Healthy spaces, particularly through LEED certification, have come into focus for designers, developers, and homeowners alike
By Larissa Oaks and Emma Hughes
High-performance, green homes provide a host of benefits for their occupants: cleaner indoor air, ample natural light, and reduced energy and water bills. The average monthly electric bill in the United States is $117, with heating and cooling accounting for about 32% of electricity consumption. Green homes use less energy and help families lower those utility payments. High-performance, green homes may also be constructed with resilience in mind, and be better able to withstand the impacts of extreme weather events such as floods or hurricanes.
While consumers generally understand the environmental and economic benefits of high-performance homes, the human health impacts of these structures are not always acknowledged. With more individuals spending increased amounts of time at home amidst the global pandemic – and many companies reevaluating their telework policies – the importance of healthy residential spaces has come into focus for designers, developers and homeowners alike. By leveraging an integrative design process and understanding trade-offs between building energy consumption and ventilation, developers can deliver homes that promote human health while saving energy, water, and money.
The LEED residential rating systems provides a framework for developers to maximize triple bottom line benefits and balance human health and environmental priorities. On average, LEED-certified homes use 20–30% less energy than a home built to code, with some homes reporting up to 60% in savings. Reduced energy use translates into lower utility costs and increased savings for the homeowner or tenant. Energy efficiency is one of the most effective strategies for mitigating climate change and it also reduces the need to build new energy generation infrastructure, the pollution from which disproportionately impacts the health of disadvantaged and vulnerable populations.
In addition to lessening the environmental impact of day-to-day life, high-performance green homes can directly promote or impede occupant health outcomes. According to the Environmental Protection Agency, concentrations of some pollutants are two to five times higher indoors than outdoors. Many energy efficiency measures such as additional insulation and reduced infiltration can further increase the levels of indoor pollutants if proper indoor environmental quality features are not also included and used in the home. Homeowners and renters play a critical role and must be educated about the best ways to operate and maintain their home to optimize indoor air quality. Designers and developers are responsible for selecting intuitive systems that will be actually used by the occupants. In one case, according to research on homes constructed in California between 2011 and 2017, and therefore constructed to meet the mechanical ventilation requirements per California Title 24, many homeowners may not be regularly operating their mechanical ventilation fans and the ventilation system controls did not have sufficient labeling for proper use.
In addition to lessening the environmental impact of day-to-day life, high-performance green homes can directly promote or impede occupant health outcomes.
Achieving energy efficiency goals in a way that also improves indoor air quality can be accomplished more readily with the use of rigorous verification as required in LEED. Many things can go wrong in the construction and installation phases of a home that could compromise the expected energy savings and indoor environmental quality. LEED certification is invaluable in ensuring that throughout the construction process and before handoff the home performs to the design specifications. The homeowners and renters will be main benefactors of this additional verification and level of quality.
LEED-certified homes require sufficient ventilation and prioritize strategies and materials that minimize exposure to pollutants that can negatively impact human health. This includes employing source-control strategies targeted in areas of the home where there may be potential for higher pollutant levels, such as kitchens and garages. Controlling pollutants at the source is more efficient and ensures indoor air quality is not degraded elsewhere in the home. According to a Rocky Mountain Institute report, gas stoves can emit elevated indoor nitrogen dioxide levels often exceeding indoor guidelines and outdoor standards, and can have levels 50% to 400% higher than homes with electric stoves. Installing range hoods in the kitchen that exhaust to the outdoors can prevent this nitrogen dioxide and other pollutants produced from cooking from leaving the kitchen and entering the family and bedroom areas. Given the amount of pollutants produced when cooking, even on electric burners, kitchen exhaust to the outdoors is a minimum requirement for all LEED homes. Recirculating range hoods or recirculating over-the-range microwaves do not satisfy the kitchen exhaust requirements. Additionally, efficient HVAC systems that bring filtered outdoor air inside can further protect a home’s occupants.
Strategies promoting human health are incentivized through credits in LEED and many are found in the rating system’s Indoor Environmental Quality credit category, including:
• Prerequisites related to ventilation, air filtering and environmental tobacco smoke that ensure minimum levels of indoor air quality.
• Prerequisite combustion venting and credits related to enhanced combustion venting, garage pollutant protection and radon-resistant construction ensure a reduction of combustion gases, soil gas contaminants, and other pollutants in the home.
• Low-Emitting Products credit that reduce occupant exposure to volatile organic compounds (VOCs), which emit from common building materials and finishes. VOCs can cause eye, nose and throat irritation, headaches, damage to liver, kidney and central nervous system, and may cause cancer.
• Balancing of heating and cooling distribution systems encourage systems that improve energy performance and comfort.
USGBC’s interactive infographic on its website provides further details on the ways that residential projects can promote occupant wellness. As the industry continues to navigate through the pandemic, building green is at a forefront, not only because it is cost effective for homeowners, but because it contributes to a healthier lifestyle.
Larissa Oaks is USGBC’s indoor environmental quality specialist and helps manage the technical development and maintenance of LEED’s Indoor Environmental Quality credit category. Emma Hughes is a LEED project manager at USGBC and manages the technical development of LEED credits related to water efficiency and energy. She also leads the development of the LEED Zero certification program.