Why PHIUS+? Science, Climate, Energy Modeling

 

Why do you build to PHIUS Standards?

Asked at the 2017 North American Passive House Conference in Seattle, WA.

“As opposed to building standard code buildings?”
—Nichole Schuster, Ashley McGraw (Syracuse, NY)

“The question really is, how do we respond to climate change in the buildings that we build?”
—James Geppner, Big Yellow Cab (Cold Spring, NY)

Schuster: “I design to PHIUS+ standards because it’s an intensely rigorous energy efficiency standard.

Geppner: “And if we’re gonna respond, then, we need something that’s science-based and we need something that’s performance-based.

It doesn’t just have one component or another, but it actually performs to a certain level. And that that performance is measurable.”

“My passion is using the best technology and the best in building science to model energy use in buildings and to improve building efficiency.”
—Maren Longhurst, Rodell Design (Spokane, Washington)

Geppner: “It’s one way to achieve basically, a building that requires very little energy and does so and produces a high indoor quality.”

Schuster: “I think it provides greater levels of resiliency. I think it’s tailored to our specific climates that we get the maximum benefit out of it, and it can also help us achieve other standards and goals like the Living Building Challenge, Energy Petal, for example.”

Geppner: “Part of what makes it the best is that it uses what I think of, or what I call the dynamic energy model.

Longhurst: “PHIUS provides software Wi-Fi Passive and Wi-Fi Plus that really get deep into the details of a project.”

Geppner: “The information that goes into designing a building is information from that region. It’s weather data, it’s climate data, so that when you have a house, it’s not thoughtlessly constructed, it’s constructed to the temperature of that region, the moisture of that region.”

Longhurst: “And allow us to predict what a project will do and help us to design that project to be the most efficient, and the most comfortable, and the best quality building.

Geppner: “An option to get away from a construction method—which there’s basically no technology, it’s kind of a 400-year old process—to something that’s more like the thinking and the modeling that goes behind constructing something like an iPhone, or a high technology product, and it works.”

 

PHIUS+: The path to positive energy

Become a PHIUS+ Professional and be a leader in the industry

 

PHIUS Monitored Data Collection: Initial Results Are Encouraging!

– Jordan Frazin, PHIUS Certification Staff

INTRODUCTION

Passive building strategies have become increasingly common throughout the green building community and there is an ever-expanding network of Passive House Institute US (PHIUS) certified builders, CPHC®s, raters, and verifiers throughout the country. Thanks to these professionals, PHIUS has a catalog of over 250 certified and pre-certified projects and hundreds more that have been submitted.

Many of these certified projects have been fully occupied for months or even years, and we now have the opportunity to dive into monitored data collection and analysis.

By gathering actual performance data – in the form of utility bills – we can improve our modeling protocols, and refine the practices used by all parties involved in the certified project, including component manufacturers. We also hope to gain insight into the intricacies of climate specific design and its financial implications for the passive building owner.

With the support and guidance of the Industry Advisory Council, this past summer, we began this data collection and analysis process in earnest. (Thanks to the project teams who’ve already volunteered to participate!) We are always seeking additional utility data—if you are willing to share your project’s utility data with us, please send a message to certification@passivehouse.us to state your interest. We will reply with your next steps.

We’re excited to report that we’ve already processed some utility data and begun to analyze project performance with regard to predicted versus actual site energy use. Here’s a summary of the process, and preliminary findings:

PROCESS

The data analysis process began by gleaning the appropriate data from the project’s energy model and then by organizing it in spreadsheet format to account for all categories. This was broken into space conditioning, hot water, auxiliary energy, lighting, appliances, and miscellaneous loads. (see Figure 1 below).

Fig. 1: A portion of our monitored versus modeled site energy calculations.

Fig. 1: A portion of our monitored versus modeled site energy calculations.

Once we determined the estimated monthly energy use for the building from the certified energy model, we then compared these predictions with the actual utility data provided by the CPHC or project owner (see Figure 2 below).

Fig. 2: An example of some especially thorough, recently received utility data.

Fig. 2: An example of some especially thorough, recently received utility data.

Due to the nature of the utility data billing period (often not beginning on January 1st), it sometimes became necessary to cobble a year’s worth of data together using months from adjacent years. In the cases where this occurs below, it will be noted in the chart title.

RESULTS

Project 1 – Single family home

This project, a single-family home located in ASHRAE climate zone 4A, was certified under the PHIUS+ standard prior to the release of the PHIUS+ 2015 standard. It houses four occupants. The ‘modeled’ monthly estimates shown below follow PHIUS+ 2015 modeling protocols.

Fig. 3: Monthly site energy use for project 1, using 12-months of data from the end of 2015 and start of 2017. PHIUS modeling protocol estimated annual site energy use with 92.59% accuracy.

Fig. 3: Monthly site energy use for project 1, using 12-months of data from the end of 2015 and start of 2017. PHIUS modeling protocol estimated annual site energy use with 92.59% accuracy.

Fig. 4: Monthly site energy use for project 1, using 12-months of data from 2016. PHIUS modeling protocol estimated annual site energy use with 87.91% accuracy.

Fig. 4: Monthly site energy use for project 1, using 12-months of data from 2016. PHIUS modeling protocol estimated annual site energy use with 87.91% accuracy.

As seen above in figures 3 and 4, PHIUS modeling protocol slightly underestimated the actual site energy performance of this project. Specifically, it appears as though we have overestimated July loads in both cases, and slightly underestimated most other months. However, overall, the estimates still track the actual usage quite well month by month and are only off by ~10% on average. 

Project 2 – Single family home

This project, a single-family home located in ASHRAE climate zone 5, was certified under the PHIUS+ standard prior to the release of the PHIUS+ 2015 standard. It houses two occupants. The ‘modeled’ monthly estimates shown below follow PHIUS+ 2015 modeling protocols.

Fig. 5: Monthly site energy use for project 2, using the same 12-months of data from years 2015 and 2017 as above. PHIUS modeling protocol estimated annual site energy use with 96.28% accuracy.

Fig. 5: Monthly site energy use for project 2, using the same 12-months of data from years 2015 and 2017 as above. PHIUS modeling protocol estimated annual site energy use with 96.28% accuracy.

 

Fig. 6: Monthly site energy use for project 2, using 12-months of data from December of 2015 and January through November of 2016. PHIUS modeling protocol estimated annual site energy use with 98.30% accuracy.

Fig. 6: Monthly site energy use for project 2, using 12-months of data from December of 2015 and January through November of 2016. PHIUS modeling protocol estimated annual site energy use with 98.30% accuracy.

We were very pleased with the results of this case, as it was by far our most accurate. However, we were soon informed of the occupants’ varied heating set-point preference of 65°F as opposed to the 68°F set-point embedded within our protocol. So, out of curiosity, we analyzed another energy model with the heating set-point at 65°F. The results of this exploration are shown below.

 

Fig. 7: Monthly site energy use for project 2, with interior temperature set to 65°F. This figure shows 12-months of data from years 2015 and 2017. PHIUS modeling protocol estimated annual site energy use with 87.28% accuracy.

Fig. 7: Monthly site energy use for project 2, with interior temperature set to 65°F. This figure shows 12-months of data from years 2015 and 2017. PHIUS modeling protocol estimated annual site energy use with 87.28% accuracy.

Fig. 8: Monthly site energy use for project 2, with interior temperature set to 65°F. This figure shows 12-months of data from December of 2015 and January through November of 2016. PHIUS modeling protocol estimated annual site energy use with 89.31% accuracy.

Fig. 8: Monthly site energy use for project 2, with interior temperature set to 65°F. This figure shows 12-months of data from December of 2015 and January through November of 2016. PHIUS modeling protocol estimated annual site energy use with 89.31% accuracy.

Despite the project operating at a lower heating set-point, our models still predicted site energy use with ~ 88% accuracy, with especially close predictions during the non-heating months of the year. As expected, these results shifted due to a predicted lower space heating energy use during the winter.

Project 3 – Single family home

This project, a single-family home located in ASHRAE climate zone 4C, was certified under the PHIUS+ standard prior to the release of the PHIUS+ 2015 standard. It houses four occupants. The ‘modeled’ monthly estimates shown below follow PHIUS+ 2015 modeling protocols.

Fig. 9: Monthly site energy use for project 3, using 19 months of data from January 2016 through July 2017. PHIUS modeling protocol estimated annual site energy use with 131.68% accuracy.

Fig. 9: Monthly site energy use for project 3, using 19 months of data from January 2016 through July 2017. PHIUS modeling protocol estimated annual site energy use with 131.68% accuracy.

In the case of project three, PHIUS modeling protocol significantly overestimated site energy use during the non-heating period . Heating months, however, were estimated with greater accuracy. Of the three projects analyzed, this was the only project with energy consumption far lower than we predicted.

We were initially stumped by this comparison, until our suspicion of unique occupant behavior was verified during this past October’s North American Passive House Conference in Seattle, Washington. Upon seeing these results during a presentation, an audience member (and friend of the home’s occupants) confirmed the occupants have extremely energy-conscious living habits.

CONCLUSIONS

Based upon these comparisons, the PHIUS modeling protocol appears to predict annual site energy within roughly 10% – a promising statistic moving forward. In some cases though, unique occupant behavior impacts actual performance of passive house projects in ways we cannot predict.

By continuing to analyze monitored data, we hope to increase our total sample size to the point of discovering climate-specific trends. Additionally, we believe that increased availability of monitored performance data will become a useful technical and marketing resource for passive building professionals, and lead to improved practices in the coming months and years. And lastly, this data can validate the level of savings you can achieve through PHIUS+ certification and provide a foundation of assurance that incentive programs can rely on.

PHIUS+ 2018

— Lisa White, Graham Wright, PHIUS 

During NAPHC2017 in Seattle, PHIUS Senior Scientist Graham Wright provided a glance at PHIUS+ 2018 during a lunch input session. Wright highlighted updates to the standard and also touched on what will stay the same. Much of the content discussed is also summarized in this blog post: Getting to Zero Part II: PHIUS+ 2018. PHIUS Certification Staff fielded questions and encouraged audience input – overall feedback was supportive. The updated standard is currently under development by the PHIUS Technical Committee. There will be a public comment period, more details on that will be released soon.

We also announced that PHPP models will not be accepted for PHIUS+ 2018 projects. Following rationale in this blog post (Transitioning from PHIUS+ to PHIUS+ 2015 Passive Building Standard), WUFI Passive continues to see notable updates. The next update will include an improved shading algorithm for PHIUS+ 2018, among other improvements. The two modeling platforms have diverged and PHPP is no longer suitable for PHIUS+ Certifications. PHPP is still accepted for PHIUS+ 2015 projects. Accepted PHPP versions are: 06-02-10 IP-overlay of v2007 through PHPP v8.5.

The new program is scheduled to begin taking pilot projects in January 2018, and will be fully released mid-March 2018. There will be a 6-month transition period, from March through September 2018, where projects will be accepted for certification under PHIUS+ 2015 or PHIUS+ 2018. After September 15, 2018, no new projects can register under PHIUS+ 2015. In order to ‘lock-in’ a project under PHIUS+ 2015, both a contract and project payment must be in place before September 15, 2018.

PROJECTED TIMELINE *

January 2018: Accept pilot projects under PHIUS+ 2018
Mid-March 2018: Full release of PHIUS+ 2018
September 15, 2018: Projects no longer accepted under PHIUS+ 2015

*Please subscribe to the PHIUS Newsletter for updated release information as it becomes available