Equilibrium moisture content EMC
Technical paper 35: Moisture measurement in the historic environment, published by Historic Environment Scotland in 2021, defines equilibrium moisture content as: ‘The moisture content at which a material is neither gaining nor losing moisture through exchanges with the ambient environment.’
Equilibrium Moisture Content (EMC) refers to the specific state of a hygroscopic material in relation to its moisture content, and relative to its surrounding environment. It is the point at which the material is neither gaining nor losing moisture and remains in balance or equilibrium with its local environment. The value of the EMC depends on the material being described, as well as the relative humidity and the temperature of its surrounding environment or the air within which it is in contact.
For example, wood is a hygroscopic material, so its moisture levels can rise and fall relative to its local environment. In timber the EMC is most likely to be lower than its Fibre Saturation Point (FSP) which is generally around hen 30%. The exact EMC figure will vary depending on a number of variables which include the type and age of the wood, the area in the cross section of timber and the moisture and temperature of the local environment. For more information see: Fibre saturation point.
This characteristic of hygroscopic materials to help balance moisture and temperature levels can be beneficial to internal environments when left exposed internally.
[edit] Related articles on Designing Buildings
Featured articles and news
A change to adoptive architecture
Effects of global weather warming on architectural detailing, material choice and human interaction.
How big is the problem and what can we do to mitigate the effects?
Overheating guidance and tools for building designers
A number of cool guides to help with the heat.
The UK's Modern Industrial Strategy: A 10 year plan
Previous consultation criticism, current key elements and general support with some persisting reservations.
Building Safety Regulator reforms
New roles, new staff and a new fast track service pave the way for a single construction regulator.
Architectural Technologist CPDs and Communications
CIAT CPD… and how you can do it!
Cooling centres and cool spaces
Managing extreme heat in cities by directing the public to places for heat stress relief and water sources.
Winter gardens: A brief history and warm variations
Extending the season with glass in different forms and terms.
Restoring Great Yarmouth's Winter Gardens
Transforming one of the least sustainable constructions imaginable.
Construction Skills Mission Board launch sector drive
Newly formed government and industry collaboration set strategy for recruiting an additional 100,000 construction workers a year.
New Architects Code comes into effect in September 2025
ARB Architects Code of Conduct and Practice available with ongoing consultation regarding guidance.
Welsh Skills Body (Medr) launches ambitious plan
The new skills body brings together funding and regulation of tertiary education and research for the devolved nation.
Paul Gandy FCIOB announced as next CIOB President
Former Tilbury Douglas CEO takes helm.
UK Infrastructure: A 10 Year Strategy. In brief with reactions
With the National Infrastructure and Service Transformation Authority (NISTA).
Ebenezer Howard: inventor of the garden city. Book review.
Airtightness Topic Guide BSRIA TG 27/2025
Explaining the basics of airtightness, what it is, why it's important, when it's required and how it's carried out.