The Osburn 3500 is the powerhouse of the lineup, designed for those who demand maximum heat and efficiency. With its 3.5 ft³ firebox, 110,000 BTU/h maximum output, and a 144 CFM blower, this insert easily warms large spaces while maintaining low emissions at just 1.6 g/h. Its expansive glass viewing area offers a stunning fire view, while customizable overlays, faceplates, and trims let you tailor the look to your home. Built with durable Canadian craftsmanship, the 3500 delivers performance and elegance that no winter can withstand.

Key Specs:

• Heating area: 1,000 – 2,700 ft²
• Firebox volume: 3.5 ft³ (2.88 ft³ EPA tested)
• Max burn time: 10 hours
• Max heat output: 110,000 BTU/h
• Efficiency: 71% (HHV), up to 77% optimal
• Emissions: 1.6 g/h
• CO emissions: 73 g/h
• Max log length: 22" (load over width & depth)
• Chimney: 6" diameter, 15' minimum height
• Blower: 144 CFM (included)
• Combustion: Non-catalytic, EPA 2020 approved
• Baffle: C-Cast or equivalent
• Door: Cast iron with ceramic glass
• Glass dimensions: 18 ⅞" × 11 ¾"
• Glass air-wash system: Yes
• Firebox lined with refractory bricks: Yes
• Stainless-steel secondary-air system: Yes
• Steel thickness: 3/16" body, 5/16" top
• Overall dimensions (H × W × D): 24 ⅞" × 30 ⅜" × 29"
• Fireplace opening minimum: 26 ¼" H × 31" W × 18 ⅜" D
• Warranty: Limited lifetime