Energy Companies Obligation (ECO): Supplementary guidance on hard-to-treat cavity wall insulation

Publication date
22nd May 2014
Information types
Policy areas

This document provides supplementary guidance in relation to specific categories of hard-to-treat cavity wall insulation under the Energy Companies Obligation (ECO) and should be read in conjunction with the ECO Guidance for Suppliers.

On 27 August 2013 we published a consultation document seeking views on our proposed requirements under ECO for demonstrating the characteristics of a hard-to-treat cavity wall (HTTC) to which insulation has been installed.
The consultation put forward proposals to address concerns that a significant number of HTTC measures installed under ECO may have been installed to cavity walls that do not meet the statutory definition of ‘hard to treat cavity’. The consultation closed at 1pm on 24 September 2013. A high number of responses were received. The key points raised by those responses and the changes made to our proposals as a result are detailed in the summary of responses to consultation document.

Additional requirements for demonstrating the characteristics of hard-to-treat cavity walls

The main requirements introduced by this supplementary guidance are outlined below.

Narrow cavities

A Narrow HTTC Declaration (Appendix 1, or an approved equivalent) must be completed for all narrow HTTCs.  The declaration must show that:

  • The cavity width has been measured in accordance with the methodology in Chapter 2; and
  • The measurement of the cavity width and the completion of the declaration has been conducted in accordance with one of the options in Chapter 2.

Chartered surveyor report for HTTCs

All HTTC measures notified to Ofgem as remedial works, non-standard materials or techniques, or uneven stone, must be identified as such in a report by a chartered surveyor, using the template provided in Appendix 2 or an approved equivalent.

Chartered surveyor reports must be completed either through a site visit or through a desk-based exercise using a robust body of evidence. In a minimum of 20 percent of cases the report should be based on a site visit undertaken by the chartered surveyor.

Technical Monitoring

This requirement relates to those installations completed between 1 January 2014 and 30 September 2014. For further details, see the ‘Update to Supplementary Guidance on Hard-to-Treat Cavity Wall Insulation’ document available below.

An additional 5 percent technical monitoring will apply to the following categories of HTTCs:

• narrow cavities;
• cavities requiring substantial remedial works;
• cavities requiring non-standard materials or techniques.

This technical monitoring should be conducted at the pre-installation or mid-installation stage. As an exception, for narrow cavities only, suppliers may choose to conduct a proportion of the additional technical monitoring at post-installation stage; this must include measurement of the cavity width.

Date of effect

The requirements in this document take effect for installations completed from 1 January 2014, unless stated otherwise.