The Carbon Smart™ Indoor Sauna Kit in the 4 ft × 7 ft × 8 ft configuration gives you a larger footprint for a more spacious sauna experience—without sacrificing the precision-cut quality and complete component package that defines the Carbon Smart™ line. Built from thermally modified Thermo Poplar and shipped with everything needed for the interior finish, this kit is designed for straightforward installation by DIY builders and professional contractors alike.
Why Customers Choose This Kit
- Larger 4 x 7 footprint accommodates more bathers or a more comfortable single-person layout
- Complete interior package—walls, ceiling, benches, door, lighting, and accessories included
- Thermo Poplar wood is thermally modified without chemicals for lasting dimensional stability
- Precision-cut components reduce installation time and on-site waste
- Flexible heater options from no heater to premium WiFi-enabled Harvia models
- Optional accessory packages let you customize the finish level
- Suitable for both residential and light commercial installations
- Detailed installation instructions included
Product Highlights
Spacious 4 x 7 Interior
The additional foot of length compared to the 4×6 configuration provides more bench space and room to move—well suited for households with multiple users or anyone who prefers a more open sauna environment.
Thermo Poplar Interior
All wall boards, ceiling boards, bench boards, and trim are crafted from Thermo Poplar—a sustainably sourced wood thermally modified at approximately 374°F. The process improves dimensional stability and resistance to humidity without the use of chemicals.
All-Glass Sauna Door
The kit includes a full all-glass door with wood handles and trim. Frame dimensions are 27.2″ × 78.7″ (690 × 2000 mm); rough opening required is 28″ × 80″.
Foil Vapor Barrier
A foil vapor barrier is included to protect the wall structure from moisture migration—an essential component for long-term sauna performance.
Ventilation System
Upper and lower vent grills are included to support proper air circulation throughout the sauna session.
Marine-Grade Vapor-Proof Lighting
A wall-mount, marine-grade, vapor-proof sauna light is included—rated for the high-heat, high-humidity sauna environment.
Flexible Heater Upgrades
Choose from six Harvia 6KW electric heater options at checkout, ranging from built-in manual controls to WiFi-enabled models with app-based scheduling. All heater options include sauna stones.
What's Included
- Foil vapor barrier
- 1×4 tongue-and-groove wall and ceiling boards (Thermo Poplar)
- Clear 1×4 bench boards with supports, 20″ deep (Thermo Poplar, custom-built to your chosen configuration)
- Corner moldings for walls, ceiling, and baseboards (Thermo Poplar)
- Ergonomic backrests
- All-glass sauna door with wood handles and trim (frame: 27.2″ × 78.7″; rough opening: 28″ × 80″)
- Duckboard flooring for 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: Some product photos may show a glass wall for reference; your shipment includes an all-glass door. Backrests are shipped flat; angled pitch can be achieved on-site with spacers. Wall boards run horizontally by default; rooms wider than 8 ft will include an interior seam where boards meet.
Specifications
| Interior Dimensions | 4 ft × 7 ft × 8 ft |
|---|---|
| Wood Species | Thermo Poplar (thermally modified) |
| Modification Temperature | Approximately 374°F (chemical-free process) |
| Wall / Ceiling Profile | 1×4 tongue-and-groove |
| Bench Depth | 20 inches |
| Door Frame Dimensions | 27.2″ × 78.7″ (690 × 2000 mm) |
| Door Glass Dimensions | 24.4″ × 77.3″ (620 × 1963 mm) |
| Door Frame Thickness | 1.65″ × 3.6″ (42 × 92 mm) |
| Rough Opening Required | 28″ × 80″ |
| Recommended Ceiling Height | 8 feet |
| Heater Options | No Heater, or Harvia 6KW (6 models available) |
| Accessory Packages | No Accessories, Bench Skirting, LED Under Bench Lighting, Luxury Package (Skirting + LED) |
| Shipping Weight (approx.) | 800 lbs |
Sauna Heater Comparison
| Feature | Harvia KIP60W 6KW | Harvia KIP60B 6KW | Harvia Cilindro PC60 6KW | Harvia Cilindro PC60E 6KW | Harvia Spirit 6KW | Harvia Virta 6KW |
|---|---|---|---|---|---|---|
| Product Image |  |
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| Power Output | 6 KW | 6 KW | 6 KW | 6 KW | 6 KW | 6 KW |
| Control Type | WiFi Control | Built-in Control | Built-in Control | WiFi Control | WiFi Control | WiFi Control |
| WiFi Connectivity | Yes | No | No | Yes | Yes | Yes |
| Heater Stones Included | Yes | Yes | Yes | Yes | Yes | Yes |
| Railing Included | No | No | No | No | No | Yes |
| Model Series | KIP Series | KIP Series | Cilindro Series | Cilindro Series | Spirit Series | Virta Series |
| Remote Control | App-based via WiFi | Manual only | Manual only | App-based via WiFi | App-based via WiFi | App-based via WiFi |
Harvia KIP60W 6KW WiFi
Harvia KIP60B 6KW Built-in
Harvia Cilindro PC60 6KW Built-in
Harvia Cilindro PC60E 6KW WiFi
Harvia Spirit 6KW WiFi
Harvia Virta 6KW WiFi + Railing
Key Differences at a Glance
- All heater options deliver 6 KW of heating output
- KIP60B and Cilindro PC60 use a built-in manual control panel—no app or remote required
- KIP60W, Cilindro PC60E, Spirit, and Virta are WiFi-enabled for smartphone scheduling and control
- KIP Series: compact wall-mount profile; Cilindro Series: cylindrical with high stone capacity; Spirit and Virta: modern aesthetic with WiFi
- Harvia Virta is the only model that includes a protective railing
Ideal For
- Households with two or more regular sauna users who want additional bench space
- Homeowners building a dedicated sauna room in a basement, garage, or spare room with a longer footprint available
- DIY builders and professional contractors looking for precision-cut, ready-to-install components
- Residential wellness spaces, home gyms, and personal retreats
- Light commercial applications such as spas, fitness studios, and boutique hotels
- Buyers who want to select their own heater or add one later
Important Information
- Framing, insulation, electrical wiring, and exterior wall covering are not included and must be supplied by the installer.
- Recommended ceiling height is 8 feet per manufacturer safety and clearance guidelines. For custom ceiling heights, contact our support team before ordering.
- Electric sauna heaters require a dedicated electrical circuit. Consult a licensed electrician to confirm your installation meets local electrical code requirements.
- All heater installations should comply with the manufacturer's minimum clearance specifications and applicable local building codes.
- This kit is designed for indoor use only. Do not install in unheated or uninsulated spaces without consulting a qualified contractor.
- Sauna use is not recommended for individuals with certain medical conditions. Consult a qualified healthcare provider before use if you have any health concerns.
Frequently Asked Questions
What does this kit include?
The kit includes all interior sauna components: tongue-and-groove wall and ceiling boards, bench boards and supports, corner moldings, backrests, duckboard flooring, an all-glass door with wood handles and trim, upper and lower vent grills, a foil vapor barrier, a sauna bucket with liner and ladle, a thermometer, a headrest, and a marine-grade vapor-proof light. Detailed installation instructions are also included.
What do I need to supply that is not included?
You will need to supply the structural framing, insulation, electrical wiring, and exterior wall covering. If you select a heater option, a licensed electrician will need to install a dedicated electrical circuit sized to the heater's specifications.
How does the 4 x 7 size compare to the 4 x 6?
The 4×7 configuration adds one foot of length, providing more bench space and a more open feel. It is a good choice for households with two or more regular users or for anyone who prefers additional room to move within the sauna.
Can I order this kit without a heater and add one later?
Yes. Select "No Heater" at checkout to receive the full interior kit without a heater. You can source and install a compatible heater separately at any time.
What is Thermo Poplar and why is it used?
Thermo Poplar is a sustainably sourced wood that has been thermally modified at approximately 374°F. The heat treatment improves the wood's dimensional stability and resistance to humidity and temperature fluctuations—without the use of chemicals. It is well suited for the high-heat, high-humidity environment of a sauna interior.
What rough opening is required for the door?
The all-glass door requires a rough opening of 28″ × 80″. The door frame dimensions are 27.2″ × 78.7″ (690 × 2000 mm).
Can I request a custom ceiling height?
The standard kit is designed for an 8-foot ceiling height per manufacturer safety and clearance guidelines. If your space requires a different ceiling height, please contact our support team before placing your order.
What is the difference between the WiFi and built-in control heater options?
Built-in control models (KIP60B and Cilindro PC60) are operated manually using a control panel on the heater itself. WiFi-enabled models (KIP60W, Cilindro PC60E, Spirit, and Virta) connect to your home network and can be controlled and scheduled via a smartphone app.
Is this kit suitable for commercial use?
Yes. The Carbon Smart™ kit is suitable for light commercial applications including spas, fitness studios, and boutique hotels. For high-traffic commercial environments, contact our team to discuss the appropriate configuration.
The Carbon Smart™ 4 × 7 × 8 Indoor Sauna Kit delivers a complete, well-specified interior package in a size that works for more users and more layouts. Select your accessory package and heater option above to configure your kit and place your order.
Sauna use may not be appropriate for everyone. Consult a qualified healthcare provider before use if you have any medical conditions or health concerns. This product is not intended to diagnose, treat, cure, or prevent any disease or medical condition.