This guide serves to both define and explain the range of material properties that are used within this site and the web applications it provides. The aim is to establish a common reference so that important points and concepts do not need to be continually reiterated in multiple locations, but can be made within the property definition that they pertain most to.

Material properties come in two main types, those that describe the behaviour of a material or element when things impact upon or pass through it, and those describing any emissions from a material or element out into surrounding spaces. This guide considers both.

Property Types

In this guide only material instance properties are listed. These are basically the ones whose name ends with ‘ance’ as opposed to ‘ivity’. Whilst not entirely universal, the convention is that terms such as resistivity, transmissivity, conductivity, reflectivity and absorptivity all refer to properties of a particular type of material and are given as values per unit of thickness or size. On the other hand, terms such as resistance, transmittance, conductance, reflectance and absorptance all refer to actual measured or calculated values from a specific instance or sample of a material which has a known thickness or size. Thus, if you know either value and the thickness or size of your test material, then you can easily derive the other value.

Where appropriate, material type version of those properties, which end in ‘ivity’ are discussed within the corresponding ‘ance’ definintion.

Behavioural Properties

The behaviour of a material or building element describes what happens when things like air, heat, light, moisture vapour or sound impact upon its surfaces or pass over, through or around it.

Air Flow

Properties affecting the flow of air over, through or around a material or aperture.

Heat Flow

Properties affecting the flow of heat through a material or aperture.

Light Properties

Properties affecting how light reflects, is absorbed or passes through a material or aperture.

Moisture Vapour

Properties affecting the flow of moisture vapour through a material or aperture.

Solar Radiation

Properties affecting how solar radiation reflects, is absorbed or passes through a material or aperture.

Sound Propagation

Properties affecting how sound reflects, is absorbed or passes through a material or aperture.

Visual Properties

Properties affecting the visual presentation of a material.

Emission Properties

Emissions refer to any heat, light, sound or off-gassing that occurs from a material or building element. These properties are usually applied to elements such as appliances, mechanical equipment, lights, speakers and even people who occupy the building.

Gaseous Emissions

Metrics for quantifying off-gassing from materials, appliances or equipment.

Heat Emissions

The different types of heat output by appliances or equipment.

Light and Radiation

Metrics for the amount of light output or radiant emissions by lamps, luminaires, appliances or equipment.

Sound Emissions

Metrics for the amount of sound emitted by appliances, equipment or speakers.