As described in A Builder's Guide to Breathable Indoor Air, current building codes require ventilation rates based on energy and comfort concerns, rather than as a basis for creating a healthy indoor environment. Our recommendations for health-based ventilation rates (see table below) are based on having designed thousands of systems using high performance ERV's, and on personally living in a 5-bedroom home with a high-performance ERV for 6 years.
Our recommendations also take into account data from 80,000 Hayward Scores demonstrating acceleration of self-reported health symptoms in smaller homes with high occupancy. The Hayward Score tracks 23 medical symptoms associated with homes, and it is currently the largest study on health and housing ever created.
The comparison of ventilation rates in the chart below underscore the fact that health-based ventilation rates must be based on occupancy number, rather than house size. This is especially evident in smaller homes, suggesting that, while likely unintended, current ventilation standards discriminate against smaller, typically lower income, residences.
Ventilation air must dissipate or remove human microbial shedding, which includes skin cells, to maintain a healthy indoor environment. The latest research from Indoor Chem demonstrates a high impact of human skin cell shedding with occupancy higher than two.
We welcome comments, data and information about other studies to enlighten our recommendations. Please send to: [email protected]
Bill is CEO and Chief Sustainability Officer of Hayward Lumber, a 100-year-old California lumber and building material supplier. To accelerate the industry's commitment to sustainable forestry, he chaired the board of the Forest Stewardship Council US from 2005-2010. Inspired by a horrific personal experience in an unhealthy home in 2009, he developed the Hayward Healthy Home Principles and founded the Hayward Score to educate and empower consumers to live in and demand healthier homes. Having scored over 80,000 homes, his team has developed the largest study available correlating self-reported symptoms with housing characteristics and occupant habits. His goal is to demonstrate the business case for all dwellings to be healthy, durable and energy efficient.
Mark LaLiberte is the Chief Business Development Officer for Hayward Companies, based in Monterey, California. His goal is to bring innovation, technology, and sustainable processes to the Hayward Company and its collection of businesses. Our mission is to provide the dissemination of information about research, performance improvements and innovative ideas to a regional group of talented builders, architects and developers. It is Hayward Lumber's goal to deepen it’s position as a leading supplier of building materials. Mark has been involved in our industry for over 35 years. He is the co-founder of Construction Instruction, a Denver, CO based company dedicated to research and educational dissemination with 20 years of national and international experience. He helped develop the Ci App to provide easy access to thousands of videos, documents and links to assist the building industry in finding creditable information and innovative installation methods.