Hygrothermal Material Data

Understanding the hygrothermal properties of materials is essential for designing energy-efficient, durable, and comfortable buildings. Hygrothermal data encompasses various parameters such as bulk density, thermal conductivity, and water absorption coefficient, among others. See below for all Basic Material Data and Material Functions required for a HAMT simulation.

These properties dictate how materials interact with moisture and heat, influencing their performance and longevity in different environmental conditions.

Accurate characterisation of hygrothermal properties aids architects, engineers, and building professionals in selecting appropriate materials, designing effective building envelopes, and optimizing energy usage. However, they can be difficult to obtain as they are often not required to be tested for in local or International building codes.

Speckel identifies two types of hygrothermal materials groups. Where a product is Generic, we adopt hygrothermal defaults for Inputs and Functions based on local market conditions. Where a Supplier provides a material, we map the specific hygrothermal material data to their products.

Hydrothermal Material Properties in Speckel

Basic Material Data

Bulk Density

Mass per unit volume of a substance, usually expressed in kilograms per cubic meter (kg/m³). Typically ranges from 800 kg/m³ to 2400 kg/m³ depending on the material.


Fraction of the total volume of voids (pores) in a material, typically measured as a ratio. Generally ranges from 0.1 to 0.99 m³/m³.

Specific Heat Capacity, Dry

Amount of heat required to raise the temperature of a unit mass of a substance by one degree Celsius, when the material is dry. Commonly falls between 500 J/(kg K) to 1800 J/(kg K) for various substances.

Thermal Conductivity, Dry

Measure of a material's ability to conduct heat, typically at a specific temperature. Typically varies from 0.02 W/(m K) to 2.4 W/(m K) for different materials.

Water Vapour Diffusion Resistance Factor

Indicates a material's resistance to water vapor diffusion. Values range from 1 to 10000 or more, indicating varying levels of resistance to water vapor diffusion.

Reference Water Content

Amount of water present in a material under reference conditions. Usually ranges from 50 kg/m³ to 100 kg/m³ depending on the material and conditions.

Free Water Saturation

Saturation level of free water in a material. Typically varies from 0 kg/m³ (fully dry) to the bulk density value.

Water Absorption Coefficient

Rate at which a material absorbs water. Ranges from very low values kg/(m² s^0.5) for impermeable materials to higher values for more absorbent substances.

Moisture-dep. Thermal Cond. Supplement

Generally varies from 0 to 20% per percentage point change in moisture content.

Typical Built-In Moisture

Usually ranges from 50 kg/m³ to 200 kg/m³, depending on the material and manufacturing process.

Temp-dep. Thermal Cond. Supplement

Typically ranges from 0 to 0.001 W/(m K²), indicating the sensitivity of thermal conductivity to temperature changes.

Thermal Conductivity, Design Value

The anticipated thermal conductivity value for design purposes, typically not provided in your data.

Material Functions

Some hygrothermal functions describe properties that are not universally present in all materials. For instance, liquid transport coefficients are vital for accurately depicting transport processes in capillary-active materials like bricks but are nonexistent in non-capillary materials such as mineral wool.

Additionally, other hygrothermal functions offer refinements of basic material data, incorporating moisture or temperature dependencies, if applicable. Whether these refinements are beneficial or essential depends on the specific circumstances.

Hygrothermal functions typically involve multiple numerical values and are thus organised into tables. However, acquiring detailed tabular data can be labor-intensive, costly or non-existent. Consequently, Speckel offers functions capable of interpolating a complete table from two given entries or generating a table from related parameters, which are often more readily determined.

Moisture Storage Function

Moisture Storage Function provides insight into how materials retain moisture over time. It's essential for understanding the long-term behavior of materials in response to moisture exposure, allowing for informed decisions regarding moisture management strategies in building design and construction.

Liquid Transport Coefficient

A Liquid Transport Coefficient quantifies the rate at which liquids, such as water, move through materials. It's a critical parameter for assessing moisture ingress and distribution within building components, guiding the selection of appropriate materials and detailing to minimise the potential for moisture-related issues like water infiltration, mold growth, and structural damage.

Liquid Transport Coefficient - Suction

Suction refers to the ability of materials to draw in moisture from their surroundings. It plays a significant role in determining how materials interact with moisture, influencing their moisture content and susceptibility to damage.

Liquid Transport Coefficient - Redistribution

Redistribution describes the movement of moisture within materials, typically occurring due to variations in moisture content or environmental conditions. This phenomenon can lead to moisture migration within building components, affecting their structural stability, thermal performance, and durability.

Thermal Conductivity, moisture-dependent

This parameter reflects how a material's thermal conductivity changes with fluctuations in moisture levels. It's crucial for understanding the dynamic thermal behavior of materials in response to moisture exposure, influencing their insulating properties and thermal performance.

Water Vapor Diffusion Resistance Factor, moisture-dependent

This factor indicates how a material's resistance to water vapor diffusion adjusts with changes in moisture content. It's instrumental in assessing a material's ability to manage moisture ingress and egress, preventing moisture-related issues such as condensation, mold growth, and degradation.

Thermal Conductivity, temperature-dependent

This parameter represents how a material's thermal conductivity varies with fluctuations in temperature. It's essential for predicting the thermal behavior of materials under different environmental conditions, influencing their thermal performance and energy efficiency.

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