This episode of the BS* + Beer show features Enrico Bonilauri, co-founder and chief product officer of EMU, and Cramer Silkworth, a licensed engineer and Passive House consultant, discussing HRVs and ERVs—their differences, mechanics, and applications.
Cramer kicks things off with a presentation titled “Introduction to ERVs and HRVs: Ventilation Without Taxation.” He describes the appliances as a means for ensuring good indoor air quality (IAQ) at close-to-room-temperature in a reliable way without incurring huge energy penalties. He shows us the inside of a unit and explains the way the intake and exhaust air streams move through the heat recovery core to remove stale air and deliver fresh air. He illustrates the principles of crossflow and counterflow, and points to the physical properties of an HRV core vs. those of an ERV core. (HRV cores conduct heat; ERV cores conduct heat and moisture.) He answers the question: Which do I need? Because moisture recovery in places that are cold/dry in winter, and hot/humid in summer is ideal, he says, “I think the entire eastern half of the United States would be best served with an ERV.” He also mentions a handful of manufacturers’ products—RenewAir, Panasonic, Zehnder, and Lunos—their price points, pros/cons, main features, and ideal applications. The second half of his presentation is about locating, installing, and ducting the units; what to think about when making selections; code considerations; commissioning; and client communications.
Enrico describes ERVs and HRVs as appliances for delivering fresh air. He talks about the need to balance systems, which is done by first, measuring the total intake and total exhaust, and then balancing individual registers to get the right airflow rates for each room. By way of clean and dirty Merv 13 filters, he illustrates the key to keeping running units properly, emphasizing that common but often-ignored refrain, “Change the filters regularly!” He also notes the difference a HEPA filter can make—a particularly relevant point in light of the current wildfires polluting much of the West Coast’s air. Unlike conventional construction, he says, which allows pollution to come in from nearly anywhere, supertight building envelopes offer more control—the point of entry is the HRV or ERV. Through a series of graphs and studies, he demonstrates the ways in which heat-recovery measurements can be inflated; and explains the need to insulate both intake and exhaust air supply ducts. He shows us different ducting materials, pointing out the pros/cons of each; stresses the importance of frost protection in new builds; and gives us a look at an installed unit in a 2×4 wall, noting duct sizes from the unit to the registers to the manifold.
The big takeaway? HRVs and ERVs deliver filtered fresh air—that’s all they are truly designed to do. But their nuances are many.
Enjoy the show!
Join us on Thursday, September 24, from 6 to 7:30 pm, when guests Bruce King and Chris Magwood of Ecological Building Network (EBNet) will launch our first book club discussion. The topic is The New Carbon Architecture: Building to Cool the Climate, which Bruce wrote and Chris contributed to. Hailed as a “paradigm-shifting tour of the innovations in architecture and construction” that promise carbon-sequestering solutions to the planet’s health crisis, this book ignites the environmentalist’s imagination. It also provides data-backed information on the many building products and methods at our disposal for combatting climate change. We plan to come to the show with a bunch of questions in hand—hopefully you will too.
Bruce King is the founder of the EBNet, and a registered engineer with 35 years of worldwide experience in structural engineering and construction. He is the author of Buildings of Earth and Straw, Making Better Concrete, Design of Straw Bale Buildings, ASTM International E-2392, earthen building guidelines, and dozens of papers and articles for conferences and journals. He has organized three international conferences on ecological building, and is the founder of BuildWell Source, a user-based collection of low-carbon materials knowledge, and of the BuildWell Symposia.
Chris Magwood is obsessed with making the best, most energy-efficient, carbon-sequestering, beautiful and inspiring buildings without wrecking the whole darn planet in the attempt. Chris is currently the executive director of The Endeavour Centre, a not-for-profit sustainable building school in Peterborough, Ontario. He has authored numerous books on sustainable building, including Essential Hempcrete Construction (2016), Making Better Buildings (2014) and More Straw Bale Building (2005). In 1998 he co-founded Camel’s Back Construction, and over a period of eight years, helped to design and/or build more than 30 homes and commercial buildings, mostly with straw bales and often with renewable energy systems.
-You can contact Kiley Jacques at [email protected].
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