PHIUS Certified Data for Windows program online

Graham Wright, who heads up the PHIUS Certified Data for Windows program, joins us today to provide clarifications on some key features of the program. And to clear up some misinformation.

I get and see online a lot of questions about the PHIUS Certified Data for Windows program, and how it differs from PHI’s Euro-centric program. Apologies—it’s clear that we haven’t communicated the program as well as we should have—but we are catching up to ourselves.

I’m happy to report that we’ve got data and climate recommendations for a nice range of windows online here.

The table lists products, climate zone recommendations, full data certificates and supporting THERM files.

There are a lot more coming—and we’ll be converting this static table to an online database soon.

For manufacturers and suppliers, we invite you to download a detailed description of the certification process (with an application form), and the document is also available at the program overview page.

In the meantime, I hope to clear up misconceptions and concerns about the program:

I heard that the PHIUS Certified Data for Windows program doesn’t account for whole-window R-value. Is that correct?

In fact, the program does provide recommendations based on whole-window R-value, and all have the force of criteria as far as manufacturers are concerned. Also the program provides recommendations / criteria on solar heat gain coefficient.  (They vary by climate from about R-5 to R-9.)

Why doesn’t the program address surface temperature factor (“fRsi”)?

Eventually, it probably will – but on the list of important future program improvements for North America, it’s pretty far down the list, after data publication, NFRC harmonization, air-tightness-durability, and Canadian Energy Rating. That’s partly because fRsi isn’t pertinent to hot climates (and there’s a lot of hot climate zone in North America), and we decided to pay more attention to solar heat gain coefficient.

We cover the condensation / fRsi issue by providing the THERM files, which allow consultants to calculate it if they wish, and more precisely, with respect to the expected interior humidity conditions for their particular project and climate. (I made an ASHRAE 160 + ISO 13788 calculator for computing fRsi requirements climate- and project- specifically. We make it available during CPHC training, and if you email me at graham@passivehouse.us, I’ll be happy to send it to you.)

Moreover, both the fRsi criterion and the single-height bar on U-value (at about R-7) look to be legacies of the single-zone origin of PHI’s window program.

Setting that high bar at R-7 has certainly spurred innovation. But our multi-zone system does the same thing – people want to “level up” from zone 3 to 4 or from 4 to 5.  A single standard, when it comes to windows, fails to inform a shopper whether a window is appropriate for a passive house project because it’s overkill in some places and under kill in others.

It also hurts manufacturers—many of them mainstream producers of very affordable windows—who, right now, offer windows that will work well in mild climates. Designers, builders and clients should have those options.

Moreover, we find much to admire in the NFRC system and would like to get the best of both worlds. Funding for such harmonization work is being applied for.

Do we really need the PHIUS window program?

Absolutely.

PHIUS’ window program is moving toward a critical goal: producing data in the format that passive house consultants need, and that enables direct comparison to windows rated by other EN-based outfits like PHI or say, IFT Rosenheim. Both window industry representatives and passive designers have told us this is critical if we want to energize the market. To be sure, the programs’ fundamentals are aligned, but the presentation and recommendation level is different in a number of ways. For example, PHIUS’ program is more fussy about solar heat gain and zone granularity. PHI’s is more fussy about horizontal / vertical.

At PHIUS we believe that passive house principles apply universally, but a single criterion does not. From their Greenbuild presentation, it was clear to me that PHI recognizes the need for climate-specific recommendations for components, including windows.  But as I understand it their window certification is still pass/fail at one level. PHIUS has moved more quickly on this front. Going forward, if you hear “this is a passive house window” people should know to ask:  for what climate?  Be wary of claims about passive house windows that don’t show any numbers or label or certificate, it might just be loose talk.

Why such a long name? Why not just PHIUS Certified Window, for example

We settled on the name with care. The AAMA or NFRC would say, you don’t have a “window certification program” unless you address air / water / structural issues. So PHIUS is not certifying windows (and neither does PHI by such lights).

We’re certifying certain data about windows, namely thermal performance, modeled. Hence, “PHIUS Certified Data for Window Performance Program.”

We did not include the term “passive house” because while designed with passive house in mind, the data—even for windows that don’t receive recommendations for passive application—will be extremely useful for designers.

Reality Show: Monitored Passive House results from Salem, Oregon

All — thanks for all of your contributions and comments about fine-tuning the standard. It’s going to be an exciting process. Continuing that discussion, let’s look at a few really good examples of certified Passive Houses that were modeled for various North American climate zones, and for which we have good monitoring data. The graphic below makes clear that generally, the climates of North America and Central Europe are not directly comparable. One small region–running from the northwest U.S. Coast into Canada–matches the Central European conditions.

 

Therefore, we’ll look first at a certified project in Salem, Ore., and evaluate how accurately the PHPP modeled the actual monitored experience.

The Salem, Ore., home that's been monitored for a year.

Again — as stated in the inaugural blog post, the core principles behind the Passive House concept, some of which date back to the early 1970s — are not in question. Minimizing the peak loads to a point when balancing the ins and outs (losses and gains) produces  a building that nearly reaches equilibrium. Such a building needs very little active energy input — and this only a few months of the year — to maintain comfort.

If the space conditioning meets our 1 W/sqft peak heating load and 0.8 W/sq peak cooling load requirements, then we get the icing on the cake: For mechanicals, we can either use point sources throughout the space or integrate the space conditioning in the ventilation air. In the Northwest, with next to no cooling requirement and lots of passive cooling potential, integrating conditioning and ventilation could prove to be the most cost effective solution.

Let’s look at how one Passive House project played out in Salem, Ore. The 16th & Nebraska project (also known as the Rue-Evans House, named for its owners) was built by Blake Bilyeu and his father. Blake Bilyeu is a pioneer — he took one of the first PHIUS Certified Passive House Consultant training courses offered. And by 2010, he had completed the 16th & Nebraska project. It became one of the first projects certified by PHIUS.

By U.S. Department of Energy climate zone definitions, Salem is considered a marine climate, characterized by:

  • mean temperature of coldest month between 27-65 F
  • warmest month mean of less than 72 F
  • at least four months with mean temperatures over 50 F
  • dry season in summer (month with heaviest precipitation at least 3x of driest month)

Here’s the Salem climate data at a glance:

And data for Bonn, Germany.

The climates are very similar: Average temperatures in Salem are a little higher by 4.6 F in winter in Salem, summer highs are the same, and precipitation is generally higher in the Pacific Northwest. Both locations have limited solar availability.

The project’s PHPP data at a glance confirms that both Passive House criteria are met: the annual heating demand criterion with 4.02 kBTU/sqft yr as well as the peak heat load with 2.9 BTU/hr.sqft. There is no need for cooling.

The general specifications of the exterior envelope components are:

  • R-45 in the wall, the roof has R-96, the floor over crawl space has R-51.
  • The average window installed U-value is 0.226 BTU/hr.sqft.F with orientation specific SHGC of 0.23 for E-N-W orientations and 0.46 SHGC for the South

Note: The window figures are unadjusted NFRC values. Passive House window calculations will result in slightly adjusted values. The PHIUS Technical Committee is developing a method for converting values and/or a protocol to more accurately calculate the window values needed for PHPP. The Tech Committee will make it available for comment in an upcoming PHIUS e-Newsletter.  Many thanks to Graham Irwin, John Semmelhack and Graham Wright, who already have devoted a lot of hours to this project!

Energy consumption at the project was monitored for a full year. Over that period, the home was occupied by its new owners (a young couple and a dog, and eventually the couple’s newborn baby. The owners blogged about their early experience — check it out.)

A detailed monitoring report on the first year was prepared by the company Ecotope. (Many thanks to the Ecotope team that graciously gave PHIUS permission to make the information available to the Passive House community. PHIUS plans to share more monitored data from other projects soon—stay tuned.)

Download the full report here. From the executive summary:

The 16th and Nebraska Passive House project located in Salem, Oregon is an impressive example of an energy efficient home. The home is built to the stringent requirements of the Passive House (PH) program. The home’s energy use for the first year post-construction place it in the top tier of the most energy efficient single family homes in the Pacific Northwest. The first-year stats for the project are listed below:

  • First Year Total Annual Energy Use: 5,413 kWh/yr
  • Electric Utility Cost per Year: $700
  • Energy Savings estimate over Oregon Code: 9,064 kWh/yr
  • EUI (using gross sq ft of 1,885 sf): 9.8 kBtu/sf/yr2

The Salem Passive House home blows away today’s code homes, and nearly meets — right now — Ed Mazria’s Architecture 2030  Challenge for 80% reduction:

Back to the original questions: how do actual results compare to what was modeled in the PHPP, and what conclusions can be drawn from potential deviations of the measured results to the modeled results?

To start, some of the results are rather unexpected:

The actual first year’s energy use came in between what was predicted and what is allowed in the Passive House program, 5,413 kWh/yr. This results in a 63% energy use reduction over an electrically heated home built to the Oregon 2008 Code. This represents a savings of $750/yr in utility costs.

The DOE Building America Program aims for 70% in overall energy reduction. With 63%, this is below what one might have expected. If the modeled results had actually been met the building would have been saving 73% over the code home. Reading on:

This home represents the upper limits of conservation that can be controlled by the designers and builders; or what can be achieved by applying most of the energy efficiency measures currently available. Space heating and DHW represent 13% of the home’s total energy use. The remaining loads are plugs, appliances, lights, cooling, and energy recovery ventilator (ERV) fans. Since PH is a modeled certification program, there is no guarantee that a home modeled to meet the PH standard will actually perform to the PH standard once built. It is clear that maintaining the PH energy use levels is a function of occupant behavior and lifestyle choices. More research and development of tools for modeling plugs and appliances in the PHPP program should be made available to the PH community.

The report points out higher plug loads and attributes this to the American lifestyle. As we have compared electrical loads modeled in PHPP and actual consumption, we find a large discrepancy between what’s modeled and actual results throughout many North American projects which seems to confirm the author’s explanation.  

Conclusion: We need more accurate protocols for the American household. We need to identify realistic stringent savings recommendations and adjust the initial assumptions in the household electricity sheet accordingly. This measured result also points to the potentially higher importance of the source energy criterion rather than the focus on annual heating demand.

The measured space heating demand constitutes only 1/4 of what was actually predicted. Once the additional household consumption is taken into account, though, in the internal heat gains the results once again are pretty close to what PHPP predicted. The modeled kWh amount for space heat in the diagram is reflecting the assumed 3.2 COP of the heat pump; if provided through direct resistance  that would amount to 3.2 times 694 kWh,  equaling a little over 1800 kWh/yr. The discrepancy is roughly the additional kWh use for the DVR and server, which is direct electric internal heat gain (no bonus through COP). That explains the total higher energy consumption.

In short, the predicted space heat demand result is indeed very close to the modeled prediction. On the flip side though, there is talk about energy used for cooling in the report and the PHPP modeled 0 energy use for cooling. Additional household consumption can be used to replace heating needs in winter, in summer it adds to the energy used for cooling needs.

The report concludes:

This 16th & Nebraska Passive House home represents the leading edge of current energy conservation. Insulation has been maxed out, the envelope is extremely air tight, and the glazing percentage has been reduced to 15%. The solar water heating system is providing 69% of the hot water energy, the home uses highly efficient appliances, low lighting levels, and a very efficient ERV. The remaining loads are a product of the American lifestyle and are the hardest loads to control without major impacts to lifestyle.

For the Northwest, the Salem example indicates that the PHPP is, as expected, reasonably accurate in predicting the annual space conditioning. Assumptions for household and plug loads need to be revisited and entered as correctly as possible, but this is not a climate but rather a market issue.

Just as in Germany, the Salem project proves Passive House is a good basis for net zero. From the report:

This project is a great example of what is possible with the PH program and represents one path to achieving net zero energy use. A 6-7 kW PV array on the roof with the current 3 people living in the home would take this project to a net zero energy status.

That’s a sizable PV installation, but, just like in Germany, forgoing active energy in favor of conservation is more cost-effective.

So we’ve seen what happens when we apply Passive House in a climate very close to the European climate. To predict space conditioning it works very well. American life style and market, we have some work to do.

Applicability in regards to humidity, hygrothermal concerns and the impacts on airtightness recommendations for this climate will be addressed separately at a later time.

Next, we’ll venture into more extreme North American climates to evaluate that experience. Stay tuned for more!

Kat