The Kozy Heat Chaska 335S is the premium variant of Kozy Heat's slim-profile gas insert line — engineered to drop into existing masonry fireplaces (including older shallow openings most inserts can't fit) while delivering the highest efficiency rating in the entire Kozy Heat insert lineup at 80% on natural gas. With a modulating 22,000 to 36,000 BTU/hr burner, just 16 inches of depth, and fan kit, co-linear venting kit, millivolt valve system, and traditional brick lining all included as standard features, the Chaska 335S is the right answer for customers who want maximum efficiency, premium standard features, and the ability to fit existing shallow fireplace cavities — without paying à la carte for upgrades. What Makes the Chaska 335S Different 80% efficiency is the headline number. The Chaska 335S is the highest-efficiency gas insert in the Kozy Heat lineup — higher than the Chaska 34 (77%), the Nordik 34i, and even the Springfield 36 wall-mounted retrofit (79.5%) when measured on natural gas. At 80% efficiency, 80 cents of every dollar spent on gas becomes usable heat in your room. Combined with the modulating burner that adjusts continuously between 22,000 and 36,000 BTU/hr based on demand, the Chaska 335S is designed for long-term operating cost minimization, not just initial purchase price. The Chaska 335S sits at the premium end of Kozy Heat's dedicated insert lineup. Compared to the Chaska 34 (same slim-profile form factor), the 335S includes as standard features what the Chaska 34 typically requires as separate purchases: Feature Chaska 335S Chaska 34 Fan Kit Included standard Optional (sold separately) Co-Linear Vent Kit Included standard (3" combustion air / 3" exhaust) Sold separately Millivolt Valve System Included standard Configuration-dependent Traditional Brick Lining Included standard Optional upgrade Upper Hood & Lower Grill Included standard Optional accessory Efficiency (NG) 80.0% 77.0% BTU Range (NG) 22,000–36,000 modulating 18,500–34,000 modulating If you've been comparing slim-profile gas inserts and finding that the price differences between models are mostly explained by what's "included" vs "sold separately," the Chaska 335S is the option that packages everything together — the math typically favors this approach unless you're certain you won't want the fan kit or premium refractory. Will the Chaska 335S Fit Your Fireplace? This is the most important question for any gas insert purchase, and the one to answer BEFORE ordering. The Chaska 335S's slim 16-inch depth is its key advantage — it fits existing masonry fireplaces that won't accommodate deeper inserts. Minimum specifications for the existing fireplace opening: Existing Fireplace Requirement Minimum Opening width At least 33-1/2" Opening height At least 23-1/2" Opening depth At least 16-1/2" (the Chaska 335S's key advantage — many other inserts require 20"+ depth) Chimney condition Solid-fuel masonry or factory-built non-combustible chimney in good structural condition; must be able to accept 3" co-linear vent piping Hearth/floor protection Non-combustible hearth in front of the fireplace per local code requirements Gas line access Existing gas line or ability to route a new gas line to the insert location Specifications Brand Kozy Heat Model Chaska 335S SKU CSK-335S Product Type Direct Vent Gas Fireplace Insert BTU Input (Natural Gas) 22,000 – 36,000 BTU/hr (modulating) BTU Input (Liquid Propane) 22,000 – 36,500 BTU/hr (modulating) Efficiency (Natural Gas) 80.0% Efficiency (Liquid Propane) 76.2% Vent Type Direct Vent (Co-linear through existing chimney; 3" combustion air / 3" exhaust) Vent Kit Included standard Fuel Type Natural Gas or Liquid Propane (specify at order; conversion kits available) Overall Width 33-3/8 in. Overall Height 23 in. Overall Depth 16 in. (slim profile) Weight 150 lbs. Viewing Area 29-3/8 in. (W) × 15-13/16 in. (H) Glass Ceramic Burner Type Modulating (continuous BTU adjustment) Valve System Millivolt (standard — operates without household electricity) Fan Kit Included standard Brick Lining Traditional brick refractory (standard) Upper Hood & Lower Grill Standard Screen Front Options 9 different styles available in variety of colors Refractory Options Multiple alternatives to traditional brick Bedroom Approved Yes (direct vent design) Min Fireplace Width 33-1/2 in. Min Fireplace Height 23-1/2 in. Min Fireplace Depth 16-1/2 in. Warranty Limited Lifetime Warranty Estimated Heating Area Up to ~1,300 sq. ft. (varies by insulation, ceiling height, climate) Made In USA (Hussong Manufacturing, Minnesota) Available Options & Accessories Most key features come standard on the Chaska 335S. The decisions you make during the order process focus on style and aesthetic choices: Fuel Type — Natural Gas or Liquid Propane (specified at order; conversion kits available) Screen Front Style — 9 different screen front options in a variety of colors, ranging from traditional ornate patterns to contemporary minimalist designs Refractory Choice — Traditional brick (standard) or alternative refractory finishes for different interior aesthetics Shroud Trim — decorative metal frame integrating the insert with your existing fireplace surround; multiple style options available Decorative Fronts / Surrounds — exterior trim around the firebox opening. Browse our Fireplace Fronts collection for additional compatible styles. Remote Control Options — basic on/off remote, thermostat remote, or programmable remote options available For configuration assistance — choosing the right screen front, refractory, and shroud combination for your interior — contact us. We do this every day. Brand Kozy Heat®
