Hearthstone Stoves Green Mountain 40 Freestanding Wood Stove

Compact Cast Iron Wood Stove with TruHybrid™ Catalytic Combustion and a Soapstone-Lined Firebox Traditional black cast iron construction with a soapstone-lined firebox, TruHybrid™ catalytic combustion, 79% HHV efficiency, and heating coverage of up to 1,400 square feet. Key Features TruHybrid™ combustion combining primary, secondary, and catalytic tertiary stages for a clean, efficient burn 79% HHV efficiency with EPA-certified emissions of 1.07 g/hr Heats up to 1,400 sq. ft., depending on home layout, insulation, and operating conditions 1.32 cu. ft. soapstone-lined firebox accepting logs up to 16 inches Burn time of up to 16+ hours and HeatLife™ of up to 20 hours, per the current owner's manual Included rear heat shield for reduced rear clearances Large ceramic glass window with an air-wash system for fire viewing Mobile-home approved when installed per the owner's manual, with the outside air kit required Product Features TruHybrid™ Catalytic Combustion The Green Mountain 40 pairs primary and secondary combustion with a tertiary catalytic stage. The stainless steel catalytic combustor becomes active at approximately 500°F and burns smoke and remaining particles that were not fully consumed in the firebox, so a well-established fire produces little to no visible smoke from the chimney. The stove typically operates in the 800°F to 1,300°F catalyst range. Soapstone-Lined Firebox The firebox is lined with natural soapstone blocks. Soapstone absorbs the high heat of the fire and then radiates gentle, even warmth into the room, extending comfortable heat well after the flames die down. Cast Iron Construction The GM40 is styled with clean lines in traditional black cast iron and is built from precision-made cast iron, soapstone, steel, and ceramic components. The 2026 HearthStone catalog identifies the Green Mountain family as EPA-certified room heaters made in Vermont. Simple, Direct Controls A single primary air control under the ash lip regulates the burn rate, a bypass handle routes combustion products through or around the catalyst, and a catalyst thermometer indicates when the stove is in the active catalytic range. Optional Convection Blower with Reduced-Clearance Heat Shield The optional Blower & Reduced Clearance Heatshield Combo (96-57400) moves air up and across the stove to circulate more heat into the room. A snap switch turns the blower on automatically, and a rheostat adjusts its speed. The kit's shield supports the reduced-clearance configurations published in the owner's manual. Outside Air Capability The optional Outside Air Starter (96-53400) connects the stove's air intake to a minimum 3-inch duct (ducting and termination supplied by others) so combustion air is drawn from outside the home. A 3-inch to 4-inch increaser (90-53308) is available when a 4-inch duct is needed. Outside air is required in all mobile-home installations, and Canadian outside-air installations require the stove to be attached to the floor and a damper allowing 100% closure. Available Finish and Configuration Finish Exterior Loading Fuel Part ID MSRP Included Equipment Black Matte Black matte cast iron with soapstone-lined firebox Front load Wood 8640-0010 $3,499.00 Stove with rear heat shield and catalyst thermometer; owner's manual Specifications Specification Value Combustion system TruHybrid™ — primary, secondary, and catalytic tertiary combustion Catalytic combustor Applied Ceramics ACI-6M2 stainless steel catalyst HHV efficiency 79% (weighted average, higher heating value) EPA-certified emissions 1.07 g/hr Maximum heat output Up to 40,000 BTU/hr of cordwood (independent laboratory test results) EPA tested heat output 14,000 to 24,000 BTU output under specific test conditions Heating capacity Up to 1,400 sq. ft.; factors unique to your home can reduce coverage Firebox capacity 1.32 cu. ft. Maximum log length Up to 16" Burn time Up to 16+ hours (per current owner's manual) HeatLife™ Up to 20 hours (per current owner's manual) Height 30⅜" Width 23¼" Depth 19⅜" Weight 350 lb Flue exit Top, 6" diameter Chimney connector 6" diameter, 24 or 25 MSG blued steel (single wall) or listed double-wall connector Chimney Listed Type HT (UL 103 / ULC S629) metal chimney, 6" inside diameter, or code-approved lined masonry chimney with 6" round or 8" x 8" square flue Fuel Natural seasoned cordwood only Certification EPA 2020 certified; conforms to UL 1482-2022; certified to ULC S627-2021 (PFS Report F17-183) Finish Black Matte Clearances and Hearth Requirements Clearances to combustibles. Dimensions are measured from the body of the stove unless otherwise indicated; C, D, and F are chimney-connector reference dimensions. Refer to the current owner's manual for complete installation requirements. Connector Configuration A — Side (stove body to side wall) B — Rear (stove body to rear wall) C — Connector to rear wall D — Connector to side wall E — Corner (stove body to corner wall) F — Corner (connector to corner wall) Single wall, no rear heat shield 14" 16" 21" 25½" 14" 25½" Single wall with included rear heat shield 14" 13¾" 18" 25½" 7" 17¼" Single wall with blower kit heat shield (96-57400) 14" 13¾" 18" 25½" 7" 17¼" Double wall with included rear heat shield 14" 9¾" 14" 25½" 7" 17¼" Double wall with blower kit heat shield (96-57400) 14" 9¾" 14" 25½" 7" 17¼" Alcove installations. Alcove side, rear, and connector clearances (A through D) match the corresponding shielded configurations above; corner dimensions E and F in an alcove follow NFPA 211. The minimum unprotected alcove width is 51¼", and the minimum alcove ceiling height from the floor is 56" with either a single-wall or double-wall connector. For protected surfaces, refer to NFPA 211 and your local authority having jurisdiction. Chimney connector clearances (through-wall, top flue exit). With either the included rear heat shield or the blower kit shield installed: single-wall connector — 13¾" from the appliance rear to the wall and 18" from the vertical connector to the wall; double-wall connector — 9¾" and 14" respectively. Single-wall connector pipe requires 18" to an unprotected ceiling or 9" to a protected ceiling; for double-wall pipe ceiling clearance, refer to the pipe manufacturer's specifications. Hearth and floor protection. The Green Mountain 40 does not require an insulated hearth pad; noncombustible ember protection with no R-value requirement must cover the floor beneath and around the stove. Requirement USA Canada Minimum overall floor protection (width x depth) 31½" x 33" 40" x 43" Front extension (from edge of fuel-door opening to edge of hearth) 16" 18" Side extension 8" from edge of fuel-door opening 8" from stove body Rear extension 0" from stove body 8" from stove body Luxury vinyl plank (LVP) or luxury vinyl tile (LVT) flooring requires extra consideration; some vinyl flooring begins to warp at 110°F. Consult the flooring manufacturer for maximum temperature recommendations, as additional shielding may be necessary. Trim and mantel. The owner's manual publishes a 6" side trim clearance, a mantel height of 48" from the floor with a maximum mantel depth of 12", and a 4" trim thickness reference. The Green Mountain 40 is a freestanding room heater and is not to be installed in any factory-built fireplace. Chimney and draft. The stove connects to a 6" listed Type HT metal chimney or a code-approved lined masonry chimney. The recommended minimum chimney height for a top-of-stove installation is 16 feet from the floor, and the recommended maximum chimney height is 30 feet. Proper chimney draft is required for safe, efficient operation; follow the current owner's manual and the chimney manufacturer's requirements, and note that installations with excessive draft may require a stovepipe damper. Mobile-home installations. Install in accordance with 24 CFR Part 3280. The outside air kit (96-53400) is required, the stove must be permanently attached to the floor using the shipping clips supplied with the stove, and a Mobile Home Chimney & Connector Kit conforming to UL 103 or ULC S629 must be used, including a stainless spark-arrester cap, storm collar, and adjustable vented flashing. Do not install in a sleeping room, maintain the structural integrity of the home, burn wood only, keep the front door closed during operation except for startup and loading, remove the chimney when transporting the home, and preserve the exterior vapor barrier where the chimney penetrates the structure. Included Equipment Green Mountain 40 Model 8640 woodstove with catalytic combustor, rear heat shield (5640-024), and catalyst thermometer (7200-520) installed Owner's manual Shipping clips (used for floor attachment in Canadian outside-air and mobile-home installations) Compatible Accessories Accessory Part ID MSRP Compatibility / Requirement Blower & Reduced Clearance Heatshield Combo 96-57400 $649.00 Optional convection blower with heat shield; supports the reduced-clearance blower kit shield configurations in the owner's manual Outside Air Starter 96-53400 $109.00 Optional for most installations; required for all mobile-home installations; connects to a minimum 3" duct supplied by others 3" to 4" Outside Air Increaser 90-53308 $49.00 Use with the outside air system (96-53400) when a 4" duct connection is required Warranty The Green Mountain 40 is covered by HearthStone's written limited warranty, under which the term Limited Lifetime is defined as 10 years from the start of coverage. Stone and cast iron components carry Limited Lifetime coverage, steel components and door handles and latches are covered for 5 years, and glass, accessories, and the enamel finish are covered for 1 year, with labor coverage during the first year for dealer-installed appliances. The catalytic combustor (Applied Ceramics model ACI-6M2) is warranted directly by Applied Ceramics, including no-charge replacement within the first two years and a prorated schedule thereafter. All coverage is subject to the terms, conditions, and exclusions of the current written warranty, and warranty registration is available at hearthstonestoves.com. About HearthStone Hearthstone Quality Home Heating Products, Inc. is based in Morrisville, Vermont, where the company builds soapstone and cast iron heating products designed for long, comfortable, even heat. Visit our showroom to see the Green Mountain 40 in person and talk through your installation with our team.