15kWh is dead. Long live 15kWh.

Hi Everybody:

Welcome to my brand new blog! I hope to keep you updated on the progress of Passive House and PHIUS, and to spark constructive discussion along the way.

On that note, I’d like to start this blog by addressing what we at PHIUS think will be the central issue for Passive House in 2012: fine-tuning the Passive House standard’s certification criteria, which were developed for the central European climate and market, to the unique climate and market needs of the United States and Canada.

Having evaluated five years of data from PHIUS’ portfolio — including more than 100 reviewed and/or certified projects of varied building types in the United States and Canada (thanks to the good work of the Passive House community) — we came to the conclusion that it’s time to:

  • Allow for a modification process to the rigid annual heating and cooling requirement of less or equal to 15 kWh/m2yr or 4.75 kBTU/ft2yr for the North American continent’s more extreme climates.
  • Define what has been missing all together so far – a stringent requirement for the third load which is the significant energy consumed in North America for dehumidification.

This idea that we need to adapt the standard to various regions has taken root around the world from domestic energy experts like Martin Holladay, Alex Wilson and Marc Rosenbaum to Passive House groups from other countries, like the Swedes. From our perspective, we do not feel that this adaptation guts the value of Passive House.  Instead, the goal is to introduce a new balancing act into the standard.

On the one hand, we need to let go of the illusion that there is a god-given magical number that can cost-effectively be adhered

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

to worldwide. (The notion behind “15 is dead.”) In North America, in some DOE designated climate zones (specifically, top 5 and up and bottom 3 and down), the cost of meeting the mark is problematic. The added expense required to hit 15 is not recoverable over the life of the building.

On the other, we need to maintain the value of having a single baseline. (“Long live 15.”) The first 100 projects or so have indeed validated this benchmark as an appropriate design starting point for excellence in high performance building in North American climates.  The baseline builds into the standard a necessary rigor and elegance that gives the brand its strength.

The PHIUS Proposal

PHIUS is proposing to the PHIUS Tech Committee — composed of industry and policy leaders from the United States and Canada — to leverage the PHIUS dataset of 100 buildings, and to solicit feedback from the consultant community to create a new protocol that will allow Passive House professionals to determine practical modifiers to the standard to address climate, small home and retrofit scenarios. This new protocol would be used to determine the acceptable modification ranges for:

  1. Additional peak load allowances (heat, cooling, latent) per climate other than the cool moderate reference climate.
  2. Annual space conditioning requirements (heating, cooling and dehumidification) that follow from acceptable higher peak loads per climate other than the cool moderate reference climate.
  3. Annual source energy requirements. Based on the new annual requirements per climate other than the cool moderate reference climate.
  4. Airtightness criteria that will have to be re-evaluated based on climate; hygrothermal criteria might have to be added as well.

By introducing this protocol into the standard process, we start with the baseline design of 15kWh for a climate dominant space conditioning need (might be heating or cooling or dehumidification). It is business as usual from here. If you meet the governing energy metric in a cost effective way you are done. Congratulations!

If you find yourself in a climate that is more extreme, you will need to benchmark the economic benefit expectations. Using the new protocol, the level of insulation can then be fine-tuned within a small range of above or below the energy metric of 15kWh without sacrificing the quality and comfort criteria. Tuning down the conservation level in return fine-tunes the annual energy requirement specific to each project without having to resort to prescriptive measures, possibly wasting savings potential.

In this manner a new Passive House balancing act is achieved – 15kWh remains the only fixed criteria, while deviations to both sides are allowable within clearly defined parameters.

We envision this to be a simple evaluation process to determine cost-effectiveness that will not add significantly to the consultant’s workload or complexity of the design tasks. The recently announced PHIUS+ certification program — that introduces a level of quality assurance into the Passive House standard — can also be used to assure that all building science and quality criteria are upheld regarding this new protocol.

From Movement to Mainstream

Addressing the issue of modifications is a pivotal moment for high performance building in North America! Its time has come because we now have the dataset necessary to make these adjustments. PHIUS Tech Committee evaluation of over 100 projects represents the first study of an unprecedented volume of data on implemented Passive Houses in North America.

It’s also a pivotal moment because we are proposing a departure from a single one-size fits all international standard. We welcome everybody who would like to contribute to this effort.

This proposed shift of course will not happen overnight. There is a lot of work to be done.  It will be a careful, collaborative process driven by the experience and data gathered from real-world experience. I’ll be providing updates here, and PHIUS will provide updates via its e-newsletter and Web site in the next several months.

This progress is very exciting to me! I have been waiting for this for a while. We are finally tackling the contradictions that we all have been struggling with and it seems we are about to solve them.  In the process, I look forward to your comments and input — I hope you’ll use the comments feature (just click on the little bubble below) to weigh in!

Katrin