Pedro Castro has a vision for contemporary, affordable, Earth-friendly housing: Modular mother-in-law homes, or formally known as Accessory Dwelling Units (ADUs).

“I have a passion for modular architecture,” said Castro, owner of Magellan Architects in downtown Redmond who held a Modular Accessory Dwelling Units Design Competition at his office last Friday. “It’s housing built in a factory and then shipped to the location.”

Castro said he hopes Redmond, which is slated for monumental growth — especially in the downtown neighborhood — uses modular ADUs to help satisfy the housing demand.

Redmond Mayor John Marchione commended Castro’s design competition and said he hopes it raises awareness “that accessory dwelling units can be an attractive choice of housing.”

“ADUs provide an affordable alternative to recent college graduates, small families, or retired family members,” Marchione said.

ADUs “are secondary to an existing home and – as of April 2007 (Ordinance 2331) – are allowed in all of Redmond’s residential zones. In most cases, ADUs are limited to 1,500 square feet; they may be attached to, or detached from, the existing home,” according to the City of Redmond Web site.

Modular ADUs are pre-fabricated and then transported to the site. The only thing built on-site is the foundation, Castro said. The electrical and plumbing is already done.

“You come with a crane and drop it into the foundation,” Castro said of modular ADUs. “What is beautiful about it, is that it is built in a controlled environment, there is no waste, everything is pre-programmed on the computer. It’s very green.”

Castro held a Modular ADU Design Competition last Friday at his downtown office, featuring designers at his company and other outside architects. Dirk McCulloch, Brianne Culley and Josh Peterson, architects at Magellan, along with Tito Almario of Bellevue-based MulvannyG2 Architecture and Guido Seoanes-Peria, an independent architect, participated in the contest, which Castro hopes will be an annual event.

McCulloch’s design was named the winner by the group of judges, made up of prominent architects, consultants and contractors in the community.

The purpose of the contest, held at Magellan’s office in downtown Redmond, was “to explore innovative ways to combine modular construction methods with environmentally conscious materials,” said Castro.

The downtown area is expected to grow rapidly and there could be as many as 2,000 new housing units by 2010.

While Marchione said he supports ADUs, he does not “see Redmond building a large number of ADUs. I see ADUs as a strategy to supplement our other efforts to provide affordable housing options.”

It’s an option Castro, his crew and design buddies all know and would love to implement in Redmond.