How often have you walked into your own home and noticed a specific smell? Does that ever concern you? It's worth paying attention to, as indoor air quality has a significant effect on your health. Rule #1: Clean air has no smell, so that's the goal.
Have you been following along with our LEED for Homes series? If so, you may have already read about many of the best practices of making your home more sustainable. Since "sustainability" is such a massive topic, we've broken it down into manageable components: Location & Transportation, Sustainable Sites, Water Efficiency, and two under the Energy category (prerequisites and credits). Last month, we looked at what is arguably the most interesting section, Materials & Resources.
Given how much time people are now spending at home, today's topic is perhaps the most important and timely: indoor environmental quality—or in other words, a healthy home.
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By Melissa Rappaport Schifman, Editor-At-Large
Feb 11, 2025 · 7 min read
According to the US Environmental Protection Agency (EPA), concentrations of some pollutants indoors can be two to five times higher than outdoors. This reality is due to several factors, including tighter, more energy-efficient building envelopes, chemical usage from cleaning supplies and pesticides, and growth in synthetic home furnishings and building materials. Polluted indoor air can be unpleasant by itself. Still, more concerning, it can cause adverse health effects such as respiratory disease, headaches, fatigue, and irritation of the eyes, nose, and throat—and, in the case of more dangerous pollutants like radon, cancer.
I think about indoor air quality in terms of three pillars. It all begins with what might be contaminating your air in the first place, so we'll look at reducing the source of pollutants. Next, assuming you can't control all contaminants, it's important to ventilate your indoor air. And finally, air filtration helps decontaminate your air. LEED addresses each of these with various prerequisites (the most important components when building a remodeling a home) and credits, so let's dive in.
A single-family home with an attached garage may seem like the utmost in luxuries—you don't have to go outside to get into your car and do the multitude of other activities people tend to relegate to the garage. The problem? Most cars are still gas-powered, and when running, they produce the deadly gas carbon monoxide. To protect homeowners, LEED requires that no air-handling equipment or ductwork be located inside the garage (unless it is only serving the garage).
In addition, all shared surfaces between the garage and the home must be tightly sealed. All connecting floor and ceiling joist bays must be sealed, and any doors into the garage must be weather-stripped, as though it is an exterior door. These measures help protect conditioned spaces from carbon monoxide emissions and other harmful odors, like paints and chemicals stored in the garage.
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Melissa became the Twin Cities’ fifth LEED for Homes Accredited Professional (LEED AP) and completed the work necessary to get her own home LEED Gold Certified, the basis for her book, Building a Sustainable Home: Practical Green Design Choices for Your Health, Wealth, and Soul, (Skyhorse Publishing, August, 2018). With her corporate experience in finance, marketing, and business development, and an MBA and Master’s in Public Policy from the University of Chicago, Melissa has been providing sustainability advisory services to businesses, governmental agencies and non-profits, focusing on strategic and operational change that provide bottom-line financial returns. She has led the LEED certification of two million square feet of commercial buildings, written GRI-compliant Corporate Sustainability Reports, is a LEED Pro Reviewer and LEED mentor with the U.S. Green Building Council. She is the founder of Green Intention LLC where she writes about sustainable home living.
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Air pollutants can come from many different places. The LEED rating system starts with two prerequisites that limit the two most deadly pollutants: carbon monoxide from a car in the garage and radon. (We shouldn't have to say this, but eliminating exposure to tobacco smoke might be step one.)
Radon is an odorless, colorless, radioactive gas. According to the EPA, radon is the second leading cause of lunch cancer after cigarette smoking. While radon is naturally occurring, the good news is that homeowners can limit exposure by addressing it early in the home's construction. And, it may only cost between $250 and $750, depending on the location and size of the house.
The first step is to check if your house is located in a higher-risk zone. If you live in a high-risk area, you'll want to make sure you follow radon-resistant construction techniques, which you can find on the EPA website or in the LEED prerequisite documentation.
The basic tenants include providing:
For existing homes, read more about radon testing and mitigation.
Note: any home that earns the Environmental Protection Agency's (EPA's) Indoor airPLUS label automatically meets these LEED prerequisites. You can learn more about it from Rise here.
After controlling for those deadly indoor air pollutants, LEED awards points for going the extra mile by preventing not-so-deadly contaminants and ensuring only low emitting products enter the house.
A house can earn LEED points—and be a healthier home—by reducing exposure to indoor airborne contaminants like dirt, dust, pollen, and other allergens. How? Here are some reasonably easy tactics:
The number of products and furnishings that enter your home is astounding, and trying to stay on top of whether or not they are harmful to your health can be overwhelming. To narrow it down, the two main things to avoid are volatile organic compounds (VOCs) and formaldehyde. And the primary places to look are in paints and coatings, adhesives and sealants, insulation, and flooring (all types—including engineered wood, carpeting, and padding).
Many products—such as stone, ceramics, glass, unfinished/untreated solid wood, and concrete—are inherently non-emitting, so those are better choices. When you start adding paints, varnishes, engineered wood, and particleboard, you need to pay more attention to what you're buying. To ensure you're not bringing unhealthy products into your home, look to the manufacturer to ascertain that their product meets VOC content limits. (This gets a little technical, but for more information, see the California Air Resource Board (CARB) or the South Coast Air Quality Management District (SCAQMD) Rules). For formaldehyde in composite wood products, ensure the product meets the EPA Toxic Substance Control Act (TSCA) Title VI.
So now you've done all you can to prevent pollutants from getting in your in the first place, but it's not possible to be completely contaminant-free. Daily activity in kitchens, showers, and bathrooms can create moisture problems and exposure to other pollutants. So you'll want to make sure your home is well ventilated.
For whole-house ventilation, LEED v4.1 requires that a home complies with building code—specifically, sections 4, 6.7, and 6.8 in ASHRAE 62.2-2016 (with errata), or your local building code, whichever is more stringent. If your area has a less strict building code, you may want to talk with your HVAC installer about minimum airflow requirements. (Note that LEED v4.1 upgraded from ASHRAE 62.2-2010 in prior versions, so it is more stringent.)
In addition to whole-house ventilation, LEED requires "local exhaust." This requirement means that you need to install smaller mechanical exhaust systems like range hoods in the kitchen and bathroom fans in all bathrooms, according to ASHRA 62.2-2016, sections 5 and 7. These exhaust systems need to be vented directly outdoors and be ENERGY STAR rated. Over-the-range microwave ovens do not meet the requirements, as the exhaust just gets recirculated.
The third component of ventilation relates to "Combustion Venting"—ensuring that any appliance that burns fuels for cooking or heating must be installed with power-vented exhaust or closed combustion (i.e., sealed supply air and exhaust ducting). Why? Gas-powered appliances such as furnaces, water heaters, and clothes dryers emit harmful emissions when in use. Exposure to combustion pollutants can lead to headaches, dizziness, and difficulty breathing, and even death from carbon monoxide poisoning. For this reason, LEED v.4.1 (and building code) requires that you install carbon monoxide detectors on each floor. (Learn more about combustion venting.)
Filtering your air is the third pillar of healthy indoor air in your home. If you have a mechanical ventilation system, the minimum air filtration requirement is MERV 8. The higher the MERV rating, the more pollutants are removed from the air. If you don't have a whole-house system, consider some portable air purifiers.
The three pillars of healthy indoor air are:
Each of these complements one another to limit exposure to unhealthy VOCs, gases, formaldehyde, and other pollutants that can cause respiratory illnesses. The LEED section on Indoor Environmental Quality might be the most critical component of a sustainable home. After all, if you don't have your health, it's hard to focus on saving energy, water, money, and the bees!
