When selecting exterior siding, cladding, or architectural accents, species selection plays a critical role in overall project performance. Factors such as grain pattern, aesthetic character, durability, and long-term dimensional stability all influence how a material performs in exterior environments. For certain wood species, thermal modification is a process that can enhance key performance characteristics—including resistance to moisture, biological decay, and dimensional movement—without the use of chemical preservatives.

To provide transparent, data-backed insight into how thermally modified wood performs, Montana Timber Product’s samples of thermally modified Southern Yellow Pine and Western Hemlock were evaluated through independent laboratory testing by the LSU AgCenter Wood Durability Laboratory.

The results (Report #WDL-2025-03b) demonstrates how the thermal modification process enhances the baseline characteristics of these specific species without the use of chemical preservatives.

Here is a breakdown of the data, verified by ASTM and AWPA standards.

PILLAR ONE

Rot and Insect Resistance – Testing Thermally Modified Pine & Hemlock

Fungi and insects are common considerations for any exterior wood application. The LSU AgCenter testing utilized standardized methods to evaluate how the thermal modification process alters the wood’s performance in these areas.

Fungal Decay & Rot Resistance in Thermally Modified Wood (AWPA E10)

Fungi require moisture and wood sugars to thrive. The thermal modification process alters these natural sugars, making the wood less susceptible to rot.

During the 12-week fungal decay test, the unmodified pine samples experienced a 55% weight loss. In contrast, the thermally modified samples demonstrated minimal weight loss.

The Data:

• Unmodified Southern Yellow Pine: 55% weight loss
• Thermally Modified Southern Yellow Pine: 5% weight loss
• Thermally Modified Western Hemlock: 2% weight loss

The Takeaway: Thermal modification achieved up to a ~95% reduction in fungal decay compared to unmodified Southern Yellow Pine, providing enhanced resistance to brown and white rot fungi.

Termite Resistance of Thermally Modified Southern Yellow Pine (AWPA E1)

Because thermal modification alters the nutritional content of the wood, it can affect termite feeding behavior. In laboratory “no-choice” tests, the modified wood showed improved resistance, particularly in Southern Yellow Pine.

• Unmodified Southern Yellow Pine: 83.94% weight loss
• Thermally Modified Southern Yellow Pine: 21.24% weight loss

The Takeaway: The thermal modification process resulted in a ~75% reduction in weight loss for Southern Yellow Pine compared to its unmodified counterpart. (Note: Performance in termite exposure is species-dependent; modified Western Hemlock performs at standard levels, making it best suited for elevated, vertical cladding applications where ground contact is avoided).

PILLAR TWO

Moisture & Dimensional Stability of Thermally Modified Siding

True exterior performance goes beyond rot and insect resistance. To ensure long-term success, the wood must also remain stable and strong through years of shifting weather and seasonal moisture.

Dimensional Stability: Reducing Moisture Uptake and Shrinkage

Wood naturally absorbs and releases moisture depending on the environment. The thermal modification process lowers the equilibrium moisture content of SYP and Hemlock, meaning these specific species take on less water than they would in their unmodified state.

The Takeaway: The test data indicates reduced radial and tangential shrinkage for these modified species. This lower equilibrium moisture content helps the wood maintain its shape and minimizes seasonal movement once installed.

PILLAR THREE

Structural Integrity & Bending Strength (ASTM D143)

A common question regarding modified wood is how the heating process impacts its structural strength. Testing for Bending Strength (MOR) and Stiffness (MOE) showed that the thermally modified wood performs comparably to unmodified SYP and Hemlock.

The Takeaway: Thermal modification did not significantly reduce the wood’s bending modulus or strength. It maintains the necessary structural integrity required for standard exterior cladding and siding applications.

Summary: Testing Establishes Proven Performance for Thermally Modified SYP & Hemlock Siding

The independent LSU AgCenter testing results confirm that thermally modified Southern Yellow Pine and Western Hemlock provide a reliable, high-performance alternative to chemically treated lumber.

By choosing these modified species for your next project, you are selecting a natural product that offers:

• Enhanced resistance to fungal decay compared to unmodified SYP/Hemlock.
• Improved termite resistance in Southern Yellow Pine.
• Reduced moisture uptake and dimensional movement.
• Maintained bending strength and stiffness.

Download the Full LSU Laboratory Report (PDF)

Request a Thermally Modified Sample Kit

Illustrations generated with AI (Google Gemini) based on LSU AgCenter test data.

Featuring Thermally Modified Hemlock Siding & CVG Cedar Interior

This renovated Bellevue, Washington home proves that even a 1960s split-level can be reborn. Originally described by RRA Architecture as “dark, disjointed, and inefficient,” the home was completely reimagined by the architects and RW Anderson Construction. The project features Montana Timber Products’ ranchwood™ Artisan and AquaFir™ lines, which were key in the remodel to creating a bright, open, and inviting space.

PROJECT DETAILS

Location: Bellevue, Washington
Design: RRA Architecture
Build: RW Anderson Construction
Photographer: Kirk Hostetter

PRODUCTS & APPLICATIONS

	Exterior Siding	Soffit & Ceiling
Species	Thermally Modified CVG Hemlock	CVG Cedar
Dimensions & Profile	1″ × 6″, Random Lengths (8′–16′), Tex-Gap	1″ × 6″, Random Lengths (8′–16′), Tongue & Groove
Product	ranchwood™ Artisan	AquaFir™
Texture / Finish	Raked	Smooth
Color	Ash	Clear Coat

DESIGN HIGHLIGHTS

Wood Balances Out Cool-Tone Modern Materials

The architect’s goal for the exterior was a “subtle, ‘low-contrast’ palette that allows the home to blend with its lush, wooded setting.” The neutral tone of the ranchwood Artisan Ash siding achieves this vision perfectly. The hemlock and cedar provide a natural counterpoint to other modern materials used on the exterior, like formed concrete and rusted metal accents, creating a sophisticated and balanced facade.

1×6 Tex-Gap Thermally Modified Hemlock Siding

The horizontal orientation of the 1×6 Tex-Gap siding dramatically emphasizes the home’s new, modern proportions, giving it a clean and contemporary profile. But the material is far from flat; the RW Artisan’s raked texture on the thermal hemlock catches the Pacific Northwest light beautifully throughout the day. This subtle variation adds a layer of quiet depth and visual interest that animates the entire exterior.

TO SPEC | Stainless Steel Fasteners

Will prevent fastener “weeping”, and ensures long-term strength and durability.

Exterior Gallery

Seamless Indoor-Outdoor CVG Cedar

A key feature of this renovation is the cohesive flow between the interior and exterior spaces. The design achieves this by using the same CVG Cedar with an AquaFir Clear Coat for both the interior ceilings and the expansive outdoor patio enclosure. This continuous use of material blurs the lines between inside and out, creating a seamless transition and a unified material experience that highlights the natural beauty of the cedar paneling.

Brightened Interior – Wood Paneled Ceilings Frame Skylights

Inside, the home is flooded with beautiful natural light from generous, strategically placed skylights. The design uses the CVG Cedar paneling to frame these skylights, a choice that pays off dramatically. The incoming light activates the wood, pulling out the rich, warm tones and natural depth of the cedar and enhancing the feeling of being connected to the outdoors.

INTERIOR GALLERY

THE RESULT

A Beautiful Material Update to Split-Level

The use of ranchwood Artisan Ash siding and AquaFir clear coat interior ceiling was essential in transforming this split-level with lasting performance. The Thermal Hemlock siding and Cedar soffit showcase natural wood tones that not only age gracefully but also fulfill the design vision of a home connected to its wooded environment, both inside and out.

This project demonstrates how thoughtful use of prefinished wood can elevate everyday architecture through quality materials, refined texture, and precise detailing.

Contact Us to Learn more about our ranchwood Artisan and AquaFir Product Lines

Thermally Modified Siding with Charred Cedar Soffit

PROJECT DETAILS

Location:
Coeur D’Alene, Idaho

Project Type:
Lakefront Residence

Architect:
d’Zign Group

Applications + Products

• Siding: Thermally Modified CVG | AquaFir | Charcoal | Wire Brushed | 1×8 Tex Gap
• Soffits: Western Red Cedar CVG | Charwood | Tiger | 1×6 Beveled T&G WP4
• Trim: Thermally Modified CVG | AquaFir | Charcoal | Wire Brushed | 1×3 & 1×4 Square Edge

THE VISION

A Bold Lakeside Statement: Harmonizing Modern Design with Natural Beauty

The vision for this striking lakefront residence was to create a bold, modern statement that honors its pristine setting. d’Zign Group aimed to design a home that captures the expansive views of Coeur D’Alene Lake while harmonizing with the surrounding evergreen forest. The goal was to achieve a seamless blend of rustic warmth and contemporary sophistication through the thoughtful use of natural materials and strong architectural lines.

THE SOLUTION

Premium Wood Products Deliver a Striking, Sustainable Design

Montana Timber Products provided a comprehensive wood solution that met both the aesthetic and performance requirements of this ambitious project. The use of thermally modified Clear Vertical Grain (CVG) AquaFir for siding and trim offered the perfect combination of beauty and resilience. The charred finish added a sophisticated, modern touch while enhancing the wood’s natural resistance to weathering and insects.

For the soffit, Clear Vertical Grain Western Red Cedar was selected, providing a complementary aesthetic and leveraging cedar’s inherent resistance to decay. The Charwood finish unified the soffit with the overall design scheme.

DESIGN CONSIDERATIONS

Coeur D’Alene Showcases Montana Timber Products’ Premium Materials

1. Climate Adaptation: The thermally modified Aquafir was chosen for its enhanced stability and moisture resistance, crucial for the lakefront setting.
2. Aesthetic Cohesion: The charred finish and wire-brushed texture create a captivating interplay of light and shadow, unifying the home’s exterior.
3. Sustainability: By using locally sourced, sustainably produced materials, the project aligns with environmental stewardship goals.

This Coeur D’Alene residence showcases how Montana Timber Products’ premium materials can elevate architectural design, creating a home that is not only visually stunning but also durable, sustainable, and perfectly attuned to its environment.

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Project Gallery

Natural Beauty Cladded in our Thermally Modified Wood

Reaching New Heights in Wellbeing-Centric Living, the Velvære community, nestled between Park City’s iconic Deer Valley Resort and North America’s newest ski destination, Mayflower Mountain Resort, redefines mountain living. Blending seamlessly with the breathtaking Utah landscape, the modern mountain townhomes at Velvære showcase our new thermally modified wood product offering.

PROJECT DETAILS

Location
Park City, UT

Project Type
Townhomes

Applications + Products

• Vertical Exterior Cladding:
  • 1″x4″ | AquaFir™ | clear coat | Shiplap with ¼” reveal | raked texture
  • 1″x6″ | AquaFir™ | clear coat | Shiplap with ¼” reveal | raked texture
• Horizontal Exterior Cladding
  • 1″x8″ | ranchwood™ | Western | Shiplap with ¼” reveal | raked texture

Species & Grade

Thermally Modified Hemlock (Clear Vertical Grain)

THE VISION

Harmonizing with Nature: The Vision for Velvære

The vision for the Velvære townhomes was to create a modern mountain living experience that seamlessly integrates with the surrounding natural beauty while embodying the community’s focus on wellbeing. Inspired by the principles of biophilic design, the architects sought to foster a deep connection between residents and nature. This approach emphasizes the use of natural materials, visual connections to the outdoors, and the creation of spaces that evoke a sense of tranquility and well-being. The choice of thermally modified Hemlock was central to this vision, not only for its inherent warmth and rich texture but also for its sustainable qualities. These luxury homes are designed for discerning individuals who appreciate both refined aesthetics, environmental consciousness, and a wellbeing-focused lifestyle, offering a luxurious yet responsible way to experience the unique charm of Park City and the immersive experiences of Velvære.

THE SOLUTION

Thermally Modified Durability Meets Refined Design

Our thermally modified Hemlock was the cornerstone of this project, offering a compelling combination of performance and aesthetics perfectly suited for the demanding mountain environment of Park City. The following benefits illustrate why it was the ideal choice:

Design Considerations

• Sustainability
• Longevity
• Aesthetic Cohesion

CONCLUSION

Building a Sustainable Legacy

The Velvære townhomes stand as a testament to the power of thoughtful design, sustainable materials, biophilic principles, and a commitment to wellbeing. By embracing the natural beauty and resilience of thermally modified wood, this project offers a modern mountain living experience that is both luxurious and environmentally responsible, creating a harmonious balance between sophisticated living, a deep connection to the natural world, and a truly enriching lifestyle.

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Project Gallery

A Modern Approach to Exterior Wood Cladding

Project Details

Location
Park City, UT

Project Type
Private Residence

Applications + Products

• Horizontal Siding: 1×6 AquaFir, Yukon color, Tex Gap Profile, Thermally Modified CVG Hemlock, smooth texture
• Soffits: 1×6 AquaFir, Honey Blonde color, T&G Profile, non-modified CVG Hemlock, smooth texture
  

THE VISION

Embracing Mountain Modern Elegance

The Park City residence showcases a mountain modern aesthetic, blending natural tones of prefinished thermally modified wood with limestone masonry to enhance its sophisticated appeal. Expansive windows and open spaces offer breathtaking views, seamlessly connecting the interior with the stunning mountain landscape. This design achieves a luxurious yet natural harmony that epitomizes contemporary mountain living.

THE SOLUTION

Thermally Modified Wood with Tex Gap Profile: A Perfect Pairing

Thermally modified wood undergoes a specialized heat treatment process, enhancing its natural properties:

• Increased Durability: Highly resistant to rot, decay, and moisture.
• Dimensional Stability: Minimizes warping, cupping, and other common wood movement issues.
• Hydrophobic Properties: Naturally repels water, reducing moisture-related problems.
• Sustainably Sourced: Harvested, treated, and milled to specification in North America.
• Chemical-Free: Achieves superior performance without harmful chemicals.

The Tex Gap profile complements these benefits by offering:

• Blind Fastening: Enables hidden nailing in the tongue, resulting in a clean, nail-head-free appearance.
• Enhanced Aesthetics: Provides a sleek, uninterrupted board look that elevates the overall design.
• Improved Durability: Prevents improper nail sinking, eliminating potential water ingress points.

Design Considerations

1. Contrasting Elements: Black corner trim and facia wrap contrast the thermally modified hemlock siding colored in Yukon Aquifer, creating a complementary mountain modern aesthetic.
2. Tex Gap Profile Installation: Meticulous installation techniques ensure the durability and longevity of Tex Gap profile siding to ensure lifetime durability.
3. Climate Resilience: Montana Timber Product’s thermally modified wood offers enhanced stability and moisture resistance, ideal for Park City Utah’s harsh mountain environments.
4. Finish Options: Various finish options for the AquaFir™ wood were explored to achieve the desired aesthetic while preserving the material’s natural properties, resulting in the selection of the Yukon color for siding and Honey Blonde for soffits, which complements the limestone masonry and enhances the home’s connection to its mountain setting.

This Park City residence achieves a perfect balance of form and function by combining thermally modified wood with the Tex Gap profile. The result is a visually striking exterior that offers superior protection against the elements, reduced maintenance requirements, and a sustainable building envelope that will stand the test of time in its mountain setting.

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