Notes from the Frankfurt Conference

The impetus for my journey to Frankfurt, Germany in April was the 17th International Passive House Conference. As I walked toward the venue it occurred to me that this is my 10th anniversary at that event…

…and that we’ve come a long way on this side of the pond. It looks like we might be able to match participation this year at our upcoming 8th Annual North American Passive House conference in Pittsburgh. Overall participation in Frankfurt, according to the distributed participants list, was 650 people.

CompacFoam

Ninety exhibitors were on the exhibit floor. Among those were quite a few very large companies such as Saint-Gobain and Sto, who have embraced passive building solutions. One company struck me as especially interesting for the U.S. market: Compacfoam. They offer very simple thermally broken solutions using their compressed and structurally stable foam product. Those work for window installation, thermally broken point connections of curtain wall facades, point connections for balconies or porches attached back to the house structure as well as for the insulation of window frames. Those solutions could easily be implemented in the United States. All we need is the material.

Overall on the trade show floor, the innovations seemed to have leveled off some. In many cases the innovations presented were refinements of an already existing product. This is rather good news as it signals that passive in Europe has truly become mainstream. The smaller numbers of participants and exhibitors at the conference can be explained that way as well: other larger more general building conferences have absorbed the topic and are offering equally qualified information. Passive building is everywhere!

Some significant updates from the passive building modeling front:  This year, only one year after the last 2012 PHPP update came out, a new 2013 PHPP version has been published. Word is that the PHI significantly improved the cooling demand and latent load algorithms to be more appropriate for hot and humid climates. A new latent demand annual budget had already been included in the overall cooling demand certification criterion for 2012.

Newly unveiled to the European market (it was released earlier here in the States) at the conference: WUFI Passive developed by Fraunhofer IBP. The new passive modeling tool — that in addition to just a static calculation method also includes hourly dynamic simulation capability and hygrothermal assessment — was presented to the worldwide passive building community. Overall it was good to see that everybody in the field is working diligently on passive modeling tools that are accurate for all climates including the more challenging hot and humid ones.

Back to the PHPP update: be aware that if you still use the older versions of PHPP (2007 through 2012) for your passive designs, it is very likely that your results may not be as accurate as they could be. You should consider upgrading. If you are working in more complex and challenging climates (very cold climate zones starting at 8 as well as mixed humid, hot humid, hot and dry climate zones, plus  all zones with very high solar radiation) PHIUS very strongly recommends to use a dynamic model in addition to PHPP (or to use WUFI Passive which does both calculations — passive static verification and dynamic modeling).

Some caveats: The stated improvements/changes in the algorithms in PHPP 2013 are a great step – it marks an acknowledgement that cooling latent issues were indeed not properly addressed until now. But, these changes for cooling and latent have not yet been verified in the various North American climates. Moreover, with more built examples and data now available, the larger question is: How accurate can a limited static representation relying only on monthly climate data really be? It is very likely that it does not afford enough granularity to accurately predict very complex interactions of buildings with a multitude of climate factors.

For those more complex climates with heating, cooling, latent and solar climate factor combinations dynamic modeling appears to be quite a bit more accurate, allowing designers and consultants to limit the inherent risks in modeling: under or over-predicting performance as well as verifying that comfort conditions are assured throughout all rooms and spaces.

PHIUS is not alone with this recommendation of combining a dynamic model with a simplified static one for the best results. Belgium, the country that recently made the news with its decision to make Passive Standards code by 2015 for all new and retrofit construction projects, also requires all designers to back up the static passive house model with an additional dynamic model! Hence, the Belgian representatives of the Plate-forme Maison Passive I met with in Frankfurt were very interested and excited to learn about the advent of WUFI Passive.

Progress!

Kat

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PHIUS+ and DOE Challenge Home Partnership


On Monday, August 20, the U.S. Department of Energy (DOE) announced a new partnership between the DOE Challenge Home program and the Passive House Institute US to cooperate on the promotion of various levels of high-performance buildings on the path to zero net-energy.

This news is a huge development for the passive house community and for PHIUS. The endorsement of PHIUS+ passive house certification through the DOE instantly makes passive house the most energy efficient option for builders, designers and developers who want to achieve a zero energy building. This recognition will go a long way toward making passive house mainstream.

This took a lot of time and effort, and we owe thanks to Sam Rashkin, Chief Architect at the DOE, whose knowledge, vision and determination were critical to the effort. (Sam was the keynote at last year’s North American Passive House Conference.)

So, how does this partnership change current PHIUS+ passive house certification and what do consultants need to know?

In a nutshell: not much. A passive house already fulfills most of the Challenge Home requirements – certification essentially remains the same process with a few minor additions! Those additions are very good improvements, making the home even better. Indoor air quality requirements ask for low VOC materials and the water efficiency requirements establish a reasonable savings baseline, all good things.

The Challenge Home requires rigorous third-party, on-site verification, which already is part of PHIUS+. PHIUS+ certified RESNET Raters already use an advanced passive house checklist created specifically for passive houses. (This testing protocol is actually more rigorous than the one the Challenge Home is using.)

What Challenge Home brings to the table that PHIUS+  did not before is a more formalized exterior water management and flashing checklist. Having seen quite a few bad water management details during certification so far, we are happy to add a more formalized process to assure the long term durability of the house. QAQC is crucial to assure quality in execution, actual performance and peace of mind for the client we found.

The most noteworthy change will be the inexpensive requirement to install provisions for a future renewable system. Solar readiness must be built in so that getting to zero with a small affordable renewable system down the road is possible without any hassle, the right thing to do to show that we are walking the talk!

Beginning with all newly signed contracts starting September 1, 2012, PHIUS will provide a one stop-shopping option: Getting certified under PHIUS+ simultaneously gets the Challenge Home label and the Energy Star label, all which enhance market recognition and incentive opportunities. Best of all, it’s all for the same price as before.

Mark Miller, executive Director of the Passive House Alliance US is organizing a webinar  to discuss the partnership and to give everybody the opportunity to ask clarifying questions. And my conference presentation in Denver will be on this topic, more opportunity to ask for more detailed information.

Hope to see (hear and read) you at the webinar and in September at the leading passive house event of the year, the 7th Annual Passive House Conference in Denver!

Kat

 

The Anchoring Passive House Principle: Equal In – Equal Out

We are glad that this topic of local climate-specific refinement of the passive house standard has sparked such a lively debate and discussion. Clearly there is a lot of interest in the topic! That’s really good.

I’d like to take this opportunity to explain why our proposal to make passive house accommodate North American climate variations does not challenge the standard’s core principle.

We consider the passive house standard’s anchoring principle to be its commitment to comfort through near-perfect balancing of losses and gains. To date, meeting this goal has required minimizing peak load (the worst case scenario of heat loss on the coldest day of the year) to approximately 1 W/ft².  At this peak load only a very small back-up space conditioning source is needed to keep comfortable.

The original idea of this balancing act — and of the peak load target of 1 W/ ft²  — pre-dates the European passive house standard by more than 20 years. The peak load target was first introduced in the U.S. inaugural model energy code in 1975 (a code created as a result of the oil embargo in 1973). Today’s IECC commentary explains the principle very simply: If you have a room that is 100 ft² in area, and that room has a 100 watt light bulb in it, you are meeting your peak load requirement and don’t need a separate heating system.

Of course this is a very simplified way to describe the conceptual anchor of passive house, the light bulb being a placeholder for the sum of the internal energy sources matching the losses through the envelope, including ventilation losses. Equal in – equal out.

Now let me explain why we do not consider the 15kWh metric as either a magic number or an anchoring principle, but rather as a derivative of that peak load assumption. The 15 kWh/m²yr (or 4.75 kBTU/ft²yr) annual heat demand metric is used to identify the amount of heating energy consumed over the period of one year.

That 15kWh figure was derived for the German climate from the peak load target figure (1 W/ft².). It so happens that Darmstadt, Germany is one of the climate sweet spots where limiting heat loss to that 1 W/ft² (10 W/m²) threshold is possible with relatively reasonable and cost-effective amounts of insulation. Germany’s climate is called “moderately cold” for a reason. The delta T is not that great. Heating is the only climate issue that needs to be addressed. That makes the design process — relatively speaking — easy and clear-cut as there are no additional conditions, such as cooling needs or dehumidification, to consider.

We know the design recipe components necessary for building a European passive home envelope that keeps heat loss smaller or equal to our internal gains, or, in other words, meets the 1 W/ft² (10 W/m²) peak load criterion: we calculate the required amount of superinsulation; we use high quality windows, we assume airtightness at 0.6 ACH50…

In Central Europe, we reach the 1 W/ft² (10 W/m²) peak load target with an approximate insulation level of 14 inches of R-4 for a well-oriented, compact single family home. A practical and attainable scenario — in Darmstadt.

From the specs for that same house, we can calculate the total energy usage for heating over the period of one year based on the climate-specific heating degree days. For the Darmstadt climate, that annual heating demand calculates to approximately 15 kWh/m²yr or 4.75 kBTU/ft²yr. No rocket science. Simple energy balancing.

Therefore we do not consider the annual heating demand (15 kWh/m²yr ) as a fixed and given part of the “functional definition” of a passive house,. It is a consequence of designing to meet the peak load criterion of 1 W/ft² (10 W/m²) in the particular Central European climate.

The 15 kWh figure is a good median starting point for passive designs, as it is derived in a median type climate — median delta T, median length of time when heating is required — where the peak load balancing act is fulfilled almost perfectly. But this is only one specific climate with one specific combination of climate characteristics. This 15 kWh criterion will need to flex as the delta T and amounts of heating degree days change and the underlying principles are applied in different, more extreme climates that deviate significantly from the median base line climate of Central Europe.

Aside from heating, the existing standard is limited even further when we factor in additional North American climate issues such as cooling and dehumidification.

To reiterate:

  • We consider the passive house standard’s anchoring principle to be its commitment to comfort through near-perfect balancing of losses and gains.
  • To date, meeting that balance has meant minimizing peak loads to approximately 1 W/ft².  In Central Europe, that happens to pencil out to the 15kwh average consumption figure.

But, we will demonstrate in a future blog post that achieving that peak load goal (and therefore the 15kWh max threshold figure) is next to impossible in some climates, and definitely not practical. Because the peak load of  1 W/ft² doesn’t apply everywhere, neither can the 15kWh.

Other building science experts, Including Marc Rosenbaum, agree that the current standard has limitations, and offer their own ideas about addressing the issue. (Check out Marc’s proposal for New England.) The good news is that despite all these reasonable challenges to the notion of a single standard, the design principles still hold true, and the peak load target remains a useful tool as a benchmark — even if not an absolute in every single climate zone.

As we develop the specifics of our proposal, we look forward to discussion and debate among all interested and knowledgeable parties. Combined with the growing body of data we’ve accumulated from passive house projects that have been built around the continent, we believe we can introduce the flexibility that will make fundamental passive house principles mainstream practice.

In the meantime, look for more on lessons learned, climate complexity and how to possibly refine annual heating and cooling demands while maintaining the underlying physics principles in upcoming blog posts. Stay tuned!!

The standard: Less energy, less pollution, more comfort.

I’ve been on the road a lot lately but let me thank you again for your thoughtful contributions and the

Solar radiation exposure is one factor that differs dramatically between Germany and the US. (National Renewable Energy Laboratory, European Commission)

healthy debate sparked by my first blog post, “15kwh is Dead, Long Live 15kwh.” In the post I put forth PHIUS’ plans to modify the passive house standard to address the specific climate and market needs of the North American market. A quick summary of the changes and their value:

  • Modifications will be based on the first and only large-scale analysis of passive house buildings in the United States and Canada – the 100+ buildings certified/under review by PHIUS.
  • They will address the substantive and reasonable critiques (such as the small-home penalty) of leading building scientists in North America like John Straube, Marc Rosenbaum, and Martin Holladay.
  • They will safeguard the high quality for which passive house is known by acknowledging

    View Marc Rosenbaum's presentation on passive house in the United States from the 2011 North American Passive House Conference

    fundamental differences (e.g., building in high-humidity zones presents unique quality challenges).

  • Modifications will calibrate envelope improvements more precisely for each climate and will be more cost effective than the one-size-fits-all approach. They will improve cost effectiveness in colder climates while maintaining comfort and quality of the envelope. And they will actually tighten the standard in climates where there is opportunity for more stringent targets.

The post touched off a great deal of constructive discussion and supportive comments – many folks expressing support for an idea they believe was long overdue.

Understandably, the prospect of change also caused some angst. Recently, a petition was circulated asking folks to sign-on in support of maintaining a single numerical standard associated with the term passive house. I fully understand the response – years ago, I might have signed on myself. But since then, based on the collective experience of passive house consultants who have designed and constructed projects across the continent, it’s become clear that adaptation is critical.

It’s also become clear that we at PHIUS need to get better at explaining the rationale for the modifications that we’re proposing and how they will help propel the market forward while maintaining the core principles of passive house.

To that end, I’d like to respond to some of the concerns and ensuing discussion around the petition mentioned earlier.

Let’s start with a sentiment expressed in a Green Building Advisor article related to the petition topic:  It was expressed that the “beauty of the standard is its purity.”  Purity implies uniformity, and my intended point is that 15kwh is not a universal truth, and therefore not practical for all climate regions.  The rigor of passive house is universal.  In the US, 15kwh is rigorous and practical in the Pacific Northwest  but hat’s not the case in most of the other North American climate zones.

By the same token, in some areas of the United States – Southern California, for example – it’s technically and economically practical to do better than 15kwh.  And it’s worth reiterating: adjusting the standard will allow us to do away with the small-house penalty (that being that it’s actually easier to achieve 15kwh in a larger structure than a small one, thereby presenting an incentive to build larger).

As mentioned in the first blog post, other parts of the world have already concluded that 15kwh is not universal. This is really not a new development.

More important, is the suggestion that modifying the standard creates market confusion. Three points argue against this being a concern:

1. Passive house is not a brand. Passive house is a generic term for structures that require little or no actively generated energy for heating and cooling. Put another way: “Passive house” is the equivalent to “hybrid automobile.” Car manufacturers now make their versions with their brands.

2. Passive house applies to the principles and practices – which are universal – required to build passive structures. Many of them — superinsulation, airtightness, energy recovery ventilation, managing solar gain — originated in the United States and Canada. They don’t belong to anyone. They are not brands. And they are available to all designers and builders who want to learn to apply them. They remain intact and powerful regardless of any number.

3. As more competitors arrive in a growing market wishing to offer passive house products clear branding of different passive house products (different trainings, quality assurance protocols or standard variations) is important to avoid confusion in the market place. PHIUS has differentiated its product by creating the PHIUS+ program.

Market size is a bigger concern. Passive house has come a long, long way in the past several years. But the market is still tiny. The imperative is to grow the market. And it will not grow if we adhere to a standard that isn’t practical in large swaths of the continent.

By making the standard applicable across the continent, and teaching professionals how to make passive house work where they work, we can help passive house principles go mainstream here in North America. We can make passive house principle best practice. And that will achieve all of our ultimate goals: Less energy, less pollution, more comfort. All thanks to passive house.