Planning retrofit measures, Retrofit technical considerations

Third Party Guarantees with Solid Wall Insulation Guarantee Agency (SWIGA)

Introduction

Third party guarantees are a form of securing loans, where the guarantor is liable for the outstanding debt including interest in case the borrower defaults. An example of this is the Trustmark guarantee, which is a financial protection mechanism provided by Trustmark registered businesses for home improvements, covering workmanship and materials.

Published: 24 April 2026


The purpose of this toolkit is to provide a clear and practical overview of how quality is assured for retrofit projects through the use of a third party guarantee. It highlights what needs to happen at each stage, from prenotification through to installation and handover. The use of guarantees can help to prevent non-compliance and reduce risk.

This toolkit should aid stakeholders understanding of:

Why early engagement with the guarantee (GT) provider matters.

What “good practice” looks like in real delivery.

Where common risks arise and how they can be avoided.

Download the PDF below to access this Toolkit. 

Readers that would like this document in a more accessible format should contact rise@turntown.co.uk.