PHIUS+2015 Climate-Specific Passive Building Standard

From Home Energy's July/August issue, written by Mike Knezovich, Director of Communications for PHIUS:

In March, Passive House Institute US (PHIUS) implemented a new climate-sensitive passive building performance standard. PHIUS+ 2015 gives designers and builders a simplified, cost-effective path to resilient, comfortable, net zero energy buildings.

The new metric generated healthy discussion in the existing PH community and has brought welcome excitement and fresh interest from newcomers. But there has also been misunderstanding and confusion.

It’s important to understand what’s changed, and what hasn’t.

PHIUS+ 2015 is a natural evolution for PH. It is not unprecedented. Switzerland, Sweden, and Belgium are among the nations that have adapted PH to their conditions.

The fundamental PH goals and principles are universal and unchanged:

  • PH drastically reduces energy consumption and carbon emission by reducing heating and cooling loads.
  • PH employs a systems-based, whole-building design approach.
  • PH is a performance standard (not a prescriptive checklist) with metrics that can be modeled and verified.

The PHIUS website provides a clickable map for users to find the performance metric for their specific climate. (PHIUS)

The design principles also remain unchanged:

  • A PH is superinsulated.
  • The building envelope is extremely airtight.
  • Windows and doors are all high-performance.
  • There is some form of balanced heat- and moisture-recovery ventilation and the smallest possible space-conditioning system.
  • Solar gain is maximized for heating and minimized for cooling.

Then & now

In the 1980s, two European scientists—Bo Adamson and Wolfgang Feist—refined the application of PH principles. (Feist went on to found the Passivhaus Institut in Germany.)

Feist’s work yielded a performance metric that marked the point where, in Europe, minimizing mechanical systems offset increased costs for the building envelope.

That metric was thought to be universal. The performance target (4.75 Kwh/ft2 annual heating load) would apply in Germany, San Francisco, Boston… It was a powerfully seductive idea: One world, one metric.

Fast-forward to today. PHIUS has certified and/or consulted on residential and commercial PH projects across North America and concluded: One size does not fit all.

In some cases, the European metric has led designers to make decisions that cause overheating. In others, they had to install prohibitively expensive levels of insulation. And cooling climates present a whole different set of challenges.

Market conditions can vary as widely as climate conditions. While the principles have proven to be universal, the performance metric has not. It served to get designers and manufacturers to push the envelope. But its limitations were confining PH to a niche.

That’s why PHIUS, in partnership with DOE and the Building Science Corporation, set out to optimize the target metrics for North America.

Three years of research modeled buildings across the continent, employing BEopt (see “Using BEopt to Optimize Home Energy Performance” on p. 24) and WUFI Passive, a PH modeling tool.

The work yielded a formula: Climate and other variables are input to generate efficiency targets that are aggressive, climate-specific, and cost-effective.

learn more

Download the full report, Wright, G., and K. Klingenberg. Climate-specific Passive Building Standards, BA-1405, Building America, March 2015.

Learn more about PHIUS+ 2015.

Still Passive House

It’s important to note that the PHIUS+ 2015 metric is an optimization of the European metric, not a relaxation. In fact, in some climate zones, PHIUS+ 2015 sets the bar higher, because until now, cost-effective energy savings were being left on the table.

To account for changing market conditions, available materials, and climate change, PHIUS will update the standard on a rolling cycle.

But passive house is passive house—the concept and principles remain the same.

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"But passive house is passive house—the concept and principles remain the same" umm sorry - no

Passiv Haus is Passive House - The older US version qualified but now it is PHIUS & yes it is a relaxation if you actually crunch the numbers: --- I am not saying it is not warranted but is completely different

Hi Sean,

Thanks for weighing in.

Passive house has always referred to a generic set of principles (super insulation, airtight envelope, erv, etc.) and a specific performance metric. The point was that passive house principles make sense universally and that remains unchanged (passive house is still passive house), but that a single performance metric does not make sense. Hence, he research on a standard that is climate sensitive. 

On that subject, while for cost effectiveness' sake, there are areas where the standard is "relaxed" compared to the euro-metric, there are others where it's actually more stringent. The idea was to hit a sweet spot in terms of conservation vs. say, addition of renewables. And that that sweet spot is necessarily different in different climate zones. And finally, that it will need to be revisited, and the standard reset, periodically. 

There is much confusion surrounding the Passive House standard, and unfortunately much of it has been generated by PHIUS.  No actual performance data has been shared by them to show that the international standard is not working here in the U.S., despite a growing body of evidence to prove that the existing standard is working remarkably well.  

Here's a link to an article by the University of Oregon, that looked at six Passive House projects in various regions of the country.  It concludes "The monitoring of these three houses helps verify the success of the German developed Passive House standard and it's potential within the range of U.S. climates."  DOE and Building America funded research on various other projects around the U.S. like this one here and this one here have repeatedly confirmed this same finding. (Conclusions in the Oregon NREL study: "As a design process, the Passive House process produces an extremely high performance design rooted in proven building science applicable to climate zones in the Pacific Northwest.")

While the PHIUS modification of the standard is certainly a welcome addition to the plethora of standards available on the market, the motivation for these changes is based in a political disagreement rather than any solid performance-based evidence.  PHIUS has yet to validate the claims of their new standard with a single measured performance or cost data analysis anywhere within the US. (I expect that may take some time.)  While PHIUS claims that the Passive House standard does not work in all US climates, PHIUS has curiously continued to certify projects for the past three years to the same metrics as the international standard.

As Sean Lintow suggests earlier in this thread, PHIUS would do well to rebrand and rename their offering.  Their PHIUS15 may well be a deviation or outgrowth of the original but it has become its own distinct animal.  It further requires the use of different software provided by another German Institute - Fraunhofer IBP.   

It's great to see the sister publication of this website, Home Energy Magazine, supporting the growth and dissemination of the original Passive House standard elsewhere.  It may be more helpful for everyone if the efforts to promote the PHIUS15 standard focus on its own merits rather than rely solely on the trashing an existing standard that is working well. 

To put it in simple terms, PHIUS is conducting a turf war, power grab, in the US. PHIUS does not wish to share the wealth but to control it. Too bad, in the end, we all wish to build better buildings...........terry

"It’s important to note that the PHIUS+ 2015 metric is an optimization of the European metric, not a relaxation. In fact, in some climate zones, PHIUS+ 2015 sets the bar higher, because until now, cost-effective energy savings were being left on the table." Well said Mike.

Some history and context is in order here - from a Canuck - to set you Yankees straight. Since when do Americans want anything to do with continental Europe anyhow - get off the couch, this is a "Made in America" standard. Get some back bone... oh, I guess Katrin's (that sneaky German turncoat that's going to make billions from this new standard) done that for you.

I have known about Passive House and Katrin's efforts to grow an industry around the European standard since the mid 2000's. I was part of a handful of attendees for her PH talks at Affordable Comfort and year after year, I saw the crowd grow. No one else was talking about it, so shame on all of you newcomers jabbering on and pointing fingers - the "passive house approach" to building needs unanimity and collaboration not this petty divisiveness. Build to what ever standard you want using the "passive house approach" and let the popularity and the utility meters do the talking once the occupant is in the build.

When Bush was in the White House, Katrin Klingenberg was pounding the pavement building a community in the USA around PH. She almost single-handheld did all the spadework in the USA so that the PHI standard could take root. Remember that; some of you were still in college getting pissed to the gills when she was toiling at conferences and spreading the word - work that doesn't pay much but fed her passion for the cause. If there's a Passive House movement in the USA now, its due to Katrin's bridge-building and elbow grease.

And this is where I as a Canadian am so embarrassed: a fellow Canuck was responsible for Katrin's hand being forced to develop a new standard. The divorce between PHI and PHIUS started right here in Canada. The division started in Ottawa and quickly snowballed to North America. The issues have been covered by both Martin Holladay of Green Building Advisor and Lloyd Alter in Treehugger and should be mandatory reading for all of you before you hitch your wagon to any one standard.

Did you read what Mike Knezovich says above? "Switzerland, Sweden, and Belgium are among the nations that have adapted PH to their conditions." and Americans (yes that includes Canada, Mexico and Peru) would be fools not to do the same.. unless you think the Swedes, the Swiss and Belgians are fools. Which is it? For the record, very few passive houses in Germany are certified, everyone knows its the "passive house approach" that counts.

This finger pointing drives me bonkers: the whole point of Passive House, is because of a global emergency driven by climate change in needing to build more efficient buildings now.  Katrin always said after her own build that the price needed to come down for wide adoption in the USA, she knows that culturally, Americans are different than Germans and she got it early on.

So stop the mudslinging, get the shovel out now and build. No more bickering and hair splitting, just build better using the "passive house approach". So let the race begin and may the best standard win.

Both standards are good. Both standards win. PHI knows how to build a PH in the USA.

The very nature of PH is about splitting hairs, but lets not split heads...........terry


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