EPC (energy performance certificate) and defective CWI

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When selling a house, one of the 'services'  estate agents offer is to provide a EPC(Energy performance certificate) for the seller.
If you are selling your house then you must provide a certificate but it's actually quite cheap in the scheme of things (maybe £50-150) and you don't need an estate agent who may add a mark up to it.

The performance is based on algorithm which sums up negative and positive attributes of the house to derive an overall energy rating - it's not based on actual performance.
The Domestic Energy Assessor completing the EPC rating makes assumptions and doesn't check for presence of insulation. They will write things like (flat roof assumed no insulation).

In older houses, retrofit insulation does a lot to push up the rating:



However, what happens when you have damp insulation? Technically It's a negative rating as heating the inside of the house causes large thermal loss via heat transfer through the damp wall into the soggy insulation.
So when we bought our home it's likely that the rating was completely incorrect because it assumes that the CWI is working to specification.

The bizarre thing is, when the CWI is removed, the actual energy performance will be far better in the real world but when it comes time to sell the house the lack of CWI on the check list will result in a new certificate that is markedly worse on paper and this may even affect the sale price.

So really the EPC could be very misleading and by providing an attractive easy to understand summary, it may give potential buyers false reassurance as to the actual performance of a house.
Worse if we issue a new certificate after removing the CWI, the certificate will instruct the buyer that  the best course of action for improving efficiency is to install CWI.

 Update
It was pointed out to me that anyone can become a domestic energy assessor in 5 days by completing this course.
https://www.energy-trust.co.uk/products/domestic-energy-assessor-dea-5-day-course

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