Water vapour in the built environment
Water vapour is the phase of water (H2O) that takes the form of a gas. It is a component of the Earth’s hydrologic cycle and is abundant in the atmosphere.
Boiling liquid water can produce water vapour by a process of evaporation, while ice can produce water vapour via sublimation. The use of water vapour in the form of steam has been a fundamental part of energy production since the Industrial Revolution.
Air will generally include moisture in the form of water vapour. Absolute humidity is the mass of water vapour in a volume of air divided by the mass of dry air. When air cools, it is less able to 'hold' moisture, that is, the saturation water vapour density falls, and so the relative humidity rises. When the relative humidity reaches 100%, the air will be saturated. This is described as the dew point. If the air continues to cool, moisture will begin to condense.
For more information see: Humidity.
The presence of water vapour in a building can lead to problems with condensation and moisture which can result in mould growth, damp, staining, and so on.
Moisture in buildings can be reduced by removing or reducing the source of water (such as washing processes, leaking pipes, rising damp and so on) or by drainage, ventilation, increasing temperatures or dehumidification.
[edit] Related articles on Designing Buildings
Featured articles and news
Shortage of high-quality data threatening the AI boom
And other fundamental issues highlighted by the Open Data Institute.
Data centres top the list of growth opportunities
In robust, yet heterogenous world BACS market.
Increased funding for BSR announced
Within plans for next generation of new towns.
New Towns Taskforce interim policy statement
With initial reactions to the 6 month policy update.
Heritage, industry and slavery
Interpretation must tell the story accurately.
PM announces Building safety and fire move to MHCLG
Following recommendations of the Grenfell Inquiry report.
Conserving the ruins of a great Elizabethan country house.
BSRIA European air conditioning market update 2024
Highs, lows and discrepancy rates in the annual demand.
50 years celebrating the ECA Apprenticeship Awards
As SMEs say the 10 years of the Apprenticeship Levy has failed them.
Nominations sought for CIOB awards
Celebrating construction excellence in Ireland and Northern Ireland.
EPC consultation in context: NCM, SAP, SBEM and HEM
One week to respond to the consultation on reforms to the Energy Performance of Buildings framework.
CIAT Celebrates 60 years of Architectural Technology
Find out more #CIAT60 social media takeover.
The BPF urges Chancellor for additional BSR resources
To remove barriers and bottlenecks which delay projects.
Flexibility over requirements to boost apprentice numbers
English, maths and minimumun duration requirements reduced for a 10,000 gain.
A long term view on European heating markets
BSRIA HVAC 2032 Study.
Humidity resilience strategies for home design
Frequency of extreme humidity events is increasing.
National Apprenticeship Week 2025
Skills for life : 10-16 February