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The best new building in Honolulu this year? I casually asked a UH architecture professor the question in conversation, which then veers off to other subjects.

Minutes later, the professor interrupts himself: “The best new building in Honolulu? Rainbow Drive-In on Kapahulu — its new solar roof structure.”

I’m instantly intrigued and resolve to look at it more closely.

The flat��roof, held 12 feet aloft on three posts, hovers over a row of picnic tables and a handful of parking stalls directly makai of the order window at the busy, much beloved plate-lunch purveyor. Completed in April, the structure without fussy disguise — no stucco, no chevron appliqué — increases shaded seating by a third and, with its 53-kilowatt solar system on top, reduces Rainbow’s HECO bill by about 50 percent.

The impressive posts are galvanized-steel, T-shaped “carry beams,” sunk 5 feet into the ground. Painted a fleshy beige, they support seven steel I-beam rafters, or perlings, also beige, laid lengthwise across the carry beams. Resting atop the perlings is a grid of black, dual-anodized aluminum racks that secure the roof’s 3-foot by 5-foot��photovoltaic panels.

“We never intended it to be structurally beautiful, but, you know … it’s functional, so it’s beautiful.” — Jim Gusukuma, Rainbow Drive-In

The shiny plastic undersides of the panels and their wiring are plain to see, if one can look up between shovels of macaroni salad. Fluorescent lighting fixtures run along undersides of the perlings. One of the shaded stalls is reserved for electric cars, with a Bosch plug-in recharger mounted on a post.

The only design flourish is the perlings themselves, which extend nakedly a few feet beyond the PV panels along the roof’s Kanaina Avenue frontage. This gestural abstraction of roof eaves recalls the extended overhangs on some of the iconic, mid-century-modernist Case Study houses of Los Angeles; yet overall, the structure fits into Kapahulu’s defiantly modest jumble-of-a-streetscape like one of those multi-purpose lanai/garages attached to so many homes around Oahu. Or like the pop-up-tents that appear at beach parks on any sunny weekend.

Three years ago, Rainbow Drive-In won a 25-year extension on its lease, which made the roof project financially feasible, according to Jim Gusukuma, senior vice president of the family-held company. Rather than redevelop the drive-in, built in 1961 by Seiju and Ayako Ifuku, their son-in-law Gusukuma went for small-bore improvements.

“No, we didn’t need to redevelop. People are familiar with this place,” Gusukuma tells me as we sit in a small back room off the kitchen.

“But you know, electricity bills in Hawaii are rising all the time,” he says. “I’m personally concerned about greenhouse gases, too much carbon dioxide in the air. I mean, I own an electric car. In fact, I own several electric cars, so it was a no-brainer for me that one of the main things I wanted to do was put in some sort of solar energy to be less dependent of fossil fuels.”

“We need to strip down and simplify where we can, like Rainbow did.” — UH Professor Martin Despang

Was there any local inspiration for the design? I ask him. “No, not really, he says. (In fact, there was no architect at all, just engineers.) “I think it was born out of necessity and opportunity. If we put in a double cantilever, we could have some covered parking as well as shaded space for a few more tables. In terms of placement, we just knew we didn’t want to block our signage.

“The (building) code said the roof had to be so high, and we didn’t want to make it too low because then certain vehicles might not fit under it.”

Gusukuma looked at at a few similar, if pre-fab, projects around the island, including a single-cantilever PV roof at Windward Honda in Kaneohe. He brought in Kamaaina Solar Solutions, an offshoot of the pest-control company, to engineer and construct the roof, which, according to the building code, had to withstand 150-mph winds.

The project took about a year and cost about $300,000, according to Gusukuma.

Matt Cosbie, the general manager of who joined us for the interview, says that what Rainbow wanted wasn’t an out-of-box system. “We really had to go out and find the resources,” he says.

The project was delayed twice, according to Cosbie, because of HECO’s slowdown in issuing solar permits during the ongoing huhu over burgeoning solar-power generation by its customers and the impacts that is having on the utility’s net-metering capacity.

The delays actually resulted in Kamaaina going with a better, 305-watt solar module from a California start-up called Silevo, rather than the 285-watt module it had been considering from Korea-based giant LG. According to Cosbie, the Silevo modules, in addition to a 20-watt increase in generated power, have a better temperature coefficient; that is, lower heat generation in the module itself that positively impacts wattage output.

“Really!” Gusukuma interjects. “So, sun is good, but heat is not good? I didn’t know that.”

“Exactly,” Cosbie says, explaining that a nice sunny day in a Minnesota winter makes for better efficiency in solar panels — as do those intermittent, trade-wind rain sprinkles on otherwise sunny days that can actually cool off the panels and make them more efficient.

“So, that’s why my mileage went down on my (BMW) i3 this summer when it was so damn hot,” Gusukuma says.

The project was delayed twice because of HECO’s slowdown in issuing solar permits during the ongoing huhu over burgeoning solar-power generation by its customers.

I ask Gusukuma if he’s figured out at what point, after the costs of the project, tax credits, depreciation, etc., Rainbow’s roof will begin producing free electricity. About five years, he tells me.

“It kills two birds with one stone,” says cheerful Rainbow Drive-In employee Maria Borges of the roof, referring to the shading and electricity generation. “It’s really nice,” she says, gazing out from her station in Rainbow’s logo shop to the lunchtime customers chowing down under the new roof.�� The shop counter and displays occupy a little vestibule that’s actually one half of a shipping container; the other half is a few feet away and brimming with T-shirts ($20).

“I think the roof is beautifully designed,” Gusukuma says. “We never intended it to be structurally beautiful, but, you know … it’s functional, so it’s beautiful. We didn’t lose any parking!

“You know, [the roof] gives it kind of an old drive-in look, doesn’t it? Kind of a retro look, like the A&Ws and stuff like that on the mainland, with those roofs you park under. Of course, they do it because of snow and sleet.”

I ask him if it’s local style.

“Um, I don’t know that it’s local style — I mean, it fits with the drive-in concept, but yeah, maybe it’s local style in the sense that, you know, locals typically sit in their garages and eat!” He laughs heartily.

As for the UH professor, he is Martin Despang, who does double-duty as a practicing architect in his native Germany. A man of many words and ideas, Despang is passionate about Honolulu’s built appropriateness and its many inappropriatenesses,�� particularly among newer buildings, where we should know better.

Ever the optimist, he champions the “easy-breezy” vernacular style of Hawaii buildings and celebrates the primacy of indigenous Hawaiian forms��—��buildings as lanai, as simple shade and rain shelters. He calls it “roof architecture,” versus the invasive “wall architecture” born of chillier climes than ours.

Despang has shared his sustainable, cutting-edge ideas and architectural schemes with Kamehameha Schools, the Department of Hawaiian Home Lands, and various developers, while his students have dreamed up some marvelous schemes of their own.��

“Indigenous peoples alway did it right because they never did any more or less than was necessary,” Despang says. “We need to strip down and simplify where we can, like Rainbow did.”