Solar transmittance through building fabric (gtot)
Solar heat gain in buildings can be beneficial in the winter, as it reduces the need for heating, but in the summer it can cause overheating.
The total solar heat transmittance into a space is the sum of the solar heat that is transmitted directly through its fabric (such as solar radiation transmitting through glass), and the solar heat that is absorbed by its fabric and then re-emitted into the enclosed space.
Total solar energy transmittance (gtot) relates to the performance of solar protection devices such as blinds and shutters and is the percentage of solar energy incident on the fabric of a blind or shutter that is transmitted to the interior of the building, including both the transmittance of the solar protection device itself and of the glazing.
According to the EN 14501 standard (Blinds and Shutters, Thermal and Visual Comfort, Performance Characteristics and Classification), it is measured on an index of 0 to 1. The closer the fabric’s index is to 0, the more efficient it is at protecting against heat and reducing solar energy; whereas an index of 1 means that all the incident solar radiation is transmitted.
Two methods are used for calculating the gtot of a solar protection device:
- Simplified calculation method: EN ISO 52022-1 (replacing EN 13363-1)
- Detailed calculation method: EN ISO 52022-3 (replacing EN 13363-2)
[edit] Find out more
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
Not buildings. Happy holiday from DB.
Future Homes Standard: Industry calls for more ambition
As the Government FHS consultation finally closes.
Improving government projects with data and AI
Enabling better outcomes, efficient modern delivery and influential leadership on government projects.
BSRIA Living Laboratory Innovation Challenge
Final days for submission, closing March 29.
Windows, their frames, forms, factors and functions.
The hidden subtleties of U-Value calculations
Different contexts and what to include as variables.
A brief run down with related articles.
Electrical sector calls for safer public EV charge points
Serious concerns about electrical safety in the public domain.
Building Blocks manifesto presented to parliament
Architects Declare call in for support of five critical policies.
The four elements of project management with APM
Analysis, expectations, collaborative communication and partnerships.
City of London launches Heritage Building Retrofit Toolkit
Empowering owners to initiate necessary adaptations.
Guidance on RAAC in listed buildings
Published by Purcell, endorsed by IHBC, SPAB and C20.
Learning from the past.
Reluctance to hire people with criminal convictions revealed
Employing People with Criminal Convictions Report.
Tackling unconscious bias; Women's History Month
Personal reflections, as the last week of March approaches.