Business Details
21 Years
experience
Award-Winning Sustainable Architects in Philadelphia
Founded in 1997, we are an award-winning architecture practice dedicated to sustainable, high-performance design. Our team combines decades of experience in architecture, construction, and development with specialized credentials in Passive House and LEED certifications. We deliver innovative solutions for new construction, adaptive reuse, and deep energy retrofits, prioritizing resilience, equity, and replicability. Our integrated approach bridges design and construction, ensuring on-time delivery of cost-effective, energy-efficient buildings.We champion low-carbon strategies through modular construction, net-zero-ready designs, and hands-on expertise in high-performance building envelopes. As educators and industry leaders, we collaborate with clients to achieve ambitious sustainability goals while addressing community needs. Our work spans multifamily housing, institutional projects, and historic renovations, setting benchmarks for sustainable urban living nationwide.
Services
Architectural Design
Sustainability Consulting
Passive House Certification
Deep Energy Retrofit
Modular Construction
LEED Certification
Net-Zero Building
Energy Modeling
Historic Renovation
Affordable Housing
Details
- Year established: 2005
Highlights and features
- We offer 30+ years of combined experience in Passive House and Net-Zero construction.
- Our integrated design-build approach ensures seamless project delivery.
- We hold multiple industry certifications, including LEED, PHIUS, and PHI.
- Our team includes architects, developers, and builders with hands-on expertise.
- We pioneered Philadelphia's first LEED Platinum and Passive House projects.
Associations and certifications
- LEED AP
- CPHC
- CPHD
- PHIUS
- PHI
What people say
Award-winning designs
Collaborative team
Energy-efficient expertise
Timely delivery
Hands-on experience
Services
Architectural Design
We create innovative, high-performance buildings tailored to client needs. Our designs integrate sustainable materials, energy efficiency, and functional aesthetics. With expertise in multifamily housing, institutional projects, and historic renovations, we deliver spaces that enhance occupant health and reduce environmental impact while meeting strict budget and timeline requirements.
Passive House Certification
Our team specializes in Passive House standards for ultra-low energy buildings. We guide projects through certification, ensuring airtight construction, thermal bridge-free design, and high-efficiency ventilation. This approach reduces energy use by up to 90% compared to conventional buildings while maintaining superior indoor air quality and comfort.
Deep Energy Retrofit
We transform existing structures into high-performance buildings through comprehensive retrofits. Our solutions include envelope upgrades, HVAC optimization, and renewable energy integration. By leveraging prefabricated components and advanced modeling tools, we achieve 70-90% energy reductions while preserving structural integrity and minimizing disruption to occupants.
Modular Construction
Our modular construction services combine off-site fabrication with sustainable design. We optimize panelized systems for rapid assembly, reducing construction timelines by 30-50%. This method improves quality control, minimizes waste, and enables scalable solutions for multifamily housing, commercial spaces, and institutional buildings while maintaining Passive House performance standards.
Sustainability Consulting
We provide expert guidance on achieving sustainability goals through LEED certification, energy modeling, and material selection. Our consultants help clients navigate green building codes, optimize building performance, and implement cost-effective strategies. Services include lifecycle analysis, carbon footprint reduction, and compliance with evolving environmental regulations.
People
Timothy McDonald
Principal Architect
Licensed architect with 25+ years in sustainable design. Co-founded Onion Flats in 2005. Certified Passive House Consultant and LEED AP. Combines technical expertise with construction management experience to deliver resilient, low-carbon buildings.
Howard Steinberg
Principal Architect
Registered architect with 30+ years in Mid-Atlantic projects. LEED AP and Certified Passive House Designer. Focuses on client-driven solutions integrating sustainability and innovation. Co-founder of Onion Flats and JIG, Inc.
Kara Haggerty Wilson
Design Director
Certified Passive House Designer specializing in affordable housing. Expertise in energy modeling and high-performance building envelopes. Translates sustainability goals into actionable strategies while maintaining cost-effectiveness and design integrity.
Dan Addis
Project Manager
Manages diverse projects from restaurants to multifamily housing. Skilled in construction administration and field coordination. Ensures project success through proactive problem-solving and attention to detail in detailing and trade coordination.
Jeannette Penniman
Project Manager
Registered architect with experience in education, residential, and historic projects. Certified Passive House Consultant focused on low-carbon strategies. Active in advancing sustainable practices through BuildGreenCT and client-focused project delivery.
Questions
What architectural services do you specialize in?
We specialize in sustainable architectural design, Passive House certification, Deep Energy Retrofits, modular construction, and LEED certification for multifamily, institutional, and historic projects.
Are you certified in green building standards?
Yes, our team holds LEED AP, Certified Passive House Consultant (CPHC), and Certified Passive House Designer (CPHD) credentials from PHIUS and PHI.
How do you approach energy-efficient building design?
We integrate Passive House principles, high-performance envelopes, and modular construction. Our methods reduce energy use by 70-90% while maintaining occupant comfort and building durability.
What regions do you serve?
We operate primarily in Pennsylvania and Massachusetts, with projects across the Northeast United States and national consulting capabilities for modular and retrofit solutions.
Can you help with existing building retrofits?
Yes, we specialize in Deep Energy Retrofits, transforming inefficient buildings into high-performance spaces with prefabricated components and advanced energy modeling tools.
How do you ensure project timelines and budgets?
Our integrated design-build approach combines in-house construction expertise with modular strategies, reducing timelines by 30-50% and minimizing cost overruns through precise planning and execution.
