Pioneering Leadership. Comprehensive Perspective.

High-performance, sustainable buildings don’t just happen by accident. They require careful planning and a global perspective to ensure projects are completed to the highest environmental, efficiency, quality, durability, and health standards available today.


Tadashi Shiga


Tadashi Shiga is the owner and creator of Evergreen Certified LLC. Growing up with deep roots in the Seattle real estate and development community, Tadashi has now been a real estate broker in the area for over 20 years. In 2007, he dove into learning about sustainability and energy efficiency for homes, shifting his focus and gaining a new passion. Tadashi then worked to become an Energy Star verifier and HERS Rater, and slowly began building a client base of developers and builders in the Seattle area looking to build green. Today Evergreen Certified has a client base of 150 builders and provides verifier and rater services for numerous programs including Built Green, PHIUS+, HERS, WaterSense, DOE Zero Energy Homes, NetZero and Energy Star.

Tadashi was the first PHIUS rater in Washington, and was involved with the first DOE Builder’s Challenge home in the state in 2010. Evergreen Certified won the Built Green Hammer Award in 2013, and has been the green verifier for the 2013 & 2015 DOE Housing Innovation Award Dwell Development projects. Tadashi has also been hard at work turning his own home on Vashon Island into a Net-Zero property. Tadashi leads a passionate team of green building professionals who help Seattle be a greener place.



Sean Conta

sean head shotWith a background in engineering, tech startups, and residential construction, Sean brings a strong set of technical skills to the Evergreen Certified team. Sean is a HERS rater, Built Green verifier, PHIUS+ rater, and NGBS verifier. As Field Operations Manager he is the point person for helping builders plan and achieve their sustainability goals. Evergreen Certified clients are likely to meet Sean on-site during construction or in the office for game-planning.  Sean has a passion for sustainability and construction. There’s nothing he likes more than “geeking out” on the latest green building equipment, techniques and wall assemblies. He joined the team after a stint as a bags-on residential remodel carpenter which gives him a valuable perspective from which to advise builders and developers.

When you are doing what you love, every day is a pleasure. Sean brings an easy-going attitude and sense of humor to all his interactions. As a father of two young children Sean does not have what is known as “spare time”. But if he did, you’d find him playing the drums, hitting the slopes, or working on his own 1916 Craftsman home.






Cybil Tribie

Having studied Environmental Science with an Engineering and Technology concentration, Cybil realized her passion for green buildings in the many classes she took. Her favorite was in fact ‘Environmentally Friendly Buildings’ where she learned much of what she is applying in to her work today. Beyond her knowledge of “green” practices, Cybil worked on the construction site for Habitat for Humanity where she gained some useful hands-on building experience. While working there, she learned the greater long-term value in building sustainably for everyone.

Her goal at Evergreen Certified is to make everything as easy as can be. Working from the ground up, Cybil can be found out on sites, holding builder meetings, and compiling final submittals. When not at work, Cybil likes to spend time watching movies, learning a new hobby, or returning home to Port-au-Prince Haiti to visit family and appreciate the warmth of constant sunshine!






Tracy Yamada

As our Office Administrator, Tracy handles all of Evergreen Certified’s proposals and financial interactions with our fantastic clients.

After having the opportunity through her husband’s work to have lived in many states and overseas, Tracy found a new love for sustainability. She is happy to have this opportunity to work with Tadashi and his team.

Tracy spends most of her time outside of work caring for her two children. If not at a pool watching swim meets or being the family taxi, you can find her at the gym, spending time with friends and enjoying the outdoor beauty of the Pacific Northwest.







Greta Tjeltveit

Greta first found her passion for sustainable building while doing a research paper on the work being done to rebuild New Orleans after Hurricane Katrina. Since then she’s continued to learn more about green design, residential construction, and cultural and historical preservation while studying architecture at the University of Washington. After obtaining her B.A. in Architectural Studies, she spent two years gaining construction experience at Habitat for Humanity.

Now as the resident young person in the office, Greta plans to kickstart Evergreen Certified’s social media presence, do site visits, blower doors, energy models, submittals, but most importantly, keep the team up to date with hip lingo.

Outside of work, you’ll find Greta on the soccer pitch, hitting the trails: running or hiking, listening to live music, or watching Seattle and Minnesota sports.

P.S., it’s pronounced “Chelt-vayt”