- Project plans
- Project activities
- Legislation and standards
- Industry context
- Specialist wikis
Last edited 28 Sep 2020
Thermal admittance of building materials
Thermal admittance (Y) is a measure a material's ability to absorb heat from, and release it to, a space over time. This can be used as an indicator of the thermal storage capacity (thermal mass) of a material, absorbing heat from and releasing it to a space through cyclical temperature variations, thus evening out temperature variations and so reducing the demand on building services systems.
Typical admittance values based on a 24-hour cycle might range from 1.0 for a timber frame wall with brick outer leaf, to 2.65 for a cavity wall with 100 mm dense aggregate block (ref. The Concrete Centre).
The admittance time lead, ω (expressed in hours), is a measure of the time delay between the peak heat flow between the material surface and the space and the time of the peak temperature in the space.
As the thickness of a material increases, so the admittance approaches a constant value. It is generally considered that in the UK, with a 24-hour thermal cycle, heat energy can only penetrate up to 100 mm into materials such as concrete and masonry.
 Related articles on Designing Buildings Wiki
 External references.
- ISO 13786:2007. Thermal performance of building components -- Dynamic thermal characteristics -- Calculation methods.
- The Concrete Centre: Thermal Mass Explained (2012 update).
Featured articles and news
A new gallery for the University of Huddersfield.
What will it take to stop it ?
To celebrate world bee day 2022 !
Not forgetting part F and the new part overheating part O.
As energy prices jump up in cost.
With people in the UK from Ukraine.
Industry leader Steve Murray takes on role.
An abundant and versatile building material.
600,000 heat pump installations targeted per year by 2028.
Helping prevent those unwanted outcomes.
How has transport changed due to Covid-19 ?
Will you need it ? after June 15 and the new Part O ?
Create an account and write the first of many articles.
CIAT commentary after the first meeting.
Who is to blame?
Research recommends focussing on portfolio success rather than project success.
The revised standard for mapping underground utilities.