Vapour Permeability
Vapour permeability, or "Breathability" in a building refers to the ease with which water vapour passes through building elements. Building elements where vapour permeability is poorly designed can result in condensation, leading to unhealthy living environments and degradation of fabric.
Vapour permeability can be expressed in several ways:
- vapour resistivity of a material, measured in GNs/kgm (giga Newton seconds per kilogram metre) or MNs/gm (mega Newton seconds per gram metre)
- vapour resistance for a given thickness of material, in GNs/kg or MNs/g
- vapour resistance factor, also known as th µ-value, which is the resistivity of a material relative to that of still air. It is a factor, and has no units.
- "perms", short for permeability, used commonly in North America, measured in grains/(ft2 ·h·inHg)
[edit] Related articles on Designing Buildings Wiki
Featured articles
Check out some of the best features and news from Designing Buildings as well as key stories from around the web.
Historic England publishes research into embodied carbon when retrofitting traditional buildings.
New Prime Minister delivers on ECA call for cut in electricity costs.
CIOB reacts to the announcement of Andy Burnham as Prime Minister.
Heritage and conservation science workforce survey - Have your say.
England's Suburbs 1820-2020. Book review.
New, more proportionate and targeted approach for higher-risk building assessments.
Government brings British Steel into public ownership.
UKCW Birmingham returns with bold new theme and focus.
New guidance published on competence requirements for self-certification schemes.
Construction Management, 8 July
NEETs crisis drives interest in trades, but apprenticeships barriers remain.
Passive fire protection webinar
MEP services penetration seals.
Where its at podcast (and video) - The role of the Architectural Technologist as an Expert Witness.