I recently attended a Certified Passive House Training program at Yestermorrow Design/Build School. Along with the building science education, the computer modeling in Wufi and Therm, I really enjoyed getting to know the other people there. So, who attends an 8-day in-person course in Waitsfield VT? Energy geeks. Mostly architects, some HERS raters, students and two mechanical engineers.
As one of the two mechanical engineers there, and an energy geek, the Passive House (PH) standard appeals to me because unlike other green building standards, it’s performance based. Where other standards can feel restrictive, PH design is flexible – a project can achieve certification as long as it meets the energy and airtightness goals.
And those goals are no joke. To meet the PHIUS+ 2015 standards, a single family passive house in Boston could be looking at insulation values of R-43 for the wall, R-70 for the roof and R-20 below the slab. (The R-Values go way down in multifamily, because the surface-to-volume ratio improves.) The design principals used to meet the standards are: continuous insulation, air tightness, optimizing solar gains, heat recovery ventilation and minimized mechanical systems.
The mechanical systems approach for PH is refreshing: simpler is better. While the classical approach to PH uses space heating through ventilation ducts, this is not required, and in most cases it isn’t practical. Decoupling the heating and ventilations systems makes sense, because it keeps with the simpler is better design philosophy and because the demands on the systems are totally independent (ventilation is required at all times, heat isn’t).
My take-away from the course was that while the primary goals of the PH standard are energy efficiency, the results are greater durability, occupant health and comfort. By controlling the movement of heat, air, moisture and bulk water within the building, the outcome is a building that will last for generations.
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