Many terms in the construction industry can be confusing for outsiders, so we have pulled together a building industry glossary. We have attempted to explain some of the most common acronyms and sector-based phrases here. If there are any other words you think we should cover, please get in touch and let us know.

Building Industry

When we talk about the building industry, we are referring to both the construction sector focused on new developments, and the maintenance, repair, and retrofit of existing properties.


A U-Value is the measure of heat transfer through an object or structure. U-Values are generally used to define thermal performance (heat loss) and assess the performance of a building.

Thermal Bridging

A thermal bridge – also called a cold bridge, heat bridge or thermal bypass – is an area of a buildings construction that has a significantly higher heat transfer than its surrounding materials. Thermal bridging can be responsible for up to 30% of a dwelling’s heat loss (BRE).


A thermogram, otherwise known as a thermal image, is a graphic or visual record produced from a thermal imaging camera.

Solar Gain

Also known as ‘solar heat gain’ or ‘passive solar gain’, solar gain is the increase in thermal energy of an object, structure or space as it absorbs solar radiation (heat from the sun).


All materials absorb, reflect and emit radiant energy – emissivity is the measurement of how well the surface of a particular material emits heat in the form of infrared energy. We use known emissivity values to adjust our thermal cameras for specific building materials, allowing for more accurate readings.

R.A.T. (Reflected Apparent Temperature)

Reflected Apparent Temperature is the average temperature of all background infrared radiation in a scene. Once calculated, this value is used to compensate for any significant heat sources – allowing for more accurate temperature measurements.


Infrared radiation (IR) is a type of radiant energy that’s invisible to the human eye but can be felt as heat. Any object with a temperature above absolute zero (-273.15ºC) emits infrared radiation. The higher the temperature of an object, the greater the intensity of infrared radiation.

T.I. (Thermal Index)

Thermal Indexing is a formula used to calculate the thermal performance of an area. It’s used to quantify subjective images by accounting for air and surface temperatures during a survey. A Thermal Index value of 0.75 is the recommended lowest value that should be achieved within a building to negate the possibility of condensation and mould.