HearthStone GMi 70 Green Mountain Wood Insert

The HearthStone GMi 70 turns an existing fireplace into a wood heater with a clean, built-in look. Its cast iron front is designed to fit flush with your hearth, so the insert reads as part of the fireplace instead of a box sitting in front of it.

Running it is simple. A single lever controls the air, so you can burn hot and fast or turn it down low and slow for a longer burn. The non-catalytic firebox holds 2.4 cubic feet and takes logs up to 20 inches, and the blower comes factory installed. Choose matte black or brown enamel.

What Makes the GMi 70 Different

• Flush cast iron front. The front sits flush with the hearth for a finished look that suits traditional and newer rooms alike.
• One-lever control. A single air lever handles everything from a quick hot fire to a slow overnight burn.
• Blower included. The blower comes installed, so you don't need to add it later.
• Two finishes. Pick matte black or HearthStone's brown enamel to suit the room.

This listing is the HearthStone GMi 70 (Green Mountain Insert 70) non-catalytic wood insert, model 8450, offered in matte black (8450-0010) and brown enamel (8450-0020).

Key Specifications

• Combustion: Non-catalytic
• Minimum fireplace opening: 29 in W x 24 in H x 16 in D (with optional surround extension)
• Firebox capacity: 2.4 cu ft
• Maximum log length: 20 in
• Flue size: 6 in, top exit
• Blower: Included, factory installed
• EPA certification: 2020 particulate emissions standard
• Dimensions (W x D x H): 33 1/2 in x 19 5/8 in x 25 3/4 in
• HeatLife (HearthStone rating): 10 hours

HeatLife is HearthStone's own burn-time rating. Actual results depend on your fireplace, chimney, wood, and how the insert is run.

Ownership & Maintenance

Because the GMi 70 is non-catalytic, there's no combustor to replace. Hearth Doctor customers get support after the sale.

Every fireplace is different, and we'll help you confirm fit before you choose an insert. Browse more wood inserts or visit our Auburn, Brunswick, and Yarmouth showrooms to talk through fit, liner, and installation.