A passive house at dusk, the design is modern and angular. The building is taking advantage of the climate in the area it was built in order to reduce energy consumption needs to run it.
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Take advantage of nature

What is a Passive House and Should I Build One?

Steve Hansen
October 4, 2023

For most of us, housing is a major expense. That’s ok, because owning a home is usually an investment, as well as providing a place for us to live. Ongoing costs for homes that are not energy efficient, though, can be challenging or at least irksome. Is there a better way?

There definitely is. How would you like a house that costs roughly 5% more than a “standard” house and uses only 10–20% as much energy for heating and cooling? Or that is actually net-zero or net-positive in energy use? It’s possible, and those homes exist today. They’re called Passive Houses.

The History of Passive Houses

Passive houses were first developed and tested in the frigid regions of the U.S. and Canada in the 1970s. The main idea was to superinsulate and air seal the house to minimize the need for heating and cooling. They didn’t take off in North America at that time, but in the 1990s, German physicist Dr. Wolfgang Feist used those same ideas to develop the Passivhaus standard. Building geeks in the U.S. took notice.

One of those geeks was architect Katrin Klingenborg, who built the first Passivhaus in North America for herself in 2002 in Urbana, Illinois. From there, she founded the Passive House Institute US, now just called Phius. Since then she’s continued to work on developing the methods, materials, and workforce to get passive buildings constructed for our unique conditions in North America.

The Phius standard is not just for houses anymore, either. Phius offers a few certifications that apply to retrofits, multifamily buildings, office buildings, schools, and just about any other human-centered space.

Principles of Passive Building

For the most part, the Phius approach is a rigid, performance-based system. It’s less focused on material choices than LEED, for example, which is a points-based system. Here are the principles that all passive buildings adhere to, according to Phius:

Thermal control

Passive buildings require a high-performance enclosure using continuous insulation to maximize comfort and energy efficiency. Thermal control also requires eliminating thermal bridging, which happens when a building material conducts more heat or cold than the materials around it. This can lead to interior condensation and mold growth, as well as “cold corners” and decreased comfort.

Air control

Two factors contribute to air control: air tightness and balanced ventilation. Certified passive buildings must meet a standard and pass a test for air tightness. In addition, all passive buildings must have an active ventilation system with an energy recovery ventilator (ERV) or a heat recovery ventilator (HRV). These devices run continuously and supply fresh, filtered air while they exhaust the stale interior air (more on those here).

Radiation control

This requirement refers to solar radiation. The tactic uses high-performance double-pane and triple-pane windows and doors and carefully controls their sizing and orientation to minimize the need for cooling. Another tactic uses shading strategies to capture solar energy in the heating season while minimizing solar gain in the cooling season.

Moisture control

Along with air control, moisture control is crucial in an ultra-tight house. This will include building design for vapor control, as well as the choice of mechanical systems, such as the ERV/HRV mentioned earlier, and possibly additional components.

Phius Certification

Phius now certifies projects, products, and professionals to help anyone with their passive building project. Why would you need or want certification? For your own home, you can locate a certified passive building professional to work with you on your project. This includes:

  • Phius Certified Consultant: this might be the designer(s) for your project.
  • Phius Certified Builders: find a builder skilled and knowledgeable in passive building techniques.
  • Phius Certified Rater: these individuals are involved in third-party inspection and testing, such as blower-door testing, and confirming that your project meets Phius standards.
  • Phius Certified Verifier: these individuals work primarily with multifamily projects.

Certifying your project offers some advantages, as well. Working through the certification process offers another level of iterative design and quality control that contributes to a higher standard overall. And when you’re finished, you’ll have a Phius-certified home, which has value if you ever decide to sell.

The certified product database has more than 700 products. Currently they include doors, windows, skylights, and prefabricated panel systems. These certified products are a handy shortcut for design professionals, who can choose them knowing they meet passive building standards.

The Phius Building Standards

For new residential construction, Phius uses two building standards: CORE and ZERO. CORE is the evolution of the original passive building standard, and ZERO is a newer standard focused on net-zero buildings.

Phius CORE

In addition to the principles I mentioned above, Phius CORE has a few more factors to consider.

Active conservation

This idea addresses minimizing overall energy usage with efficient appliances, lighting, and mechanical systems. The Phius standard spells out a “Source Energy” target that’s part of the design modeling, so at the design phase you’ll have an accurate model of the electricity requirements for your home.

Renewable energy

The CORE standard doesn’t require any renewable energy generation from your project, but you do get some credit for onsite generation.

Electric vehicle charging infrastructure

For projects where parking spaces are included, you’re required to include an EV charging station and possibly more than one, depending on your project. One-family and two-family homes must have one EV-ready space. For multifamily projects, you’ll need to consult the Certification Guidebook.

Combustion and fireplace safety

Combustion of any kind in a tightly sealed house is risky. The CORE standard permits fossil-fuel appliances, but all heating and water heating systems must be sealed, direct-vent units. Fireplaces and woodstoves are permitted only if they have an airtight firebox and dedicated combustion air inlet.

On-site inspections

A Phius certified third-party rater will be making frequent visits to your project site, as he or she will be inspecting a number of building assemblies and performance metrics. That could include foundation and pre-drywall inspections, whole-building airtightness inspections, and hot water, heating, and cooling distribution systems testing. Probably many more.

Electrification readiness

Even though fossil-fuel appliances are permitted, the home must be ready for electric equivalents. If you choose a gas range, water heater, or clothes dryer, the CORE standard requires that wiring for their electric replacements be included in the build.

Phius ZERO

Taking Phius CORE to the next level, Phius ZERO modifies the combustion and fireplace safety component and adds a renewable energy requirement.

Renewable energy

You’re required to incorporate renewable energy into your Phius ZERO project, and it can be on-site or off-site. Two great options include rooftop solar panels and buying into community solar. The Certification Guidebook has more information.

Combustion and fireplace safety

Under Phius ZERO, you can still have an airtight fireplace or woodstove with a combustion air inlet, but no other combustion is permitted. No gas ranges, gas water heaters, or gas clothes dryers are allowed.

Should You Build A Passive Home?

If you’re considering building a home, you should do what works best for yourself and your family. But for a tiny cost premium of 3–5% upfront and ongoing savings that could be 100% of your current utility bill, I’d say it’s worth considering. Plus, most passive home owners say their homes are so much more quiet and comfortable than their previous homes. They don’t hear the furnace and AC switch on. They don’t hear traffic when the windows are closed. The temperature and humidity stay constant. And they pay little to nothing for utilities! What’s not to like?

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