Meet HOMEnz: Winner of Phoenix’s Sustainable Home Design Competition – Pt. 1

Thanks to our GREEN designated realtor, Alison Hamlet, for giving us the initial lead for this story, as well as her pool of knowledge and resources which brought this story together quickly. For background, Alison is on the AZ Green Chamber of Commerce, where she first heard the presentation for HOMEnz last December.  

When Marlene Imirzian & Associates Architects won the City of Phoenix’s Sustainable Home Design Competition, her chief designer, Jay Atherton, hit upon a concept influential to the entire design process.

Their design was judged by a diverse nine-member panel, which included architects, green builders and city planners, based on a criteria of energy performance, sustainability, affordability, replicability, public rankings and overall creativity and beauty. The $100,000 prize, with parameters set by the City of Phoenix and the Arizona Chapter of the American Institute of Architects, went to the top creative minds who could present a cool, sustainable design at mid-level cost.

But, as it turns out, when Atherton began designing the home, the project later adopted as HOMEnz (“nz” stands for net zero), the creatively beautiful mandate focused his attention, rather than solely the sustainability angle.

Imirzian and her team plotted to build their design on a lengthwise N/S orientation, and it informed an earthy, Case-Study Home inspiration Atherton sought to sew into the design.

“As far as the sequence of how design reacts with the sun, I thought it be great to wake up with the sun on the east side,” Atherton said. “So, we put the kitchen and the common space, on the east side, where a lot of the glazing was placed.”

Like its Mid Century Modern forbearers, practicality informed the design: the floorplan doesn’t cramp the occupants and the glazing, similar to any MCM design, ensures light floods in which narrows the gap between interior and exterior.

“The idea of doing an extremely insulated exterior shell and yet providing this open, permeable floorplan that opens to the outside,” Imirzian said. “Achieving that beauty and the wonderful way we live in this region is the best aspect of the house.”

Yet, to win a competition called the “Sustainable Home Design Competition,” sponsored by the local municipality, you can’t get by on looks alone: it needs to be noticeably sustainable.

Some modern materials, like Structural Insulated Panels (SIP), framing boards sandwiched between insulation cores for walls, or fabric screens for the exposed glazing, eased energy efficiency decisions early on which benefitted the design process. Yet, the project prerequisites demanded 80% less energy use than what’s typically built in our climate; this significant bar, motivated a shift in the team’s aesthetic mindset. In the initial drawings by Atherton, 40% of the home contained glazing, which forced the team “to go back and become very targeted” on the placement and proportions of the insulation of the home.

This goal required the project to have specific technical know-how on board, so Imirzian and team tackled the problem with the assistance of the collective knowledge of engineers, contractors or various sustainable consultants.

For instance, HOMEnz’s base model scored a 30 HERS rating, notably low for a home, which calculates the efficiency of the shell of the house and the total energy use to operate the mechanics. (The average home built today receives about a 75 HERS rating, but the lower the number, the more sustainable the house.)

Stephen Mogowski of Desert Skies Consulting, provided clarity to HERS performance parameters and its intricacies which optimized their design’s performance, when their own knowledge of these standards was rudimentary for the advanced task. In equal measure, the critical input from Henderson Engineering was instrumental in their efforts: Imirzian credits the engineering team at Henderson, through their analysis of possible mechanical system & electrical loads solutions, for the ultimate success they had with their HERS score. Other knowledge that was practically indispensable was offered by Contractor Jim Furcini, of Furcini Construction, who evaluated the cost and numbers to make the project affordable to the masses, a critical project goal.

When they finally reduced their energy load consumed by powering the home beyond project guidelines, they got closer to off-the-grid energy, or net zero, goals. And this meant the overall efficiency of the exterior kept the energy inside, which in turn didn’t demand a powerful, costly mechanical unit to offset the heat gain.

Yet, in spite of the accomplishments bestowed upon them by the City of Phoenix, as well accolades elsewhere, Atherton’s mindset still doesn’t stress the sustainability angle but alternatively what achieving this goal allowed him to create as a designer.

“Part of the misnomer about sustainable, especially net zero, homes, is that you have to live like a hermit to keep that energy in,” Atherton said. “It is really important, especially in your home, that you know and are connected to what is going on outside, not by looking at your watch but by looking out your window.”

Stay tuned for Part II, when these flexible plans will be made available for free on the city’s website, and the first 10 consumers will receive building incentives, saving thousands in costs. The ultimate goal for these homes is to spur adoption on a massive scale to meet their 2050 Sustainability Goals, to their way to becoming a carbon-neutral, zero-waste city.