Thermal elements application

Page updated on: 08/08/2023

In April 2006 the government made major changes to a section of the Building Regulations concerned with energy conservation. These changes were designed to help combat climate change and reduce energy waste in buildings.

One of the changes was to introduce new requirements that would apply when a Thermal Element was to be renovated or replaced. A Thermal Element is a roof, wall or floor which separates a thermally conditioned (heated or cooled) space from any of the following:

  • The outside (including the ground)
  • An unheated part of the same building
  • A structure exempt from the building regulations, such as porch or conservatory, or  Part of the same building heated or cooled to a different temperature

Renovation of a Thermal Element means adding a new layer to a Thermal Element or the replacement of an existing layer. When the renovation is more than 50% of the surface of the individual element or 25% of the total of the building envelope, Building Regulations approval will be required prior to carrying out the work and the Thermal Element may require upgrading to provide more insulation.

When assessing this area proportion it should be taken as that of the individual element, not all the elements of that type of building. The area of the element should be interpreted in the context of whether the element is being renovated from inside or outside, e.g. if removing all the plaster finish from the inside of a solid brick wall, the area of the element is the area of external wall in the room. If removing external render, it is the area of the elevation in which that wall sits.

The consequence of this change is that much building work, previously exempt from the Building Regulations as it was considered a repair, may now require approval. For example:

  • Replacement of a slate or tiled roof covering even if like for like  
  • Re-plastering of a wall
  • Replacement of felt on a flat roof
  • Renewal of a ceiling below a cold loft space
  • External rendering or re-rendering of a wall
  • Renewal of cladding to a dormer
  • Renovation of a ground floor involving replacement of screed or timber decking

It is a contravention of the Building Regulations not to submit an application for building work such as indicated above. This could lead to a prosecution and a fine for the person carrying out the work, and may cause problems if the property is subsequently sold. For non-domestic buildings please use the Full Plans application form.

Download thermal elements application   Apply for full plans