Perplexed by all this talk of u-values and blower door tests? Our sustainable building glossary will help you get to grips with the key terminology.

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Term Definition
Seasonal performance factor

The ratio of useful heat energy output from a heat pump to the electrical energy input (including compressor, circulation pumps and electrical immersion, if present) averaged over an entire heating season

single leaf

A single leaf wall consists of just one layer of a building material. Single-leaf walls of hollow concrete blocks were the most common form of construction in the greater Dublin area for decades. They are different to the cavity wall construction common throughout the rest of the country, which consist of two layers of masonry with a cavity in between.

solar gain

This refers to the heat and light energy that a building receives passively from the sun. Designing a building so that the rooms that are used most during the day face south means they will get light and heat from the sun, reducing the need for mechanical heating systems and electrical lighting

Space heating demand

The amount of active heating input required to heat a building usually expressed in kWh/m2/yr. It is often calculated using building energy software applications such as PHPP, Deap or Sap

Strip foundation

A strip of concrete running under all of a building's load bearing walls. This will normally include the external walls, and possibly some of the internal walls.

Surface to volume ratio

This is the total external surface area of a building relative to its volume. A lower surface to volume ratio is generally more energy efficient, as it means there is less surface area from which heat can escape the building.