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

Using sunlight for indoor lighting needs


See Dwelling Energy Assement Procedure (Deap)

Demand controlled ventilation

Demand controlled ventilation is a control strategy that modulates ventilation rates based on demand. While typically associated with mechanical extract ventilation, it can be applied in other applications too, notably including passive stack ventilation and mechanical ventilation with heat recovery. As such there is some discussion over whether demand controlled ventilation should be referred to as a ventilation system, or a control approach for various ventilation systems.

Typically DCV systems modulate ventilation rates based on relative humidity levels, though it is also possible to utilise sensors to track other pollutants, such as CO2.

While ventilation systems should be principally thought of in terms of indoor air quality rather than energy performance, it's estimated that a typical demand controlled mechanical extract ventilation system (DCMEV) would reduce ventilation heat loss by approximately 50% compared to an MEV system with no demand control.  

Synonyms - Demand control ventilation, DCV, demand-controlled ventilation
Dew point

The temperature below which water vapour in the air will start condensing to liquid. This is important in buildings, because anywhere there is a dew point, there is a risk of condensation and mold growth. For example, improperly installing insulation on the inside of a wall can create a dew point between the insulation and the wall.

District heating

A type of heating system in which heat is piped from a large central heating system (such as a boiler) to multiple units (such as houses or apartments), rather than each unit having its own separate heat source. Often financed via energy service companies (ESCos), district heating systems tend not to become less viable in very energy efficient buildings, given that the low space heating demand means smaller bills payable to the ESCos

dry lining
Dwelling Energy Assement Procedure (Deap)

A software programme used to calculate the Building Energy Rating (BERs) of buildings