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Thermowood Mass Loss CalculatorThermal Modification Mass Loss and Class

Calculate the mass loss that occurs during thermal modification (Thermowood) and predict the resulting durability class, equilibrium moisture reduction and dimensional stability improvement.

ThermoD / ThermoS ClassMass Loss %EMC ReductionDurability GainPDF Report
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Thermowood Mass Loss Calculator

Thermal Modification Mass Loss and Class

Modification Process

Base species before modification.

deg C

ThermoS ~190C, ThermoD ~212C+.

hours

Peak temperature hold time.

Sample Details
kg

Oven-dry mass before treatment.

OK
Thermal Modification Results
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%
Mass Loss
-
class
Thermowood Class
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% EMC
Reduced EMC
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class
Durability Class
PropertyBeforeAfter TreatmentChange
Mass Loss Calculation
About Thermowood Mass Loss Calculator
Thermal modification (the Thermowood process) heats wood to 160-240 C in a low-oxygen environment, permanently altering its chemistry. The wood loses mass as hemicelluloses break down - and this mass loss is the single best predictor of the improvements gained: lower equilibrium moisture, better dimensional stability, and higher decay resistance. This tool estimates mass loss and the resulting performance class.
Where Is This Used?
Thermowood ProductionDecking + CladdingModified Wood QCProcess OptimizationDurability CertificationExport Specification
Formulas Used
Mass loss % ~ f(temperature, duration, wood type)ML = base(T) x duration_factor x type_factorThermoS class: ~180-200 C, mass loss 3-7%ThermoD class: ~210-230 C, mass loss 7-15%EMC reduction ~ proportional to mass loss (up to ~50% lower)Durability improves from class 4-5 toward class 1-2 (EN 350)
Frequently Asked Questions
Why is mass loss the key quality indicator?
Mass loss directly measures how much hemicellulose has been degraded - the chemical change responsible for all Thermowood benefits. Producers target a specific mass loss (e.g. 8-10% for ThermoD) because it reliably predicts the final EMC, stability and decay resistance, regardless of small process variations.
What is the difference between ThermoS and ThermoD?
ThermoS (Stability) is treated around 190C for improved dimensional stability and is used for indoor and shaded outdoor applications. ThermoD (Durability) is treated hotter (~212C+) for higher decay resistance and is used for exterior cladding and decking. Higher temperature means more mass loss and darker color.
Does thermal modification reduce strength?
Yes - the trade-off for stability and durability is reduced strength, especially impact bending and tension. Mass loss above ~12% can make wood brittle. This is why ThermoD decking is not used structurally, and why controlling mass loss precisely matters - you want maximum durability with acceptable strength.
ResourcesView the formulasFormula Library
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