Finding a natural solution
Mark A. Miller is a practicing architect/builder/developer living in Chicago who designs projects around the country. His studio, Mark A. Miller Architects + Builders, designs and builds high-performing, energy-efficient homes that speak to the soul. Mark recently co-founded the Passive House Alliance Chicago and is lecturing about the Passive House standard throughout the Midwest. You can learn more about his unique approach to designing thoughtful homes at his websites: Zen + Architecture and Passive House Midwest.
A fellow architect recently interviewed me for another blog and I would like to share this conversation with you as an introduction to the Passive House standard.
Q: What makes a Passive House different from a conventional house?
A Passive House keeps its conditioned air "in" and the unwanted, unconditioned air "out". This means paying extra attention to the quality of detailing in the building's shell:
• Super-insulated walls
• High-performing triple-glazed windows, with many seals and locks
• No pipe penetrations in the exterior wall
• No kitchen or bath exhaust fan roof caps letting cold air into the house
• An air tight layer stopping wind-driven moist air from getting into the shell
• Use of an energy recovery ventilator (ERV) or heat recovery ventilator (HRV), operating 24/7, to continuously remove stale air and bring in fresh outside air, while "recovering" 85 percent of the heat energy that would be exhausted, and returning that energy to the incoming air
• No conventional furnace
These details can reduce energy bills by up to 90 percent of a conventional home’s energy bills!
Q: As a self-described green architect, how do certified Passive Houses compare to your other homes in terms of energy efficiency and sustainable design aspects? How is the design and construction process different?
At the moment, Passive Houses seem to be the best energy-efficient design strategy that uses conventional building components; it outperforms just about everything. The theory is simple—reduce the home’s heating and cooling needs, and you’ll hardly need to produce any conditioned air. This concept can be applied to many aspects of life: finances, shopping, vehicle fuel economy, etc. It's a universal theme.
The construction process is similar to my other green projects, but I pay greater attention to how the building materials are assembled: no gaps in the insulation; no pipes in the exterior walls; no thermal bridges (a building component that assists heat energy getting from the exterior to the interior or vice-versa). Insulation levels are typically double-code requirements, depending on exact climate. I also pay extra attention to window types, sizes and locations on the envelope.
Before insulation gets installed, it's also recommended to do a blower door test, to understand how air-tight the shell is. This provides an opportunity to walk around the house and seal up any areas where you can hear and feel air rushing in. Then, with insulation and drywall, the air-tightness gets even better. This is not done with conventional home building.
Q: Certified Passive House structures have been appearing in the news a lot lately, but people have building passively for years. What's the difference, if any, between Passive Houses and passive solar houses?
When folks hear the phrase “Passive House,” most think this is a “Passive Solar House,” but these are two different techniques. A passive solar home attempts to maximize solar heat gain throughout the day mainly through abundant south-facing glazed windows. Passive solar houses then attempt to store this heat into building components such as concrete floors, water tanks or trombe walls for use at night.
On the other hand, a Passive House is less concerned about maximizing and storing passive solar heat gained during the day, but focuses instead on keeping whatever heat that is produced within the home in the house. Passive Houses focus more on the quality of the thermal envelope—and this is why many Passive Homes can be comfortably heated with just a 1000w hair dryer!