Material Definitions

Capillary action: The movement of water through the pores of a material due to surface tension, affecting its hygrothermal performance.

Combustibility: The measure of how easily a material can ignite and sustain combustion.

Conductivity (thermal): The ability of a material to conduct heat, often measured in watts per meter-kelvin (W/m·K). Typical values range from 0.02 W/m·K for insulating materials to over 400 W/m·K for metals like copper.

Embodied carbon: The total greenhouse gas emissions associated with the extraction, production, transportation, and disposal of a building material, expressed in units of CO2 equivalent per unit mass or volume.

Emissivity (thermal): The effectiveness of a material's surface in emitting energy as thermal radiation. Values range from 0 (no emission) to 1 (perfect emitter).

Fire performance: A general term that encompasses various fire-related properties, such as fire resistance, flame spread, and smoke development.

Fire propagation index: A measure of the contribution of a material's surface to the growth of fire, taking into account both flame spread and heat release.

Fire resistance: The ability of a material or assembly to maintain its structural integrity and/or insulating properties when exposed to fire for a specified period.

Flame spread index (FSI): A rating that quantifies the surface burning characteristics of a material, with lower values indicating slower flame spread. Values typically range from 0 to 200, with lower values indicating better performance.

Hygroscopicity: The ability of a material to absorb moisture from the surrounding environment, influencing its hygrothermal behavior.

Impact insulation class (IIC): A rating that measures the effectiveness of a material or assembly in reducing impact sound transmission, such as footfall noise. Higher values indicate better performance, typically ranging from 25 to 60 or higher.

Moisture content: The amount of water present in a material, which can affect its thermal and hygrothermal properties.

Noise reduction coefficient (NRC): A scalar representation of a material's sound absorption properties, ranging from 0 (perfectly reflective) to 1 (perfectly absorptive).

Reflectance (solar): The proportion of incident solar radiation that is reflected by a material's surface, affecting its thermal performance.

Smoke developed index (SDI): A rating that quantifies the amount of smoke generated by a material during combustion, with lower values indicating less smoke production. Values typically range from 0 to 450 or higher, with lower values indicating better performance.

Solar heat gain coefficient (SHGC): The fraction of incident solar radiation that is transmitted through a material as heat, affecting the energy performance of buildings. Values range from 0 (no transmission) to 1 (all incident radiation transmitted).

Sound absorption: The ability of a material to absorb sound energy, reducing noise levels and improving acoustics within a space.

Sound transmission class (STC): A rating that measures the effectiveness of a material or assembly in reducing airborne sound transmission. Higher values indicate better performance, typically ranging from 25 to 60 or higher.

Specific heat capacity: The amount of heat required to change the temperature of a unit mass of a material by one degree Celsius, typically measured in joules per kilogram-kelvin (J/kg·K). Values range widely depending on the material, from about 400 J/kg·K for metals to over 2000 J/kg·K for some insulating materials.

Thermal diffusivity: The rate at which heat is conducted through a material relative to its heat capacity, calculated as the ratio of thermal conductivity to the product of density and specific heat capacity.

Thermal expansion: The increase in a material's size due to temperature changes, often characterized by the coefficient of linear expansion, which is typically expressed in units of strain per degree Celsius (1/°C). Values vary widely depending on the material, from near zero for some ceramics to over 20x10^-6 1/°C for metals like aluminum.

Thermal mass: The ability of a material to absorb and store heat energy, which can help moderate indoor temperature fluctuations. Materials with high specific heat capacity and density, such as concrete and brick, typically have good thermal mass.

Thermal resistance (R-value): The measure of a material's resistance to heat flow, with higher values indicating better insulating properties. R-value is typically expressed in square meter-kelvin per watt (m²·K/W) and varies depending on the material and its thickness. Insulating materials can have R-values in the range of 1-10 m²·K/W or higher.

Water vapor permeability: The ability of a material to allow the passage of water vapor, which influences the hygrothermal performance of building envelopes. It is typically expressed in nanograms per Pascal-second-meter (ng/Pa·s·m), with values ranging from less than 1 for vapor barriers to over 1000 for highly permeable materials like wood.

These definitions, including typical values, should give you a better understanding of various material properties relevant to building construction and performance. Remember that the actual significance of each property may vary depending on the specific material and its application in a building project.