Tooltip Tags: ventilation

Dew point

Dew point is the temperature below which the equilibrium between evaporation and condensation is tilted towards condensation, i.e. condensation starts to form.

Dew point is also a proxy the vapour pressure. Comparing the dew point of one area to another makes it possible to see where vapour is being generated or conversely removed (normally through ventilation).

Relative humidity

Relative humidity is defined as the measure of how much vapour is in the air compared to air’s capacity to hold vapour – expressed as a percentage.

It is a function of vapour pressure (quality of vapour) and temperature. As temperature rises, air can hold more vapour.

Conversely as temperature drops, air holds less vapour until it meets the dew point at 100%RH, when dew or condensation forms.

TIP: datalogger

Datalogger. Monitor humidity and temperature against wall or ceiling, to see effects of improvements, such as ORIA Wireless Thermometer Hygrometer (20m (2 Packs))

TIP: kitchen extractor fan

Kitchen extractor fan. Consider instructing general builder to duct out kitchen extractor fan – using rigid ducting. Hoover HGM600X (£149) has a Which! Best buy.

TIP: trickle vents

Trickle vents. Consider instructing general builder to install trickle vents (approx. £30 each), see