Certified Passive House Consultant Training at MIT!

I’m happy — and proud — to announce we will offer our nine-day Certified Passive House

Consultant (CPHC) training at the Massachusetts Institute of Technology! Phase I runs May 29-June 2, Phase II runs June 18-21.

The MIT-hosted program is a byproduct of our ongoing efforts to meet the challenges that passive house designers face in North America. One critical challenge is the moisture performance of a superinsulated wall. The correct design and choice of materials are probably the  most difficult aspects of passive housing in North America, where humidity and cooling requirements are big issues in many regions.

To meet the challenge, we are working with the Fraunhofer Institute, a global energy research and consulting leader, to incorporate in our training an in-depth introduction to WUFI (WUFI is a hygrothermal modeling tool developed by Oak Ridge National Laboratory in partnership with Fraunhofer).

Fraunhofer has a relationship with MIT and helped facilitate MIT’s hosting of the upcoming training.

Historical Tidbit:

For those of you who know the full history of passive house, being at M.I.T. has special signifcance. William Shurcliff, whose pioneering work preceded and helped lay the foundation for passive house, worked at M.I.T. and Harvard for many years.

Other Training Updates for 2012

  • A beefed up segment on hygrothermal building science and an introduction to modeling using the ORNL/Fraunhofer WUFI tool. Students learn to design superinsulated wall structures – in all climate zones — that are free of moisture problems. Note: The General Services Administration now requires that a WUFI model is run on every GSA project!!
  • Expanded coverage of large multi-family projects and dormitories including reviews of ongoing and planned projects across the United States; plus, a look at the first finished passive house commercial applications including office buildings.
  • Specific mechanical solutions for mixed humid and hot humid climates
  • An introduction to the PHIUS+ certification program, which introduces a RESNET approved quality control/quality assurance component to project certification, and leads to an accurate HERS score – essential for earning energy-efficiency  financial incentives.
  • For 2012, the in-class exam is now computer-based. The online portion can now be taken on the last day of training – students get results immediately upon completion, along with solutions so students can learn from incorrect answers. The computer portion is followed by a take-home passive house design exercise.

Since the first class back in 2007, PHIUS has continually refined the curriculum to focus on North American challenges and solutions. Seven hundred professionals have gone through the training program since its start. More than 300 have taken the class and passed the exam have gone on to design high-quality, high-performance buildings – homes, office building, schools and community centers. A select few have taken the PHIUS Train-the-Trainer program and become PHIUS instructors.

Questions? Email: training@passivehouse.us

I hope we see you in Boston. Or New York, or Golden, Colo., or … check out the full schedule here.  And read the full training description.


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!!