Concentration of CO2 in the Atmosphere

The Great Indoors: Creating a More Healthful and Safer Built Environment

Multiple Contributors from Steven Winter Associates

With the spread of COVID-19 has come widespread quarantine, work-from-home policies and increased time indoors, making it all the more important that we think about the air we’re breathing and the surfaces we’re touching. With certain building and design considerations, we can make these impacts beneficial.

Here’s some timely information from Steven Winter Associates’(SWA) experts on the considerations ensuring the health and comfort of a building, and on the certifications that assure these considerations are met.

Filtration and Ventilation

One of the keys to a healthful living environment is high quality indoor air achieved through ventilation.

Simply put, ventilation removes contaminants that accumulate in the indoor air and replaces it with outdoor air that is not contaminated. There are several ways to ventilate. Most buildings have exhaust-only ventilation systems, characterized by local mechanical exhaust fans, operated intermittently, which typically remove air from the kitchen or bathroom. Replacement air is pulled into the living environment from an adjacent corridor, an open window, or your neighbor’s apartment. It might be pulled through the wall assembly, the crawl space, a crack in the foundation, or some combination of the above. And, who knows where that air has been?

There is a better way. Continuous balanced ventilation systems, combined with air sealing and compartmentalization, provide more control over the air we breathe. Air is constantly exhausted from the kitchen and bathroom at low volumes and is replaced with air from a known origin via a dedicated outdoor air duct. The living environment is pressure-balanced – there’s an equal volume of supply air and exhaust air. Our air is no longer being pulled from parts unknown. Balanced ventilation systems operate best with the installation of a continuous air barrier system in exterior wall assemblies, and compartmentalization measures between apartments, decreasing the amount of air that is pulled from adjacent apartments and through wall assemblies. Additional benefits include decreasing transmission of odor, smoke, sound, and pests. With a continuous balanced ventilation system, and the appropriate compartmentalization and air sealing measures, we know the origin of our breathing air.


Thermal comfort – favorable temperature and humidity conditions – is fundamental to the proper functioning of any occupied space and wellness. Indoor environments that are too warm may lead to sick building syndrome resulting in occupants’ negative moods, increased heart rate, respiratory symptoms, and feelings of fatigue. Relative humidity below 20% can cause dry eyes, skin, and mucous membranes. High relative humidity (above 70%) may lead to stuffiness or mold and fungus growth, which produce allergens, irritants, and in some cases, potentially toxic substances (mycotoxins). Regular inspections of roofing, plumbing, ceilings and HVAC equipment will identify possible sources of moisture and potential condensation, which should be immediately addressed.

Of interest now, viruses survive for longer periods at low humidity, so it is even more important to maintain relative humidity between 40% and 60%.

Building Materials

The current pandemic brings us a renewed awareness of the materials in our environments. Thoughtful and responsible choices can help increase our health and wellness as our living spaces become full-time work, education and play spaces.

There are choices for current and future buildings. Think about cleanability. How easy or difficult is it to disinfect a given material with soap and water or disinfectant? (“Green” cleaning protocols would not ordinarily include bleach or chemicals.) How many grout lines or other transition materials are used, how cleanable are those transitions, and can we choose materials that minimize those transitions? We expect to see a renewed focus on cleanable materials that will ultimately improve health and durability under ordinary circumstances (and extraordinary circumstances).

Keep on the look-out for a surge in anti-microbial finishes. Be careful with those, because while they are designed to kill or inhibit the growth of microorganisms, many antimicrobials contain triclosan and triclocarban, which have been shown to interfere with normal human development and function.

Another concept to consider is no-touch building finishes and amenities. In a post-COVID-19 world, choosing touchless automatic door openers and elevator buttons, more lighting occupancy sensors, touchless water-bottle refill stations will be on the rise. Those touchscreens in the lobby or checkout counter will likely be a thing of the past. We hope that there will be a touchless handwashing station in every new building lobby!

Universal Design

The goals of Universal Design include incorporating health and wellness into the built environment. Many of the concerns targeted in health and wellness design strategies, such as chronic respiratory disease, diabetes, heart disease, and chronic illness, qualify as disabilities under the Americans with Disabilities Act (ADA). Further, each one of these health concerns is an underlying condition highlighted by the COVID-19 pandemic.

There are several shared goals and design strategies among health and Universal Design initiatives that not only serve to create healthier environments but can also contribute to better spaces for all building occupants.

A living rooftop design. Images courtesy of Steven Winter Associates.


Knowing what to design and specify is the first step. Proper construction and installation are next. But to really ensure that buildings are constructed for health and wellness, the final step is certification. Here are a few programs.

WELL: Created by the International WELL Building Institute (IWBI), the WELL Building Certification Program is focused on human health, mental wellness, community engagement, and overall comfort and well-being.

The IWBI requires on-site performance testing verification by third-party testing agents to prove that the project’s design and installed materials match the requirements as prescribed. On-going performance verification is required every three years.

Fitwel: The Center for Active Design oversees the Fitwel certification systems for healthy buildings and communities. Probably the most powerful and unique elements of the program are not the indoor air quality plans but the ways the program addresses the connection between physical inactivity and mental health. Fitwel includes daylight, views of nature, operable windows, a vegetable garden to plant, or acoustic comfort from exterior or interior background noise. For more ideas about what can you can do to make your current or future project a bit healthier, visit the Fitwel Resources page:

Indoor airPLUS

Created by the US EPA, Indoor airPLUS Construction Specifications require that a newly built home includes additional protections to address moisture control, radon resistance, pest prevention, improved HVAC systems, reduced combustion pollutants, and low-emission materials. As an added layer, all Indoor airPLUS homes must first earn ENERGY STAR certification, improving energy efficiency and comfort as well. For more information on this certification, visit the EPA website:

Steven Winter Associates, Inc. provides research, consulting and advisory services to improve commercial, residential and multifamily built environments. They specialize in energy, sustainability and accessibility consulting as well as certification, research and development and compliance services.

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