Who We Are.
Founded in 2009, Ramirez, Johnson, and Associates provides engineering solutions with a customized approach that delivers the best value for every project. As a small firm, we can give each client and project the personal attention deserved. Licensed in Colorado and beyond, our engineers, commissioning agents, and designers are ready to take on projects ranging from $1,000 to $100,000,000, including commercial spaces, healthcare facilities, educational facilities, multi-family and high-end custom residential projects. RJA is M/WBE, DBE, SBE, EBE Certified.
Our Partners.
Darin Ramirez, PE
Founding Partner
As a founding principal of RJA, Darin provides experience attained since 2004 in the design, construction, and consulting industry. He is involved in all aspects of the firm’s daily operations. As designer, Darin’s passions include collaborating with owners and users to truly understand their needs, and providing design solutions that are efficient and appropriate for each clients. Off the clock, Darin can usually be found chasing his kids, climbing, and skiing in the Rocky Mountains.
Education:
Bachelor of Science, Mechanical Engineering, University of Florida
Affiliations and Registrations:
Professional Engineer: CO, KS, MD, MN, NC, NV, NJ, NM, OH, OK, OR, PA, SC, TN, TX, WA, WY, MT, and UT
Certified Geoexchange Designer
LEED AP
Eric Johnson, CxA
Founding Partner
Eric’s passion for buildings and sustainable design directs the work of the firm and his construction and contracting background provides a practical perspective on each project. With two decades of experience, Eric is involved in either a design or commissioning role on every project and excels at leading talented engineers and designers towards solutions that are in the best interest of the client and the project. As a strong community supporter, Eric’s volunteerism through Junior Achievement helps to provide a positive and lasting impact on young people’s economic and entrepreneurship skills, career choices, and success. During his free time, Eric enjoys skiing, hiking, golfing, and spending time with his family.
Education:
Bachelor of Science, Architectural Engineering, University of Colorado
Affiliations and Registrations:
LEED AP
Certified Commissioning Authority, CxA
Our Engineers.
Paul Plewczynski
Electrical
As an electrical designer, Paul has amassed engineering experience in the Denver area since 2007. His background includes roles on the owners’ team as well as on the consulting side of the industry. Paul is responsible for spearheading RJA’s Revit/BIM collaboration with our clients, and he specializes in new and existing projects that require creative power distribution design.
Paul enjoys hiking, backpacking, and mountain biking with his wife and three kids.
Education:
Bachelor of Science, Electrical Engineering Technology, MSU Denver
Associates Degree, Computer Aided Drafting, ITT Technical Institute
Affiliations and Registrations:
ICT Design Fundamentals
Scott Zimmerman, PE
Mechanical Engineer
Scott is a mechanical engineer with experience in the commercial and industrial sectors. Since 2010, his varied project background includes telescope observatories, college sports facilities, mineral processing plants, commercial kitchens, and breweries/distilleries. Scott is well versed in the BIM/VDC design process and is a proponent of 3D modeling software.
In his free time, Scott enjoys fourwheeling and exploring Colorado’s backcountry.
Education:
Bachelor of Science, Mechanical Engineering, University of Arizona
Affiliations and Registrations:
Professional Engineer: AZ, CA, CO, IA, ID, and UT
Member ASHRAE, former Chapter President
LEED Green Associate
Judah Katz, CxA
Mechanical
Judah is a talented and detail-oriented individual with over a decade of mechanical and plumbing design experience in the residential, commercial, and light industrial sectors. His project experiences are comprised of a diverse group of industries including educational facilities, restaurants/breweries/bars, retail spaces, institutional housing, and higher education. Technically, Judah is adept in the use of multiple energy modeling, BIM, and design softwares. Judah became a certified Commissioning Agent in 2024. Family, music, and finding ways to enjoy the sun are his choice priorities when not in the office.
Education:
Bachelor of Science, Mechanical Engineering, University of Alabama
Affiliations and Registrations:
Certified Commissioning Authority, CxA
Member ASHRAE
Chris Wood
Mechanical
Chris began in 2012 as a mechanical and plumbing designer acquiring experience in multi-family and light commercial construction. He has engineered and managed projects from 350-unit multifamily buildings to small office tenant finishes. Chris moved to Denver from Western NY in 2009 after graduating from Alfred State College. In his off time Chris enjoys biking, hiking, and spending time with his dog.
Education:
Bachelor of Science, Mechanical Engineering Technology, Alfred State College
Theresa Gray, PE
Electrical Engineer
Working in the electrical and lighting design industry since 2001, Theresa’s passion for lighting design and efficient power systems has helped shape countless projects. Theresa is licensed professional engineer and active member of the Illuminating Engineering Society of North America.
Education:
Bachelor of Science, Architectural Engineering, University of Colorado, Boulder
Affiliations and Registrations:
Professional Engineer: CO, AZ, MD, WY, WA, UT, TX, MN
IES
LEED AP
Andy Achtermann, PE
Mechanical Engineer
Andy has worked as a mechanical engineer since he graduated in 2012. He specializes in a variety of residential, commercial, and industrial building system types including but not limited to: restaurants/bars, hotels, low to high-rise multi-family, schools, offices, and process design (steam and grow facilities).
In his free time, Andy enjoys traveling, golfing, baking, and brewing beer.
Education:
Bachelor of Science, Architectural Engineering, University of Colorado, Boulder
Affiliations and Registrations:
Professional Engineer: CO, AR, and TX
Member ASHRAE
Ryan Liberman, EIT
Mechanical
Ryan joined RJA as a mechanical designer in 2020. His background includes a degree in Engineering Physics from Tulane University and his technical background includes designing HVAC systems in the New Orleans area. His hobbies include snowboarding, Ultimate Frisbee, and Fortnite.
Education:
Bachelor of Science, Engineering Physics, Tulane University
Nora Raine, EIT
Mechanical
Education:
Bachelor of Science, Mechanical Engineer, Iowa State University
Charlie Shae
Business Manager
Education:
Bachelor of Science, Biotechnology, University of Nebraska at Omaha
Master’s of Architecture, University of Colorado Denver
Affiliations and Registrations:
LEED Green Associate
Henry Furuta, PE
Mechanical
Henry entered the MEP industry in 2018. He has designed mechanical and plumbing systems for a wide variety of projects across the country from sports stadiums to office tenant improvements, and enjoys 3D modeling. In his free time he spends his time playing Ultimate Frisbee, traveling, and flying.
Education:
Bachelor of Science, Mechanical Engineering, University of Texas at Austin
Affiliations and Registrations:
Professional Engineer: CO
Derek Wetch
Mechanical
Derek is a mechanical and plumbing designer with experience in the multi-family and restaurant sectors. He has a unique background as a field engineer, having served as both a Project Engineer and a VDC Engineer in Montana. Derek has proficiency with utilizing Revit and Navisworks through all stages of the design and construction process.
Derek earned his master’s degree in Mechanical Engineering at the University of Colorado Boulder in 2023. When not at work and school, his hobbies include backpacking, fly-fishing and backcountry skiing. An Arvada native, Derek is excited to use his skillset to build Colorado responsibly.
Education:
Bachelor of Science, Mechanical Engineering, Montana State University Bozeman
Masters of Science, Mechanical Engineering, University of Colorado Boulder (In progress)
Shelly Achtermann
Electrical
Shelly has worked as an electrical designer since 2018. She enjoys designing energy efficient power and lighting systems for commercial, industrial, and residential projects. Her project background includes multi-family, offices, restaurants/bars, schools, warehouses, and retail spaces. In her free time she likes to hike, garden, play with her dogs, and tend to her chickens.
Education:
Bachelor of Science, Biological Sciences, Colorado State University
Kevin Sweeney, PE
Mechanical Engineer
Kevin is a licensed Mechanical Engineer who has been working in MEP design since graduating from North Carolina State University in 2015. After relocating to Denver in 2022, Kevin joined RJA bringing with him a wide variety of project experience including multi-family buildings, restaurants, offices and historic building alterations. Outside of the office, Kevin enjoys exploring new places on his bike.
Education:
Bachelor of Science, Mechanical Engineering, North Carolina State University
Affiliations and Registrations:
Professional Engineer: CO & NC
Huseyin Martin Yildiran
Mechanical
Martin is a mechanical and plumbing designer who takes pride in helping owners and contractors identify design efficiencies in their project. His knowledge of different mechanical systems is integral to RJA’s ongoing priority of assisting clients’ understanding and achievement of the updated Energize Denver requirements. Martin also has unique experience with California Title 24 energy standards. In his free time, Martin enjoys playing and watching basketball and soccer, playing video games, and swimming.
Education:
Bachelor of Science, Mechanical Engineering, University of Sakarya, Turkey
Alex McPheeters
Electrical
Alex has worked as an electrical designer since graduating from Colorado State University in 2021. He has experience in industrial power engineering and a background in Mechanical Engineering. Alex moved to Colorado from Phoenix, Arizona for school, and in his free time he enjoys golfing, racing, and weightlifting.
Education:
Bachelor of Science, Mechanical Engineering, Colorado State University
Minor, Biomedical Engineering, Colorado State University
Sammi Reeves
Electrical
Working as an electrical designer since 2017, Sammi relocated to Denver in 2023. Her background includes electrical design, specializing in large-scale commercial and retail spaces. Sammi leads the electrical team in Revit/BIM application, with a strong emphasis in multi-discipline coordination and collaboration. In her free time, she enjoys hiking, reading, and spending time with her dog.
Meryem Canoz
Electrical
Education:
Bachelor of Science, Electrical & Electronics Engineering, University of Gaziantep, Turkey
Ava Lawrence
Mechanical
Ava has worked as a mechanical engineer since she graduated from The University of Vermont in 2020. She has experience designing mechanical and plumbing systems for residential, commercial and office spaces. She relocated to Denver shortly after leaving Burlington, VT. Ava enjoys cooking, rock climbing, skiing, and weightlifting.
Education:
Bachelor of Science, Mechanical Engineering, The University of Vermont
See What We’ve Been Working On
View some of the engineering projects our team has designed locally, in the state of Colorado, and across the country. We’ve created solutions for commercial, retail, food service, multi-family housing, healthcare, renovation, hospitality, government, industrial, laboratory, and tenant finish projects.
Contact Our Denver Team
We consider projects of all sizes across the state of Colorado and beyond. Talk to our team to see if RJA is right for your next engineering project.
OUR CERTIFICATIONS
- Professional Engineering
- MBE, DBE, SBE, EBE
- Member of the AABC Commissioning Group
- CXA Certified Commissioning Agents
- Certifiably Green Denver
OFFICES & CONTACT