A Climate Action Turning Point!

That's friend of PHIUS and visionary NYC architect Chris Benedict (l) with Katrin Klingenberg.

That’s friend of PHIUS and visionary NYC architect Chris Benedict (l) with Katrin Klingenberg.

On October 29th I was fortunate to attend the NYSERDA low carbon and zero energy Buildings of Excellence Awards at the Building Energy Exchange in New York City. What a terrific time for projects that are about to and that have employed PHIUS+ passive building standards as baseline to get to zero energy ready! I counted at least 10 PHIUS+ project teams in NYSERDA’s three categories, Early Design Stage, Substantial Completion and Completed, that were awarded up to 1 million dollars for their projects!The awards were announced on the 7th anniversary of super storm Sandy, not a coincidence, as a reminder for urgent climate action. Seven years later, NYC is leading by action and is putting itself firmly on the path of global leadership in building energy and resilience. Thank you to an amazingly dedicated NYSERDA team for making this happen!

The week before the event, I keynoted the Boston Passive House Massachusetts Symposium to talk about the evolution of the PHIUS+ certification suite for passive buildings, and why they provide such great value on the path to ZERO. Here as well, political action was taken to combat climate change: MassSave staff announced significant incentives for low carbon and zero energy buildings and significant additional incentives if project teams go for passive building certification for their hi-rise residential projects. Certification requests from Mass have increased manifold as a result. Massachusetts in not far behind NY State in political will, turns out.

And just a few weeks before the Boston event, it was gratifying to find that at the Getting to Zero Forum in Oakland, California, passive building was simply understood as the logical starting point on the path to ZERO, no questions asked. During one of the plenaries the ASHRAE speaker proudly introduced the new ASHRAE standards committee: 227p Passive Building Design Standard. That was great news and evidence that ASHRAE is moving on the topic.

During the lunch plenary on day one the National Renewable Energy Laboratory featured PHIUS board member Mary Rogero’s students presenting their Solar Decathlon winning PHIUS+ Source Zero energy school design. For the closing plenary, California’s Commissioner Andrew McAllister presented on his recently completed and only recently occupied zero energy passive house in Berkeley and the benefit of energy independence. He had electricity while PG&E had shut off power supply to prevent fires, a consequence of climate change, to most of Berkeley including the entire Berkeley Campus. He was followed by Greg Hale, from NYSERDA, who spoke about applying the Energiesprong passive plus zero energy retrofit approach that he is spearheading in NYS and other zero carbon measures taken by the city.

And while most of the building action seems to be happening on the East Coast, quietly behind the scenes advocates have been working hard to get passive building into codes all over the country. When PHIUS was first established our lofty mission was to make passive building code by 2020. As ambitious a goal that was then in 2007, we have made significant progress toward it, and have paved the path for national success. NY State has included passive building as an alternative compliance path into the next stretch code and Washington State is on a similar path. Massachusetts has included an alternative compliance path for passive buildings and verification tools (no double modeling required) and Washington, D.C. also has included an alternate compliance path for passive buildings in their about to be launched ZERO Energy Code.

Most significant of all those developments is the establishment of the ASHRAE 227p standards committee. If successful they’ll created a passive building design standard that takes the best pathways from all existing programs and develop an even better, easily adopted design standard globally. That committee has now started its so very important work. The ball is rolling! Stay tuned for more!

Exciting times, indeed!

 

 

 

 

WUFI® Passive V.3.2.0.1 validation using ANSI/ASHRAE Standard 140-2017

Good news: PHIUS has completed modeling to validate WUFI Passive according to ASHRAE 140. Read the full report here

ASHRAE 140 is a comprehensive Standard Method of Test (SMOT) for the evaluation of building energy analysis computer programs. The ASHRAE 140 report provides the information accrediting agencies or jurisdictions need for validation or acceptance of WUFI ® Passive for code and policy purposes. In short, the standard describes test buildings (cases) in significant detail in order to model the building and compare results versus other software. It contains a comprehensive description of test procedures, as well as predictions generated by WUFI Passive software evaluated against predictive benchmarks.

The table below provides a description of the test cases used for ASHRAE 140 Validation. 

Table 1

Annual Heating and Annual Cooling Load results were reported for most cases, except for L302-L324A which only analyzed heating. WUFI Passive results fell well into the suggested acceptance ranges in all test cases when following Class II Procedures of ASHRAE Standard 140.  Most results fell toward the center of the confidence range as shown in the graphs below.
AHL Results

ACL Results

Authors: Lisa White, Jasmine Garland

 

A mid-cycle tweak of PHIUS+ 2018

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Space conditioning targets have been adjusted to reflect a statistical ‘Inclusive Fit’ rather than ‘Best Fit.’

PHIUS officially launched the PHIUS+ 2018 Passive Building Standard just over a year ago at the 13th Annual North American Passive House Conference in Boston. The passive building market seems to approve: not only have we gotten a lot of positive feedback from CPHCs and other design professionals, but PHIUS+ Certifications continue to increase. The most notable upgrades from the PHIUS+ 2015 standard add nuance to the space conditioning targets, adjusting them for building size and occupant density – passive building professionals do seem to appreciate this.  Another notable upgrade provides tiered source-energy targets and methods to hit those targets, depending on project goals.

Through the end of September 2019, PHIUS certification staff had the discretion to grant an exception for one of the four main space conditioning target criteria, as outlined in PHIUS+ 2018 Passive Building Standard-Setting Documentation, page 6. This allowance gave teams with projects already in planning some assurance that their efforts would not be wasted if their designs could not be revised to meet the new targets.  If a project was severely constrained on meeting a target, a “mulligan” could be granted based on majority vote from the certification staff. This also allowed flexibility in case the targets didn’t pan out in the real world even for clean-sheet designs.

Read the Full, Detailed Tech Corner Article

This “3 out of 4 ain’t bad” provision has now come to an end, and we have learned a lot from the many projects that have gone through the process. These case studies have allowed us to complete a mid-cycle evaluation of the standard. Determining optimum performance targets is an iterative process, and gathering feedback for future improvements is part of it. Thank you to all the teams that have certified to PHIUS+ 2018 helping us to dial in these improvements.

Moving forward, space conditioning targets have been adjusted to reflect a slightly different statistical fit from the original space conditioning target-setting process — an ‘Inclusive Fit’ rather than ‘Best Fit’ line. These updates will not disqualify any previously submitted projects in the PHIUS+ 2018 Certification process, as they are more inclusive than before. One sample graph of this is shown for the Peak Heating Load.

The Space Conditioning Criteria Calculator has been updated.

The Space Conditioning Criteria Calculator has been updated.

The resulting updated targets will be:

Cooling Demand = Original Target + 2.81 kBTU/ft2yr 

Heating Load = Original Target + 0.77 BTU/ft2hr

Cooling Load = Original Target + 0.45 BTU/ft2hr

The PHIUS+ 2018 Space Conditioning Criteria Calculator v2 has been updated to reflect the updates. Note the ‘v2’ at the end of the naming convention. 

Note

  • Projects with a contract date before October 1, 2019 may utilize only one path, (1) Use the updated calculator ‘v2’ or (2) Meet 3 of 4 space conditioning targets as described above.
  • Projects with a contract date after October 1, 2019 may only use the updated v2 calculator.

More details on this, as well as the graphs supporting the statistical analysis can be found in this Tech Corner Article

 

Exhaust fans and make-up air

SONY DSC

PHIUS Certification Manager Lisa White weighs in on a common challenge for passive house designers.

When it comes to exhaust for the kitchen range/cook-top, either a re-circulation hood or direct exhaust hood is allowed in PHIUS certification, and among projects in certification, there has been no dominant approach — we see it both ways about equally. 

When projects use kitchen hoods that exhaust directly to the outside, it’s common practice to provide makeup air relief when the hood is in operation. This is because that additional exhaust airflow is separate from balanced ventilation system, the building is very air-tight, and without pressure relief, the exhaust airflow causes slight depressurization in the building.

PHIUS has been asked to clarify if makeup-air is required for projects when direct exhaust is utilized in the kitchen. The short answer is, it depends. The longer answer is below.

The ventilation balance  requirements for certification are outlined in the PHIUS+ Certification Guidebook v2.1 Section 3.5.3.3, and copied below:

Regardless of type, the ventilation system must meet one of the following requirements for balance:image-2

  1. Total measured supply and exhaust airflows are within 10% of each other. (Use the higher number as the basis of the percentage difference.)
  2. The total net pressurization or depressurization from the un-balanced ventilation system does not exceed 5 Pa. The net pressurization/ depressurization that the ventilation system imbalance causes on the building is determined using the multi-point air-tightness test results graph.

Intermittent exhaust airflow rates for kitchen exhaust hoods are generally much higher than a continuous exhaust airflow rates in the kitchen.  For example, a whole house may have a total of 150cfm continuous, balanced ventilation, and may have a 125cfm kitchen intermittent exhaust hood. With this combination, option 1 above would likely never pass.

PHIUS has established a method for determining compliance with option 2 during design. A stress test must be used to see if this intermittent ventilation system would cause more than 5 Pa of depressurization in the building. For a single unit building, the stress test is simply measuring the effect of turning on the range hood. If that airflow rate causes more than 5 Pa of depressurization in the building, there must be a provision for makeup air. For multi-unit buildings, an appropriate ‘stress test’ has now been defined that is both conservative and realistic.

Read the full Tech Corner Article here: https://www.phius.org/Tools-Resources/TechCorner/Makeup%20Air%20Requirements%20for%20Direct%20Kitchen%20Hood%20Exhaust%20.pdf

And try out the Intermittent Exhaust Allowance Calculator here: https://www.phius.org/PHIUS+2018/Kitchen%20Exhaust%20Calc%20v1.13/Kitchen%20Exhaust%20Calc%20v1.13.htm

 

Countering a policymaker’s concern regarding passive house

We recently heard from a PHIUS constituent who had these comments about an experience with a policy maker who was skeptical about passive building:

In recent discussions about building performance compliance options for our city’s Stretch/Green Code, a committee member raised a concern about a provision for passive house design in commercial projects. He thought that current modeling software isn’t reliable enough for reasonable accuracy and cited it as a “fatal flaw.”

Monitored energy use is tracking closely to WUFI Passive models.

Click on the image for a pdf report: Monitored energy use is tracking closely to WUFI Passive models!

Knowing that there are large and small commercial passive house projects being successfully built, I hope you can speak to his concern. The more specifically this can be addressed – the good and the bad – the better.  We are strong believers in passive house design but need to confidently understand how reliable the available technology is before adding it to our building codes.

Essentially, then, the question many policy makers have is this:

Is Passive House Certification too Risky for Code?

Short answer No.

PHIUS+ Certification is based on the same science, data, and energy programs that building codes are built on. However…

Our community is indeed successfully designing and certifying residential and commercial buildings to the PHIUS+ Passive House Standards.

We have two terrific resource sites for both applications and with great examples. Here are the links to them:

  • https://multifamily.phius.org/
  • https://commercial.phius.org/

WUFI Passive, the design/certification and energy modeling software, has proven to be accurate in predicting energy use. We have the largest pool of certified projects in North America and actual measured data is available for many of those projects.

Where we have measured data,we have found that on average we achieve modeled vs. measured results of +-7%, which is the best I have heard of in the energy modeling industry.

That said, there is much confusion out there regarding two passive house certifications. PHIUS Senior Scientist detailed the substantive differences between PHIUS+ and the European approach. In short, ours is a climate-specific passive building standard developed under a DOE grant for North America that has proven to produce very accurate predictions (here is a link to the NREL publication: https://www.nrel.gov/docs/fy15osti/64278.pdf).

The German Passivhaus Institute uses a different standard, not derived from North American climates but instead from only one central European climate (one set of standards for all climates in the world). They also use a different modeling tool, a spreadsheet called PHPP. They have to my knowledge very few projects certified to date in the commercial and large MF residential sector in North America and have not published any modeled vs. measured data.

We initially used their tool for our projects and found a significant difference in modeled vs. measured performance. Overheating in summer was also a problem. In our experience, the performance was off by 25-30% pretty consistently from what was predicted by PHPP. That’s why we switched to a different, more accurate methodology and modeling tool.

So, to the policy maker who raised the concern, I would agree that the PHPP and German standard do have a problem in North America. I do not expect that policy makers take my word for it, either. We encourage code and other officials to vet the standards and design tools carefully before including them. And to all of the PHIUS community who are fighting the good passive building fight, we will be happy to provide you data that proves the performance of the PHIUS+ standard and the WUFI-Passive modeling tool.

Kat