The badly fitted installation has left homes badly damaged. ITV News Wales reporter Rhys Williams investigates.
Insulating homes is key to the green energy policies of governments across the UK.
Most recently, the UK government announced £6 billion of funding to insulate houses. The Welsh government also offers funding for low-income households to help with energy efficiency through a scheme called Nest, previously called Arbed.
But what happens when this vital work is bungled? The residents of Caerau, in the Llynfi Valley near Bridgend, know only too well.
In 2012, the installation of external insulation on 25 properties in the village was contracted by Bridgend council using funds from the Arbed Scheme, with a further 79 funded through the UK government's Community Energy Saving Programme (CESP).
This type of insulation is applied to the outside of a property and can lead to big energy savings, but when it’s not installed correctly or isn’t right for the property, it can cause serious damp problems.
Within months, residents reported serious problems with damp. The contract for the work was awarded by Bridgend council to a company which was run by one of its cabinet members, and councillor for Caerau, Phil White.
The company no longer exists and Mr White died last year.
An internal audit report by Bridgend council recently found "a number of significant concerns" with the scheme, with no procurement process followed and "no due diligence checks” carried out.
It’s not unique to Caerau, with some estimates that up to two million homes may have problems because of badly installed insulation.
In this case, a laudable and well-meaning scheme to make homes more energy efficient in one of the poorest parts of Wales has had the opposite effect, with profound physical and mental health consequences.
Many residents we spoke with say they’ve developed breathing problems, including Julie Goodridge who was diagnosed with chronic obstructive pulmonary disease (COPD), while others have suffered terribly through stress and anxiety. Some victims have spent more than £20,000 or their own money trying to fix the problem.
The real scandal here though is the way victims have been ignored for a decade. The lack of urgency shown by Bridgend council to repair these ruined homes caused by its own bungled scheme has driven residents to despair.
Last month the Welsh government announced it was to provide £2.65 million of funding over three years to repair the homes “to ensure we make a positive and lasting difference”.
Bridgend council will contribute more than £800,000 but has announced no start date yet for the work - a spokesperson said it would take at least a year to complete.
Meanwhile, residents are preparing for another freezing winter in damp, mouldy and unsafe conditions.
Want a quick and expert briefing on the biggest news stories? Listen to our latest podcasts to find out What You Need To Know