PHIUS vs PHI – Lessons learned webinar recap

Katrin Klingenberg, PHIUS Executive Director

#PHIUS
www.phius.org

Thanks to all of you who took the time to join us for last week’s webinar on the differences between the PHIUS and PHI passive house and building standards. Due to popular demand (we sold out within 3 hours of the original offering) we had to get a bigger “boat” and were eventually able to get everyone seated!

Clearly, there is a lot of interest in the topic.

Two passive building design/construction standards are available in the North American market: The PHIUS+2015 Passive building Standard certified through the Passive House Institute US and the Passivhaus Standard certified through the German Passivhaus Institute.

We presented the webinar in response to growing confusion about the differences between standards and questions about how the programs compare to commonly used energy standards such as ASHRAE 90.1. Other common questions: Are they simply “two flavors of the same thing” or are there more fundamental differences between programs? Which program is more commonly used in North America’s widely varying climates and why?

As we all make progress in mainstreaming passive building to significantly reduce carbon globally, one lesson has become clear: details matter! Different standards and modeling protocols offer significantly different guidance to designers seeking cost- optimized, high-performance buildings in their region.

The European standard and its design parameters for energy comprise one target for heating and cooling to attain an optimized design solution in all climates and cost structures worldwide. The PHIUS+ tailors and optimizes energy targets for both climate and cost, and does so for every individual location. The updated 2018 version becomes even more granular by taking occupancy and building typology into account.

Two very different approaches.

If you missed the live webinar, you can still learn more about the differences and modeling protocols: A recording of the webinar is now online!

Some of the questions that were asked during the webinar and could not be answered are posted below and if you have any other questions please send us an e-mail at info@passivehouse.us.

Thanks again to all of you who attended!

Kat

A selection of Questions posed during the webinar event, that could not be addressed live due to time constraints:

When will PHIUS+2018 come into effect? How long can we continue to use 2015 for projects in development?

PHIUS+2018 will be launched at the Annual conference this September in Boston. Teams can still use PHIUS+2015 until March of 2019.

What can we carry forward as a message from PHIUS & you to building code legislators?

We have put a lot of thought into making PHIUS+ a good standard for how much the building sector contributes to climate goals and/or the renewable energy transition, while also protecting occupant health and comfort. We have given it features to make it suitable for policymakers to incentivize. We can do feasibility studies for specific model buildings in specific climates to give officials a better feel for what PHIUS+ requires and delivers.

It is my experience that PHIUS at this time does not accept published efficiencies of ERV’s, and therefore the derated efficiency of ERV’s are not compatible with PHIUS certification requirements.

We accept 3rd-party ratings from AHRI, HVI, and PHI as well as our own product program – only unverified manufacturer data is derated. For building project certification there is not a hard requirement on recovery efficiency for the ventilation, but yes, in some climates it will be hard to meet the other performance criteria without a good H/ERV.

Can you expand on the adaptation aspects of passive house for the changes which are observed and expected in climate?

Right now, our certification is based on TMY3 climate data, and will update when newer data becomes available. Although predictive future TMY climate data sets exist, these are not used for certification. Even so, the performance upgrades required to meet our criteria should provide resilience benefit against weather extremes and utility outages. Resilience and adaptation to changing climate can be evaluated in a different way, more focused than modeling a typical year for predicted energy performance. We are working on a form of resilience assessment for that purpose.

Followup comment by another attendee: I took the climate question to mean: if standard is zone-variable, can we on top of that adapt to how existing zones are shifting to becoming one zone warmer. 

We are working on calculations that would generate climate data taking possible changes into account.

Wasn’t PHI’s cost-optimization based on integrating ventilation into the heating ducts and not cost of PV?

The idea was to improve/invest in the envelope to a point so that a typical heating system, and the cost associated with it, could be eliminated. The now minimized heating system could be integrated in the ventilation supply air stream using the same fan and ductwork for delivery. In Germany, eliminating the heating system supposedly made up for the additional cost to improve the envelope. In the U.S., because ducts and furnaces are relatively cheap, that strategy does not net much if any savings after one adds the HRV. PHI did not include cost of PV at the time because it was cost prohibitive. In the U.S. today PV is no longer cost prohibitive and at some point becomes competitive with insulation. Yes, the point was that in the U.S., because ducts and furnaces are relatively cheap, said integration doesn’t net much if any savings after you add the HRV.

Has E-Quest been calibrated against measured building performance for a large sample size of buildings?

I would assume so, it is widely used for code compliance modeling.

Is there a bigger sample size of monitored data on single family homes like the one in Oregon?

Yes

Is there any measured data to correlate with the modeling comparisons on Slide 27?

The NYSERDA study was on model buildings not actual, so we can’t get a direct comparison in that case.

In the future will there be more resolution than the ASHRAE climate zones for space conditioning criteria?

In all likelihood yes.

Going back to the financial graph, would you say that solar thermal is pretty incompatible with PHIUS or could it still be useful in certain climate areas?

At this point it appears not to be very cost-effective, but it could still have a resilience benefit in some climates. System complexity works against resilience, and climates that require freeze-protection tend to have more complicated systems.