Onion Flats
Architecture and high-performance consulting shaped by decades of hands-on development, construction, Passive House, and deep-energy-retrofit work.
What they're known for
A rare architecture practice whose Passive House advice comes from having acted as architect, developer, builder, and even prefab manufacturer on its own projects.
Onion Flats Architecture grew out of a Philadelphia development and construction practice and now works from Pennsylvania and Massachusetts on architecture, sustainability consulting, Passive House, modular construction, and deep energy retrofits. Its principals hold Passive House and LEED credentials, while the firm’s history includes developing and building its own high-performance housing. Current work increasingly applies that experience to affordable housing and prefabricated retrofit strategies intended to scale beyond one-off showcase projects.
Capabilities
- Architectural Design
- Building-Science Consulting
- Deep-Energy Retrofit
Performance focus
- Passive House
- Thermal Comfort
- Low-Carbon Construction
Credentials
Certified Passive House professionals on staff
Onion Flats lists Passive House Certified Consultants, Designers, and Tradesmen among its team.
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Sources
Facts verified September 2026. Compound is an independent editorial directory and is not affiliated with this company unless stated.