Carbon Smart™ Indoor Sauna Kit — 4’ × 4’ × 8’
This is a DIY indoor sauna room kit from Finnish Sauna Builders' Carbon Smart™ line. The kit arrives with all interior components precisely cut to your room dimensions — walls, ceiling, benches, door, flooring, vents, and accessories — ready for installation into your framed and wired space. Wood is Thermo Poplar throughout, a thermally modified wood processed without added chemicals. Choose your bench configuration, accessory package, and heater at checkout.
What’s Included
- Foil vapor barrier
- Ergonomic backrests (shipped flat; on-site spacers can be added for angled pitch)
- 1×4 tongue & groove boards — walls and ceiling, Thermo Poplar
- Clear 1×4 bench boards with supports — 20″ deep, Thermo Poplar, custom-built to your chosen configuration
- Corner moldings — walls, ceiling, and baseboards, Thermo Poplar
-
All-glass sauna door with wood handles and trim
- Frame: 27.2″ × 78.7″ (690 × 2000 mm)
- Glass: 24.4″ × 77.3″ (620 × 1963 mm)
- Frame thickness: 1.65″ × 3.6″ (42 × 92 mm)
- Rough opening required: 28″ × 80″
- Duckboard flooring — walk area, Thermo Poplar
- Upper and lower vent grills
- Traditional sauna bucket with liner and ladle
- Sauna thermometer
- Headrest
- Marine-grade, wall-mount, vapor-proof sauna light
- Detailed installation instructions
Note: Shipment includes an all-glass door; some product photos may show a glass wall for reference. Backrests are shipped flat; if you’d like an angled backrest, additional spacers can be easily created on-site to achieve your desired pitch.
Wood — Thermo Poplar
All Carbon Smart™ interior components are Thermo Poplar — a sustainably sourced wood thermally modified at approximately 374°F using steam under atmospheric pressure, with no added chemicals. The process improves dimensional stability, reduces equilibrium moisture content, and enhances resistance to humidity and temperature fluctuations. Suitable for indoor sauna environments.
Customization Options
- Bench configuration — select from layouts shown in product images
- Accessory package — No Accessories, Bench Skirting, LED Under Bench Lighting, or Luxury Package (Skirting + LED Under Bench Lighting)
- Heater — No Heater, Harvia KIP45W 4.5kW WiFi, or HUUM Cliff Mini 3.5kW WiFi (see comparison chart below)
Installation Requirements
- Customer-supplied: framing, insulation, electrical wiring, and exterior wall covering
- Ceiling height: 8 feet recommended per manufacturer safety and clearance guidelines; contact support for custom ceiling heights
- Electrical: requirements depend on the heater selected; refer to each heater model’s individual specifications for voltage, wattage, and circuit requirements before installation
- Weight: 800 lbs; verify floor load capacity before installation
Specifications
| Brand | Carbon Smart™ by Finnish Sauna Builders |
| Kit size | 4’ × 4’ × 8’ |
| Wood | Thermo Poplar (thermally modified, no added chemicals) |
| Door rough opening | 28″ × 80″ |
| Bench depth | 20″ |
| Kit weight | 800 lbs |
| Heater options | No Heater, Harvia KIP45W 4.5kW WiFi, or HUUM Cliff Mini 3.5kW WiFi (see chart below) |
| Certifications | See individual heater model specifications |
Shipping and Returns
- Shipping: see our Shipping Policy for delivery windows, method, and full details.
- Returns: 30-day return window; item must be unused and in original packaging. Damage must be reported within 48 hours of delivery. A 25% restocking fee applies to approved returns. See our Return Policy for full details.
Common Questions
What does the kit include?
The Carbon Smart™ kit includes all interior components: T&G wall and ceiling boards, bench boards with supports, corner moldings, all-glass door with hardware, duckboard flooring, vent grills, foil vapor barrier, backrests, headrest, sauna bucket with liner and ladle, thermometer, vapor-proof light, and installation instructions. Framing, insulation, electrical wiring, and exterior wall covering are customer-supplied.
Does the kit include a heater?
A heater is optional. You can select No Heater, the Harvia KIP45W 4.5kW WiFi, or the HUUM Cliff Mini 3.5kW WiFi at checkout. All heater options include stones; the HUUM Cliff Mini also includes a protective railing. Electrical requirements vary by model — refer to each model’s individual specifications.
What electrical work is required?
Electrical requirements depend on the heater model selected. Refer to the individual heater model specifications for voltage, wattage, and dedicated circuit requirements. A licensed electrician should verify your installation meets local electrical codes before use.
What is the return policy?
Serene Lifestyle Co accepts returns within 30 days of delivery. The item must be unused and in its original packaging. Damage must be reported within 48 hours of delivery. A 25% restocking fee applies to approved returns. See our Return Policy for full details.
Sauna Heater Comparison Chart
| Feature | Harvia KIP45B 4.5KW | Harvia KIP45W 4.5KW | HUUM Cliff Mini 3.5KW |
|---|---|---|---|
| Product Image |  |
 |
 |
| Power Output | 4.5 KW | 4.5 KW | 3.5 KW |
| Cubic Feet Coverage | 176 – 353 cu ft | 176 – 353 cu ft | 106 – 247 cu ft |
| Control Type | Built-in Control | WiFi Control | WiFi Control |
| WiFi Connectivity | ❌ No | ✅ Yes | ✅ Yes |
| Heater Stones Included | ✅ Yes | ✅ Yes | ✅ Yes |
| Railing Included | ❌ No | ❌ No | ✅ Yes |
| Brand | Harvia | Harvia | HUUM |
| Model | KIP45B | KIP45W | Cliff Mini |
| Remote Control | Manual only | App-based via WiFi | App-based via WiFi |
Harvia KIP45B 4.5KW
Harvia KIP45W 4.5KW WiFi
HUUM Cliff Mini 3.5KW WiFi
Key Differences Between Heater Models
- Harvia KIP45B & KIP45W: 4.5 KW, suitable for 176–353 cu ft
- HUUM Cliff Mini: 3.5 KW, suitable for 106–247 cu ft
- KIP45B: built-in manual control only, no WiFi
- KIP45W & HUUM Cliff Mini: WiFi-enabled, app-based control and scheduling
- HUUM Cliff Mini is the only model that includes a protective railing; all models include heater stones
Safety and Installation Notice
Installation must comply with local building and electrical codes. Electrical requirements vary by heater model; consult a licensed electrician before installation. Verify floor load capacity before placing the assembled kit. Specifications are provided by the manufacturer; verify site requirements before purchase.
The information presented on this page is for general wellness and educational purposes only. Statements regarding products sold by Serene Lifestyle Co have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease. Consult a qualified healthcare provider before beginning any new wellness routine, especially if you are pregnant, nursing, or have a pre-existing medical condition.
