The HUUM CORE Thermo-Aspen is a floor-standing electric sauna heater with a thermally modified aspen wood exterior cladding, available up to 10.5kW. This listing is the heater only. A compatible UKU control unit and sauna stones are sold separately. The CORE Thermo-Aspen is the darkest natural wood option in the CORE series - thermally modified aspen that has been treated at high temperature to produce a deep, rich brown finish that closely resembles the traditional appearance of well-seasoned sauna timber. For sauna rooms designed around the warm, enveloping aesthetic of a traditional Finnish or Nordic sauna - dark timber, amber lighting, aged wood - the CORE Thermo-Aspen delivers a heater exterior that integrates as a natural extension of the sauna's material palette. The CORE Thermo-Aspen Package listing at BathingBrands bundles the heater with a UKU control and stones for a complete single purchase.
Thermal modification - what it means for the wood and the look
Thermal modification is a process in which wood is treated at high temperatures (typically 180-230°C) in a controlled environment, altering the cell structure of the wood to produce a range of changes: a deep, uniform brown colour throughout the wood's cross-section (not a surface stain), improved dimensional stability under humidity changes, and increased resistance to decay and moisture absorption. The process converts some of the sugars and starches in the wood that would otherwise feed biological degradation, making the modified wood more stable in the high-heat, high-humidity environment of a sauna. Thermo-aspen specifically takes the naturally pale, white-grained aspen and transforms it to a deep chocolate or dark tobacco brown that bears little visual resemblance to the original natural aspen. In the sauna room context, thermo-aspen reads as the same rich dark timber tone associated with traditional Finnish sauna benches and wall cladding - a familiar and deeply atmospheric visual signature of the sauna space.
CORE Thermo-Aspen vs CORE Aspen - the same wood, transformed
Both CORE Thermo-Aspen and CORE Aspen use aspen wood for the exterior cladding. Natural aspen (CORE Aspen) is pale cream-to-white - the lightest tone in the CORE range, suited to bright Nordic minimal interiors. Thermo-aspen (CORE Thermo-Aspen) is the same wood after thermal modification - deep rich brown, the darkest natural wood option in the CORE range. The shared species name creates the most likely source of buyer confusion in the CORE lineup. The tones could not be more different in practice: natural aspen is one of the palest commercial wood species; thermo-aspen is one of the richest dark browns achievable through a natural process. Confirm which variant is wanted by tone - pale and light (Aspen) or deep and warm (Thermo-Aspen) - before purchasing.
UKU compatible - control and stones sold separately
The CORE Thermo-Aspen is compatible with both UKU Local Black (on-site digital control) and UKU WiFi (HUUM app remote preheat, scheduling, and monitoring on iOS and Android), both sold separately at BathingBrands. The specific output configuration selected determines room coverage, electrical requirements, and whether a UKU Extension Box is required. Confirm the output level and corresponding electrical specification before ordering. A licensed electrician is required. Do not connect to a GFI/GFCI breaker.
Floor-standing electric sauna heater with thermally modified aspen wood exterior cladding. Up to 10.5kW. Open stainless steel stone basket with deep rich brown thermo-aspen side panels. The darkest natural wood CORE exterior - thermo-aspen brings traditional Finnish sauna timber warmth to the heater form. Suits dark timber, amber-lit, and traditional Nordic sauna interiors. Control (UKU Local Black or WiFi) and sauna stones sold separately. SGS Listed. 5-year warranty (elements excluded). Made in Estonia by HUUM. See CORE Thermo-Aspen Package for complete bundled purchase.
Up to 10.5 kW Thermo-aspen exterior - deep rich brown Thermally modified aspen - darkest natural wood CORE Traditional Finnish sauna timber aesthetic Open stainless steel stone basket Floor-standing UKU control sold separately Stones sold separately CORE Thermo-Aspen Package available SGS Listed 5-year warranty (elements excluded) Made in Estonia by HUUM
Specifications
Electrical
| Maximum output |
Up to 10.5 kW |
| Voltage |
240V / 1-phase or 3-phase |
| Control included |
No - UKU Local Black or WiFi sold separately |
| Certification |
SGS Listed |
Stones and room sizing
| Stones included |
No - sold separately |
| Stone specification |
See Stone Requirements document below |
| Room coverage |
Determined by output level selected |
Design
| Exterior cladding |
Thermally modified aspen wood panels |
| Tone |
Deep rich brown - darkest natural wood CORE exterior |
| Stone basket |
Open stainless steel - stones visible on all sides |
| Mounting |
Floor-standing |
| Origin |
Made in Estonia by HUUM |
CORE exterior options - tone scale
| CORE Aspen |
Pale cream-to-white - lightest natural wood |
| CORE Alder |
Pale warm neutral - natural alder |
| CORE Thermo-Aspen (this) |
Deep rich brown - darkest natural wood |
| CORE Black |
Painted black - darkest overall |
| All variants |
Same stainless basket, open design, up to 10.5kW |
Warranty
| Warranty period |
5 years (elements excluded) |
| SKU |
CORE11-TASP-SS |
What's included
HUUM CORE Thermo-Aspen floor-standing sauna heater with thermally modified aspen exterior
Installation and operation manual
Required (not included): UKU control unit (Local Black or WiFi, sold separately at BathingBrands); sauna stones (sold separately - see Stone Requirements document). A UKU Extension Box may also be required depending on the output level selected. A licensed electrician is required. Do not connect to a GFI/GFCI breaker.
Why the HUUM CORE Thermo-Aspen stands out
Thermo-aspen exterior - traditional sauna timber warmth
Thermally modified aspen has the deep, rich brown tone associated with traditional Finnish and Nordic sauna timber - aged, well-seasoned wood that darkens and warms over years of use in a hot sauna environment. For sauna rooms designed around this traditional aesthetic, the CORE Thermo-Aspen delivers that material character as a heater exterior finish, integrating the heater visually with the dark timber walls and benches of a classic sauna interior.
Thermal modification - stable in sauna conditions
The thermal modification process improves aspen's dimensional stability and resistance to moisture-related movement - important properties for a heater exterior cladding exposed to repeated cycles of high heat and steam. Modified wood is less prone to expansion, contraction, and checking from repeated heating and cooling than unmodified wood, making thermo-aspen a practical as well as aesthetic choice for the sauna environment.
Open basket - stone and wood visible together
The CORE's open stainless steel basket presents the stone mass through the structure on all sides, with the thermo-aspen panels framing the stones in deep brown timber. The visual pairing of dark wood and natural olivine stones is the most traditional of the CORE finish combinations - both materials referencing the visual language of a wood-heated Finnish sauna with a stone mass at its centre.
Darkest natural wood in the CORE range
Within the CORE series, Thermo-Aspen is the darkest natural wood option - darker in tone than Alder (pale warm neutral) and dramatically darker than natural Aspen (pale cream-white). For sauna rooms where the interior palette is dark and warm and the heater should match rather than contrast with surrounding surfaces, the Thermo-Aspen is the appropriate natural wood choice. CORE Black is the only darker option overall.
CORE Thermo-Aspen Package - complete bundled option
The CORE Thermo-Aspen Package listing at BathingBrands bundles the heater with a UKU control and stones for a single complete purchase. This standalone listing is for buyers sourcing the heater separately - replacing a heater in an existing CORE installation, pairing with a specific control already on hand, or completing a multi-component order in separate transactions.
Up to 10.5kW - multiple output configurations
The CORE Thermo-Aspen is available up to 10.5kW across multiple output configurations. The specific output determines room coverage, electrical requirement, and whether the UKU Extension Box is needed. Use the Size Your Sauna document below to confirm the correct output for the specific room before ordering, and confirm panel capacity for the required breaker size with a licensed electrician.
About HUUM
Made in Estonia - SGS Listed
HUUM CORE Thermo-Aspen. Up to 10.5kW. Deep rich brown thermo-aspen exterior. Traditional sauna timber aesthetic.
HUUM is an Estonian sauna heater company. The CORE Thermo-Aspen is HUUM's floor-standing heater with thermally modified aspen wood exterior cladding - the darkest natural wood option in the CORE range, with deep rich brown thermo-aspen panels framing an open stainless steel stone basket. This listing is the heater only. UKU control (Local Black or WiFi) and sauna stones are required and sold separately at BathingBrands. See the CORE Thermo-Aspen Package for a complete bundled purchase. We are an authorized HUUM dealer.
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Thermally modified aspen exterior - deep rich brown, darkest natural wood CORE
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Traditional sauna timber aesthetic - integrates with dark Nordic sauna interiors
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Open stainless steel stone basket - stones visible all sides
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Up to 10.5kW - UKU Local Black or WiFi compatible (sold separately)
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Stones sold separately - CORE Thermo-Aspen Package also available
Manuals and Documents
Warranty
5-year limited warranty (elements excluded)
The HUUM CORE Thermo-Aspen is covered by HUUM's 5-year limited warranty from the date of purchase. The warranty covers defects in manufacturing and materials under normal use conditions. Heating elements are excluded from the 5-year coverage and carry their own separate warranty period. The warranty does not cover damage caused by improper installation, use of incorrect or non-approved stones, operating without the required stone load, or failure to follow HUUM's installation and operating guidelines. A licensed electrician is required for all electrical connections. Do not connect to a GFI/GFCI breaker. Proof of purchase from an authorized HUUM dealer is required. We are an authorized HUUM dealer.
