Guest Post: Ben Newell on Zero Energy Residential Optimization Software

This is Ben Newell from Equinox Built Environment Engineering ( writing a guest blog post about our ZEROs (Zero Energy Residential Optimization software) program now linked through the PHIUS Design Tools page. We are excited to offer this new design tool to the passive house community!

 ZEROs is an easy to use web-based energy prediction modeling program, but much more! Those experienced in designing and constructing super-performing buildings know that minimizing energy is not the sole factor in design decisions. Other considerations such as minimizing costs and maximizing health are just as important, if not more so. These design parameters are incorporated into the ZEROs model, giving you more control.

The goal of ZEROs was to develop a design tool that is very powerful and complex behind the computer screen, but with a simple interface that is easy to operate and very user friendly. We think we’ve accomplished that and plan to offer many tutorials that will help guide users in their own designs. Our centerpiece, Equinox House, was designed using ZEROs and the hundreds of thousands of data points we’ve collected since its completion validate the results. More about the design and construction of the net zero energy Equinox House can be found at

Equinox House, Urbana, IL

Modeling of both new and retrofit construction is possible. Main input parameters for the building envelope consist of the location, base house cost, wall, roof, and floor sizes, R values, and costs. The ground heat transfer is also included, an important factor dependent on the location. After defining the envelope, window parameters are entered for each side of the house consisting of area, U value, SHGC, and cost.

When the shell has been defined, characteristics of the building systems, energy, and comfort are selected. These relate to the efficiency of the conditioning systems, base load appliance energy, and the number of occupants, comfort set points, and fresh air ventilation. A solar module allows one to define a solar pv system to achieve net zero with the house design entered.

Once the parameters have been fully defined, running the model will produce a set of results which are broken down into five categories; costs, air quality, thermal loads, latent loads, and electric loads. One unique feature of ZEROs is its ability to predict air quality levels. This considers the use of ventilation and energy recovery equipment, including our soon to be released CERV (Conditioning Energy Recovery Ventilator). Another feature is breaking out the latent or moisture loads, which are extremely important in super houses, but often not handled in modeling software.

A validated energy model is important in designing a house, but as important is the validation of the constructed building’s performance. Blower door tests can point to construction flaws, but they don’t tell anything about the air quality and systems operation. In conjunction with ZEROs, our Black Box IAQ test ( records data related to Indoor Air Quality. This test assures that when habited, a building is providing a healthy environment for its inhabitants.

Follow the ZEROs link to try a fully functioning free version of the software. The subscription version is also available, which allows you to save different project cases and generate reports with the data as well as go into more depth with the parameters for windows and temperature and humidity set points. We hope you will find ZEROs to be useful and easy to use and in the end result in many more high performance, healthy, net zero energy residences across the country.

If it wasn’t for Rio… in honor of the 20th anniversary

In 1992, nearly every country in the world took part in what was hailed a “historic moment for humanity.”

The Rio Earth Summit in Brazil delivered a plan of action that would tackle greenhouse gases and climate change, stop species going extinct and save the forests. And if all that wasn’t enough, they committed to creating a “safe and just world” for all.

Amid the optimism fostered by the fall of communism, global leaders embraced the “revolutionary” new idea of sustainable development – economic progress in harmony with the natural world.

Ian Johnston,

That first Rio conference inspired passive house. Twenty years later, Rio is again the site of the Earth Summit. As a small gesture to help meet the big challenge that still lies ahead…

 we are starting on this day of the 20th anniversary of the first Rio our new PHIUS+ SOURCE NEUTRAL designation as special recognition to those PHIUS+ certified projects that go the extra mile to zero out (plus or minus) their source energy with an appropriately sized active photovoltaic system.

I am working on getting the Smith House upgraded for its 10th anniversary of the groundbreaking coming up in October of this year.

And to all of you who keep fighting the good fight on this front, thank you!


The Importance of Passive House Building Certification

Hi all–finally back in the office after more travel; NY, D.C., among others. Some exciting news coming, so stay tuned.

There is no substitute for on-site testing and quality assurance by trained pros. (That's John Semmelhack, who runs the PHIUS+ Rater Training program, during the inaugural rater class.)

Right now, though, I’d like to weigh in on a subject that is coming up more and more frequently as awareness of passive house grows: Quality assurance and project certification.

Project certification is a form of risk management. It is assurance that an extra set of experienced eyes catches serious mistakes with serious financial consequences.

PHIUS+, launched this year, was designed to emphasize, equally, a two step-process: design review and thorough onsite inspection by RESNET-certified raters.

Before PHIUS+, when we followed the European scheme, the onsite component required only HVAC commissioning and a blower door test. Five years and more than 200 project reviews in the U.S. and Canada later, we understand the value of established quality assurance protocols. Without them, a built project can vary substantially in performance from what was initially modeled.

When we find problems, they fall into two main categories.

  • User error and omissions in the modeling process.
  • Faulty installation and lower performance materials replacement.

Project certifiers can catch the first category by reviewing the model on their computers. But the second kind of error requires on-site inspections by experienced professionals who understand passive house design principles and have practical knowledge of construction details, materials, and technologies specific to a region and its climate. (FYI: If you’re RESNET rater and you want to learn to rate passive house buildings, the next two-day rater training is coming up.)

I know—as do all of you who have designed and built a passive building—that there is a learning curve to building passive house structures. When a project goes through certification, it’s similar to a writer getting an editor. And every writer needs an editor!

Design is one main component, but the best designs require quality workmanship.

One of our certifiers joked recently that we should tell first-timers to shoot for 3.75 kBTU/sqft yr. We have seen first-time PHPP energy models rise from the 3s to 6 or 7 after the review and corrections have been made. There are documented instances of even greater variances that we’ve seen.

All the more reason to submit early, before the “hole is in the ground,” so that corrections and design recommendations during the PHIUS+ design feedback process can still be implemented. It also helps assure clients who hire a new CPHC that another independent party is watching over the consultant’s shoulder and offering help and advice.

And make no mistake, things can go wrong, and there are consequences. For example, we have seen two projects that did not go through the certification process, but that we were able to review after construction. In both instances, built reality varied from the model so much that the builders had to retrofit a more serious mechanical system. Imagine clients reporting on the first winter day that the bedroom on the north side of their home is an “icebox” that cannot be heated. Your bottom line takes a hit, and so does the reputation of passive house.

The truth is, a lot can go wrong. But it doesn’t have to.  PHIUS+ onsite verification ensures how much wood really went into the wall, which insulation material (and R value) was actually installed, what windows were actually installed, etc. One problem we’ve seen, for example: installing a lower solar heat gain glass in a very cold climate in a project that heavily relies on solar gain to meet the energy balance in the model. That project can fall out of the certification range when discovered on site (even though it looked OK at pre-certification). This scenario has consequences on energy balance, comfort, and—cost—the mechanical system may no longer be up to the challenge.

Last year at Building Science Corporation’s summer camp, one participant sought me out to tell me that he felt passive houses don’t work. I asked him why. He replied that he had received a phone call from an owner of a passive house in the Northeast. (This project did not undergo certification). The house had become unlivable in the in-between seasons and this was why our building science specialist had been called in!

The architect had leaned very heavily on the southern glazing and didn’t account for the exterior sun shading for the two-story glazed façade. The building turned into an oven in March! The solution: retrofit of a mini-split. But the harm is done:  This building, claimed as passive house, due to the added cooling requirement is not an ultra low-energy building anymore and does not come near the performance promised to the homeowners. And, the story of a passive house FAIL was circulated in an environment of influential building scientists. I’d call that lose-lose.

PHIUS+ certification means design and performance have been verified.

In this instance, I was able to explain and he understood exactly where the serious mistakes were made. He also grasped that they could have been caught and remedied during certification review. I may not have converted him, but he kept an open mind.

Apart from risk and reputation management, putting a project through certification is a contribution to the passive house community’s collective knowledge. Lessons learned to get disseminated to great benefit—at future training classes, at conference, and online. But lessons are only learned by review.

I hope that you take on the challenge of building passive house structures—and that you make certification a part of that process. It’s valuable to all of us.