Overview

CleanFiber manufactures environmentally friendly cellulose insulation from recycled cardboard boxes using a patented chemical treatment process. Based in Buffalo / Lackawanna, NY (founded 2013 as UltraCell Insulation by Jonathan Strimling), the company is a 43North alumnus that scaled a regional plant into a national expansion story. In April 2024 CleanFiber closed a Series B led by Spring Lane Capital — reported as $28M equity in contemporaneous coverage, with the company later citing a $33M Series B — alongside a $31.5M project financing facility from Spring Lane. Participants included Climate Innovation Capital, AXA IM Alts, Ahlström Invest, and Tokyu Construction/Global Brain. In October 2024 CleanFiber announced selection for $20M in U.S. Department of Energy MESC grant funding to support additional production facilities. The company has claimed cumulative capital well above $100M when including project finance, tax credits, and related facilities.

Why CleanFiber is interesting

43North alum manufacturing climate materials in Buffalo — April 2024 Series B (~$28–33M equity) led by Spring Lane Capital plus $31.5M project finance, and later a $20M DOE MESC grant path for multi-state plant expansion.

Product & use cases

Manufactured cellulose insulation produced from recycled cardboard, sold into building insulation channels as a climate-oriented alternative to fiberglass and foam products.

• Residential new construction and retrofit insulation
• Builders seeking recycled-content cellulose products
• Regional and national insulation distributors sourcing plant-made cellulose

Key facts

• 43North alumnus; HQ / manufacturing in Buffalo area (Lackawanna plant)
• Series B (Apr 2024): ~$28–33M equity led by Spring Lane Capital; $31.5M project financing facility
• Series B participants: Climate Innovation Capital, AXA IM Alts, Ahlström Invest, Tokyu Construction/Global Brain
• DOE MESC (Oct 2024): selected for $20M grant funding for additional plants
• Company has described cumulative capital >$100M including project finance / incentives; Inc. 5000 #1 fastest-growing manufacturing (2024, company claim)

Fundraising history

Investors in our directory

Funds linked from CleanFiber's profile — open a fund page for stage focus and related deal articles.

Competitive landscape

Edge: Cardboard-to-cellulose manufacturing at industrial scale in Buffalo, paired with project-finance-friendly expansion rather than only software-style equity rounds.

Building insulation is an incumbent-heavy materials market. CleanFiber competes on recycled cardboard feedstock and manufacturing scale-out, using project finance and public grants alongside venture equity.

• Fiberglass insulation majors (Owens Corning, CertainTeed, etc.) incumbent

  Dominant residential insulation share.

• Other cellulose insulation producers direct

  Traditional cellulose often from newsprint; feedstock and process differ.

• Spray foam insulation adjacent

  Different install method and performance/cost tradeoffs.

Notable stories

• Spring Lane Capital had watched the company for over a decade before leading the 2024 Series B and project facility (TechCrunch, Apr 2024).

Industries

Related funding articles

Venture Capital Tracker pieces that cover CleanFiber's financing or category context.

• Buffalo Startups and VC Firms in 2026: ACV Auctions, 43North, and Life Sciences Capital