Building science and the home energy performance revolution

 

Passive House diagram (courtesy 100khouse.com)

BY ZACK SEMKE

Editor's note: In full disclosure, this post was written by an employee of Hammer & Hand, a Portland Architecture sponsor. But is not intended as an advertorial. Rather, it was decided that the company's pursuit and promotion of Passive House technology would be relevant to readers and, because one of Hammer & Hand's leaders also leads the nonprofit Passive House Alliance, part of a broader exploration.

As I've watched our home performance team conduct dozens of home energy performance audits and home energy retrofit services in recent weeks, I've been reflecting on how different the green building landscape is now versus just 15 years ago.   What's changed?  Our understanding of building science: how a building's various components interact with one another in a holistic system.

Today, building science experts are transforming the field of home performance energy audits and retrofits.  Backed by a rigorous understanding of building physics and dynamics, advanced building scientists can model, design and implement home energy retrofits that eclipse yesterday’s home energy efficiency improvements.

“The field of building science has grown up and is now driving reductions in home energy consumption that would have seemed impossible ten or twenty years ago”, explains Sam Hagerman, co-owner of Hammer & Hand, and President of the national nonprofit, the Passive House Alliance.  “The best building science technicians know how to harness this new power to the benefit of clients and the planet.”

The typical home performance technician not trained in advanced building science is forced to rely on a boilerplate approach in the field, applying prescriptive retrofit solutions aimed at satisfying the requirements of the latest governmental weatherization program.  While this approach does achieve some reduction in home energy consumption, it falls short on two counts: it squanders money on prescriptive home energy solutions that may not address the unique problems of a given home; and it results in energy retrofits that will likely become obsolete in 10 or 15 years, or whenever the next weatherization program comes along.

Advanced building science, on the other hand, revolutionizes home performance audits and home energy retrofits because it empowers the building scientist to optimize homes through a performance approach, using sophisticated modeling to tweak air tightness, insulation, ventilation and other building component variables to design the most cost-effective home energy retrofit possible for each unique home.  This leads to better solutions with bigger return on investment, and energy efficiency gains that are well ahead of the curve – retrofits that will stand the test of time.

“Everything is about optimizing”, says Skylar Swinford, Certified Passive House Consultant and building science team leader at Hammer & Hand.  “Take heat recovering ventilation systems, for instance.  I love HRVs because they conserve energy that would otherwise be lost in a home’s exhaust air.  But when we do the math, if the building science tells us that super-insulation is a more impactful investment for a given home, then we prescribe that ahead of an HRV, and switch to a more basic continuous mechanical ventilation system.  Each variable is scrutinized and fine-tuned for optimal performance.”

The Passive House movement, widely recognized as representing the cutting edge of building science and home energy performance, is a potent source of building science expertise for our leading building analysts and technicians.  So it’s no surprise that today’s most successful energy retrofit measures come straight from the Passive House high performance playbook, like:

• Aggressive air sealing to create a nearly airtight building shell.

• Continuous mechanical ventilation to provide constant flow of fresh air – often a heat recovering system for better energy performance.

• Intensive, high quality insulation, with low global warming potential – usually cellulose or water-blown spray foam.

• Computer modeling to optimize the performance and value of the home energy retrofit package.

“When we are smart about home energy performance audits and retrofits, and bring advanced building science to bear,” says Hagerman, “it’s a win for each individual client who receives better home performance for the money – greater comfort, safety, and energy savings.  But it’s also a win for society at large, because we’re taking full advantage of every retrofit to significantly reduce the energy consumption of our built environment.”

And that’s important if we hope to make a dent in global climate change or achieve energy independence and security.  Roughly half of US energy demand comes from buildings and the building sector.  And each time we don’t maximize the potential of an energy retrofit, we’re missing a critical opportunity that might not come along again for a long time.  After all, if we deliver an inadequate energy retrofit to a homeowner once, do we really expect that person to have the appetite for another retrofit any time soon?

We need to do it right the first time.  Fortunately, the building science is now there to make that happen.

Zack Semke is Director of Business Development and Chief Evangelist for Hammer & Hand

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Comments

[Insituarchitecture.wordpress.com]

Amen! The translation of Passivhaus to Passive House is unfortunately misleading, as this approach applies just as well to commercial and multi-family buildings. Although the issues and solutions are often more complex than single-family homes, the opportunities are enormous and our efforts should be focused across building scales.