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Building Science

Is NIST Serious About Net-Zero-Energy Homes?

Their report cites the need for a scoring system, but inexplicably fails to mention the HERS Index

Image 1 of 3
The NIST Net-Zero-Energy Residential Test Facility will simulate the energy use patterns of a family of four to help refine guidelines for net-zero homes.
Image Credit: National Institute of Standards and Technology
The NIST Net-Zero-Energy Residential Test Facility will simulate the energy use patterns of a family of four to help refine guidelines for net-zero homes.
Image Credit: National Institute of Standards and Technology
This table from the Strategies to Achieve Net-Zero-Energy Homes report shows how they identified and prioritized items in the whole building design category.
Image Credit: National Institute of Standards and Technology
The HERS Index scale, which provides a good way to compare houses based on their modeled energy consumption. The NIST report oddly made no mention of this scoring system, even though they cited the need for one.
Image Credit: RESNET

The National Institute of Standards and Technology (NIST) still handles a lot of our basic numbers work, keeping lasers, hunks of metal, and atomic clocks that determine our standards of length, mass, and time. But it turns out they also have an interest in net-zero-energy (NZE) homes.

They’ve built and outfitted an amazing NZE research facility, and they also have convened meetings of experts to develop guidelines for NZE homes. But there’s something about their latest report I just don’t understand.

The photo at right is their recently completed Net-Zero-Energy Residential Test Facility (NZERTF), which is pretty darn cool. For its first year, it’s going to be operated as if a family of four were living in it so they can monitor just about every detail of its performance and get a lot of almost-real world data about NZE homes. You can check out this nice video about it to get a feel for what they’re doing.

Developing guidelines for NZE homes

In addition to their NZE research, NIST has also been hosting meetings of experts over the past few years to help gather what we know and figure out what we need to know yet about NZE buildings. Their most recent one was called Strategies to Achieve Net-Zero-Energy Homes, and in April they just released a report on the meeting. It’s called Strategies to Achieve Net-Zero-Energy Homes: A Framework for Future Guidelines Workshop Summary Report (pdf), and you can download it by clicking the linked title.

As they say in the introduction, the purpose of the report isn’t to tell you how to do it but rather “to aid in developing a set of future guidelines for the residential building community and homeowners as they design, construct, and operate NZE homes.” Some of the folks who were at this meeting are Sam Rashkin, formerly with Energy Star new homes program at EPA, now at US DOE; Dave Karmol of the International Code Council; Asa Foss with the U.S. Green Building Council; and Wes Davis of the Air Conditioning Contractors of America.

The document reviews where we’re at with regard to understanding how to do net-zero homes properly. The three main categories they focused their efforts on are:

  • Design challenges and tools
  • Technology and equipment
  • Homeowner and building industry needs and behavior.

Within each category, they identified the big issues and then prioritized them as high, medium, or low, as shown in the section on whole building design:

The report also gives “challenges and barriers” and “potential guidance elements” for each of the three main sections above and goes into some detail about the items discussed by the group.

Where is RESNET’s Home Energy Rating System?

One thing puzzled me about the report, though. On report page 9 (pdf page 19), they write, “A scoring system is needed for homes to enable consumers to compare energy, durability, indoor air quality, accessibility, and other factors relative to their needs during the purchase of newly constructed and existing homes.”

I agree, and I believe that RESNET’s Home Energy Rating System (HERS) has already made a good start toward this end with the HERS Index. I can certainly understand that a HERS rating currently doesn’t do everything they want, since they’re looking for much more than just energy performance. Not once on that page, however, do the authors even acknowledge that a HERS rating already does the biggest chunk – the energy performance.

They don’t even list RESNET in the “Existing Resources” section. How can the Carpet Research Institute merit inclusion here but not RESNET? That’s a bit baffling to me.

Let’s get going with net-zero-energy homes

Overall, this report is a good start at identifying the issues we need to work on. NZE homes, I think, have the potential to be more appealing than other green building or energy-efficiency programs because it’s not just giving homeowners a feel-good label. The Earth Advantage Institute provides a certification for NZE and NZE-ready homes, using the energy modeling software, REM/Rate, to determine whether a home passes.

Net zero energy gives homeowners a goal and can help shape their behavior. Buying an Energy Star home is a good thing, especially with Version 3 of the program, but homeowners could move in and think they’ve already arrived. With net zero, it’s as much about how the owners live in the house as how the house was designed and built.

Homeowners will need to watch their energy consumption and modify what they do if they want to actually achieve net zero. Ask Amy Musser and Matt Vande or Steve Larson. They’ll tell you how important monitoring and adjusting is when you want net-zero performance in a net-zero home.

The NIST folks still need to get a bit more realistic, though. In addition to ignoring RESNET, they also gave a medium priority to this: “Triple-pane windows with ratings of R-7 and above will be employed.” Really? In every climate? No matter how low the cost of photovoltaic modules goes? A lot of good people on working on their reports, so they should be able to sort these issues out.

Still, this report is a valuable contribution that can help further the NZE cause. The bulk of the report is really good and should lead to a good set of guidelines for ne-zero-energy homes, something that could help to push this concept along.

Allison Bailes of Decatur, Georgia, is a speaker, writer, energy consultant, RESNET-certified trainer, and the author of the Energy Vanguard Blog. You can follow him on Twitter at @EnergyVanguard.


  1. watercop | | #1

    Sometimes I really wonder about the Feds...
    I echo Alison's comments

    The first thing that struck me as odd was their intent to operate the home as if a family of 4 was in it....Why not just find a family of four, maybe the family of someone on assignment with NIST or a nearby agency and have them ACTUALLY operate the home as a family of 4?

    Why have we spent who knows how many hundreds of thousands (Millions?!?!) of scarce federal dollars on something everyone here at GBA already pretty well understands...a simple, three step process:

    1) Build a pretty good house (or a Passive House if you are really into it)
    2) Install fairly decent lights and appliances
    3a) Enjoy energy bills about 1/4 - 1/3 of typical production tract houses
    3b) If motivated and site permits, put enough PV on the roof to offset the greatly reduced energy used by steps 1&2 above.

    None of this is rocket science!

    I saw the 3 tank solar and heat pump water heater array...typical family of 4?!? my backside! about 12? What did that system cost??? $10k?. I love the guy in safety glasses taking down notes about who knows what never know when a water heater might reach out and try to blind you! Presumably they've instrumented this stuff to the point where guys filling out tables on clipboards are unnecessary...or not!

    I saw geothermal HVAC, or at least slinky tubes in horzontal trenches. That's cool, but what about Minisplits or a variable capacity central split heat pump?

    I saw showers, lights, laundry, kitchen. How will they truly simulate small children who leave lights on, teens that shower for 30 minutes, kids that leave refrigerator and exterior doors open, etc.

    Will they run the laundry machines empty or put actual dirty clothes in them? Same question about dishwasher.

    To sum up, this seems a Federal boondoggle with the result of wasting millions to demonstrate what any decent building scientist, home performance contractor, off-gridder, or passive house enthusiast already knows.

    Maybe the data and recommendations will actually add to our fund of building science and home energy performance knowledge, but color me skeptical.

  2. leighadickens | | #2

    not really right-sized
    it appears that this house is aiming to show you can do net-zero even if a house "typical in size to a house in the metro DC area", and is not particularly aiming to be right-sized. Well, how that works out will be interesting data, although I'd agree that I'd rather see results from a real family of four living in it, instead of "as if a family of four was living in it." Maybe that can be year 2?

  3. Expert Member
    CARL SEVILLE | | #3

    Interesting Priorities
    Looking at pages 5 & 6 in the report where they prioritize various ideas raised at the meeting has some funny goals:
    Quality is integral to the design is a Medium Priority
    Design and Construction are implemented collaboratively is a Low Priority
    Performance can be verified post-construction is a Low Priority
    Improved indoor air quality is a Low Priority
    Lack of sales structure and lack of renewable resources are Medium Priories

    I'm not sure what they were trying to accomplish with this list of priorities, but it sure seems to me that some of their priorities are a bit skewed from where they should be.

    FYI Resnet is referenced on P 24 as an existing resource

    Love their reference to Existing Resources - Lessons Learned from Similar Models on Page 35, where they include The Erie Canal, Transcontinental Railroad, and NASA.

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