (particularly air quality), but unfortunate in that the book originally had relatively little to say about the spread of airborne pathogens indoors. An updated version that came out in 2022 adds a chapter on how buildings can prevent airborne pathogens from spreading.
The basic argument of Healthy Buildings is simple. Modern society has created a large number of rules to protect the environment, both because we think the environment is valuable in itself, but also because we realize that a dirty, polluted environment can negatively impact people’s health. Clean air regulations such as the Clean Air Act, for instance, were created largely as public health measures.
Environmental regulations such as the Clean Air Act, the Clean Water Act and the Ocean Dumping Act typically regulate and set environmental standards for the outdoor environment - what goes on outside of buildings. The National Ambient Air Quality Standards (NAAQs), for instance, limit pollutant levels in atmospheric air, but say nothing about the air quality within buildings.
But people spend nearly all their time indoors. Americans spend 90% or more of their time indoors, “more time than some whales spend underwater”. Despite this, comparatively little attention has been paid to the quality of our indoor environment, and how it might be affecting our health. Allen and Macomber argue that indoor environments are often unhealthy (or less health encouraging than they could be), and that this inflicts huge costs in terms of health outcomes and lowered productivity. But just as major gains in public health were achieved with outdoor environmental regulations, indoor environmental regulations, in the form of new or updated building standards and requirements, could greatly improve public health.
Negative indoor environmental effects
Allen and Macomber go through a variety of ways that indoor spaces can negatively impact health.
The largest, most important one is ventilation and air quality. Current ventilation standards (such as ASHRAE 62.1 and 62.2), consider occupant health (along with comfort), and are designed to minimize pollutant concentrations, but they (according to Allen and Macomber) don’t go far enough. They also don’t include considerations for things like minimizing airborne pathogens. And standards such as 62.1 and 62.2 are design standards - they stipulate what ventilation performance should be achieved at the time of construction, but there’s little in the way to ensure that this is achieved during actual operation. In practice, buildings often have ventilation rates and measures of air quality that are substantially below design requirements.
CO2 concentration, for instance, should be below 1000 parts per million (ppm) in a building meeting ASHRAE ventilation standards, but studies suggest that buildings often have much higher CO2 concentrations. Allen and Macomber note a study of 28 schools that found average CO2 concentrations were 1500 ppm, and in another study of schools in Texas, one in five had CO2 concentrations above 3000 ppm. Measurements of office buildings likewise routinely find that ventilation rates are below recommended ventilation rates. And a report produced for the UK’s Royal Academy of Engineering (based on interviews with experts) estimated that 50% of public buildings in the UK had an ineffective or inadequate ventilation system. These low ventilation rates are exacerbated by the fact that commercial buildings often turn off their HVAC systems in the evening, even if people are still in the building.
Low ventilation rates can have a variety of negative effects. One major one is increased CO2 levels. While elevated CO2 doesn’t have health impacts until it reaches very high levels (~6000 ppm), reduced cognitive performance seems to occur at much lower levels. A study done by Allen of office workers that compared “typical” indoor CO2 levels (~1000 ppm) to lower and higher levels (500 and 1500 ppm) found that cognitive performance declined as CO2 levels rose. Other studies have found similar results. Allen and Macomber estimate that increasing ventilation to double the ASHRAE recommended value could increase cognitive performance by anywhere from 2 to 10%.
More generally, high levels of indoor pollutants caused by inadequate ventilation cause something known as “Sick Building Syndrome”, where long periods spent indoors cause a variety of symptoms such as “headache, eye, nose, and throat irritation, fatigue, dizziness, and nausea”. Sick Building Syndrome began to appear in the 1970s, as buildings were built increasingly airtight due to energy efficiency concerns without making commensurate changes to their ventilation systems.
Poor ventilation is also responsible for increased spread of airborne pathogens. As the Aerobiological Engineering Handbook notes, airborne pathogens are overwhelmingly likely to spread indoors:
Most microbes die off in the outdoor air as a result of sunlight, temperature extremes, dehydration, oxygen, and pollution.- outdoors, viruses and other infectious agents quickly get diluted in the atmosphere, destroyed by UV light, or by heat or cold…Controlled indoor climates favor the survival and transmission of contagious human pathogens as well as some outdoor fungi and bacteria. Since people spend over 90 percent of their time indoors, the solution to the problem of most airborne infections, therefore, lies in engineering control of the aerobiology of the indoor environment.
Whenever we breathe, talk, cough, or sneeze, we’re emitting small particles (called “aerosols”) into the environment. When we’re sick, pathogens will hitch a ride on these particles, and can infect anyone that inhales them. Prior to COVID it was thought that most pathogens spread via large diameter aerosol “droplets” which fell out of the air quickly, but more recent studies seem to show that smaller “droplet nuclei” are an important vector of infection. These smaller aerosols can stay aloft for 30 minutes, in some cases even hours. The more pathogen-containing particles accumulate in the air, the greater the chance of occupant infection. Most COVID outbreaks occurred in situations where people were spending large amounts of time in poorly ventilated spaces.
By increasing ventilation, either directly (by replacing indoor air with outdoor air that doesn’t have infectious aerosols) or by increasing “effective” ventilation using filtration or disinfection technologies (such as HEPA filters or UV lights), infectious aerosols can be removed or deactivated, reducing the likelihood of infection. The previously mentioned UK report estimated that indoor airborne infections (including COVID, but also things like influenza) could be reduced by 30-50% in the worst performing buildings by bringing ventilation rates up to the equivalent of ASHRAE standards. And future technologies might be able to reduce this even further. UV light, for instance, can destroy or inactive pathogens, but exposure is also harmful to humans. Current UV light disinfection systems are thus either placed in ducts or just treat the air near the ceiling (called upper room UV), limiting how much air they can treat at once. But a new UV technology known as Far UVC uses a wavelength that appears to be safe for human exposure, and could potentially treat very large volumes of air at once. Indoor airborne infections (both pandemics and seasonal infections) cost on the order of 1% of GDP every year in medical costs, deaths, and lost productivity, so even a slight reduction in the frequency of airborne infections could save billions of dollars annually.
And air quality isn’t the only way that buildings can cause infection and disease. Allen and Macomber make repeated reference to Legionella, a bacteria that thrives in lukewarm, stagnant water and can cause the deadly Legionnaire’s Disease. Legionella can grow in air conditioners, cooling towers, or in “dead legs” of plumbing (where a plumbing fixture gets removed but the pipe serving it is left in place). It’s estimated that there are on the order of 10,000 to 20,000 cases of Legionnaire’s Disease in the US each year. ASHRAE has recently created a standard (ASHRAE 188) to reduce the risk of Legionella, but adoption of it has so far been relatively limited.
Other than poor ventilation, the other major health risk that Allen and Macomber note is the presence of chemicals. Almost all building products - carpet, flooring, wallboard, ceiling tiles, insulation, grout, etc. - are made using a variety of industrial chemicals, which make their way into our bodies over time. Over 200 industrial chemicals can be detected in the blood of Americans and residents of other industrial countries. These chemicals are often endocrine disruptors which interfere with the function of hormones - Allen and Macomber note a study that analyzed the dust of 46 buildings, and in every single case the dust was found to be hormonally active. Other chemicals interfere with immune system function, or increase the risk of cancer. These are often so-called “Forever Chemicals”, which have carbon-fluorine bonds which give them useful properties as sealants and stain repellents, but which mean they never fully break down in the environment. Building products also often emit volatile organic compounds (VOCs) such as formaldehyde.
Regulation of these chemicals is a challenge. Allen and Macomber note that there are over 80,000 industrial chemicals in use, with 2000 more being added every year, but only 300 of these have been evaluated for health and safety. When a chemical does get banned, its frequently simply replaced with a similar chemical with similar toxicity. Bisphenol A (BPA), for instance, began to be phased out after studies showed that it was toxic, but it was largely replaced by bisphenol S (BPS), which has both similar functionality and toxicity. BPS, in turn, is now being replaced with another similar chemical, bisphenol F (BPF). A forever chemical known as C8 was replaced with similar chemicals C6 and C10 as the toxicity of C8 became known. And building products advertised as “formaldehyde-free” have often simply replaced the formaldehyde with other, similar aldehydes. Because there’s no equivalent of “nutrition facts” for building products, it’s often difficult to know whether a building product has any concerning chemicals in it - suppliers themselves will often not know.
In addition to chemicals and ventilation, Allen and Macomber briefly discuss a variety of other ways that buildings can be designed to improve health, such as keeping temperature in the optimal range, minimizing noise, and having lighting that matches the temperature of daylight, but air quality and indoor pollutants are the major focus of the book.
So what are we to do?
Allen and Macomber have two broad strategies for turning these health recommendations into actual changes in the built environment.
The first is to show that interventions to make buildings healthier can have positive economic returns. Better air quality in an office means employees that are sick less often and have higher cognitive performance. Because the cost of employees is much higher than the cost of the building itself (Allen and Macomber suggest a ratio of 3-30-300 as the relative costs of utilities, rent, and payroll for a typical business), a relatively small increase in productivity is worth a large increase in building costs. Allen and Macomber go through a variety of pro formas to show that changing a building to be healthier (such as by increasing ventilation rates to double the ASHRAE minimums) can be a win both for the building owner (in the form of higher rents that more than offset the additional HVAC costs) and the tenant (in the form of greater productivity that more than offsets the additional rent and utility costs).
But this economic argument on its own is unlikely to be enough. For one, most buildings aren’t office buildings where there’s an obvious return on investment from a healthier space. For another, there are often what Allen and Macomber call “split incentive” problems, where the costs and benefits accrue to two different parties. In one case, for instance, a hospital that had just spent millions of dollars settling a Legionella lawsuit was unwilling to spend $20,000 to upgrade its facilities to prevent future Legionella cases - the lawsuit had been paid for by the insurance company, whereas the $20,000 would have come out of the facilities budget.
To combat this, Allen and Macomber recommend following in the path of green building standards, particularly LEED. LEED is a green building standard first created in the 1990s, which gives certifications to buildings that achieve certain levels of “green construction.” Buildings are awarded credits for things such as reusing on-site rainwater, having electric vehicle charging stations, or having energy performance above code requirements. The more credits you get, the higher level of certification awarded, with the highest being “LEED Platinum”.
LEED has become very popular, with on the order of 300 million square feet of LEED certified space added annually in the US. In Allen and Macomber’s view, LEED achieved this by making the “green” aspects of the building more legible - while things like low VOC building materials aren’t necessarily noticeable by tenants, a big plaque in the lobby broadcasting LEED certification is noticeable. By making green construction legible, LEED unlocked demand for more environmentally friendly buildings that was already there, and the market responded by providing more of them. Allen and Macomber suggest a similar development is possible for “Healthy Buildings”, and go through a variety of currently existing Healthy Building certifications that might help achieve this, most notably the WELL standard.
Unfortunately, I think Allen and Macomber are overestimating the amount of work we can expect voluntary standards to do for healthy buildings. They suggest LEED as an example to follow, but to me LEED is much more illustrative of the limits of voluntary standards.
For one, the majority of buildings in the US are not LEED certified. There are roughly 300 million new square feet of LEED certified buildings in the US each year, but the US builds roughly 1.6 billion square feet of commercial buildings each year, along with around 2.2 billion square feet of single family homes and 400 million square feet of multifamily apartments. In other words, less than 10% of new building square footage is LEED certified, less than 20% if we only consider commercial buildings (most LEED buildings are likely commercial buildings).
For another, the benefits of LEED are not as strong as Allen and Macomber suggest. For instance, one of the major supposed benefits of LEED is improved energy efficiency, and Allen and Macomber cite a study suggesting that LEED buildings use 20-40% less energy per square foot than comparable non-certified buildings. But this study is simply a model that uses data on what the buildings were designed to save. Actual measurements of LEED and non-LEED buildings show that lower levels of certification don’t use any less energy than non-LEED buildings, and it’s only at the higher levels (Gold and Platinum) where energy savings is observed. Likewise, LEED offers many credits for indoor air quality, but a study of air quality in schools found that LEED certified ones did not have any better air quality than non-LEED schools (in fact, a LEED school had by far the worst air quality of any school tested).
When higher levels of LEED certification are adopted, it’s often because jurisdictions either require them, or because they offer the developer incentives to do so. The City of Seattle, for instance, allows buildings to have more floor area or additional height if they meet high levels of LEED certification. It’s these government incentives, rather than natural market forces, which are driving a lot of LEED adoption.
More generally, purely voluntary standards are at a high risk of gaming - since it’s the certification, rather than the actual healthy outcomes, that the owner is after, there’s incentive to have standards with very easy to achieve certifications that may not have much impact on health. We see this to some extent with LEED, where all developers go for the very easy credits (such as adding a bike rack), and avoid the more complicated to get credits.
The WELL standard that Allen and Macomber are enthusiastic about is illustrative here. WELL is a certification advanced by the "International Well Buildings Institute", which is in turn owned by Delos Living, a building wellness company started by former Goldman Sachs partners (and was in the news last year for a scandal that involved using political connections to sell New York schools expensive and poorly-performing air purifiers - whoops!)
WELL certification has gained ground quickly - though it was only started in 2014, it hit 4 billion square footage of certified space in 2022, and has now passed 4.7 billion square feet (compared to 24 billion square footage of LEED, which was started in 1992).
Like LEED, WELL has a tier-based system, with bronze, silver, gold and platinum tiers, with the higher levels requiring more credits (and more expense) to achieve. (The bronze tier seems to have been added later - it doesn't appear to exist in 2018). WELL also offers a "WELL Health and Safety" certification that was basically created to give buildings a certification that would allow them to reopen during COVID:
Achieving WELL Bronze, Silver, Gold, or Platinum is nontrivial to achieve, and requires real improvements to the indoor environment. For air quality, for instance, certification for an existing building requires it to have been tested in the last 5 years to ensure it meets ASHRAE requirements, along with a letter from an engineer verifying that fact. And that’s just a prerequisite - getting actual points require things like installing air quality monitors and displaying the information in a publicly accessible place. And getting the certification requires things like providing sensor data or performance tests to prove you meet the requirements.
The WELL Health & Safety rating, by contrast, is very easy to achieve (see appendix below) - most interventions do not require any substantial changes to the existing building, and instead require things like marking the floor to allow people distancing while in queues, having approved soaps and cleaning products, "assessing" various parts of the building, and meeting existing code requirements for ventilation. Determining whether the requirements are met is done entirely via evaluating written procedures.
The overwhelming majority of WELL certifications are the WELL Health-Safety certifications. Of the ~26,000 WELL certified buildings in the US WELL lists in their database, over 19,000 (close to 75%) are WELL Health-Safety. And of those remaining ~7,000, most don’t list any certification level (bronze, silver, etc.), which leads me to believe most of those are also WELL Health-Safety. Other data suggests that WELL Health and Safety is around 95% of North American WELL certifications.
WELL is pushing this certification quite hard, with televised commercials with high-profile celebrities advising people to "look for the WELL health and safety seal". Securing this seal is somewhat expensive (especially given the fact that, since achieving it is based on evaluating written documentation, there's no reason to believe that the cost of evaluation scales with number of locations).
So WELL seems more focused on selling the appearance of a healthier building. The actual, more difficult to achieve certifications that require the sort of interventions that Allen and Macomber advocate are vastly less popular than the easier to achieve one that still gets you a plaque you can put in your lobby and a note you can put in your ESG report.
The case for increased focus on building health, especially air quality, seems very strong to me. And I agree that creating better standards is an important step. But I’m less optimistic than Allen and Macomber that we can expect voluntary standards to do much work here. I suspect improving building health will require the long, slow work of getting building jurisdictions to require or incentivize it.
Appendix - How to meet WELL Health-Safety
Needs to meet a minimum of 15 out of areas (below are the easiest ways of meeting the requirements)
Support handwashing - provide soap, drying method, and signs to encourage
Reduce surface contact - provide an inventory of high-touch surfaces, ways to reduce touching, plan for implementing
Improved cleaning - develop a "cleaning plan"
Preferred cleaning products - using "low hazard", or "safer" eco cleaning products
Reduce respiratory particle exposure
queuing marks, separate entry and exit doors, and "strategies, rules, and communications" to reduce distance among occupants, and prominent signage
Develop emergency preparedness plan
Create business continuity plan
Plan for safe reentry/reopening
Provide emergency resources - first aid kits, AED kits, epipens, emergency notifications, etc.
Bolster emergency resilience - "designated space" for emergency responders (others, but this seems easiest)
Provide sick leave
Provide health benefits
Support mental health recovery (crisis counseling, etc.)
Promote flu vaccines
Prohibit smoking inside
Inventory air filters and UVGI systems, replace on manufacturers recommended schedule
Develop legionella management plan
Monitor air + water quality
Schedule inspections at mold, moisture risk locations (pipes, HVAC, etc.)
Promote health + wellness (? - very vague)
Restaurants must show health grades
In the Appendix, 5a should read “increase distance” rather than “decrease distance.”
Also in the Appendix, 19a is blank.
The idea that elevated CO2 reduces cognitive performance is far from convincingly proven. People spend months in submarines and space stations with high CO2 concentrations and still perform at a high level.
Many bedrooms reach at night higher concentrations then recommended for offices and we don't see any ill effects.
My parents' kitchen is poorly ventilated so I was worried and bought a CO2 meter. Despite frequent cooking the CO2 never reached dangerous levels.
Until I see strong evidence I'm going to treat this CO2 issue like just another manufactured scare. And keep my windows open throughout the summer.