Landlords told to prepare early for EPC C 2030 upgrades
2 weeks ago | 15 comments
Double glazing issue under the latest RdSAP10 EPC standards?
8:07 AM, 4th June 2026, 2 hours ago
3
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Hello, I’ve just been just been shafted as I’ve had a couple of new EPCs done to ground floor flats, both fully D/G windows throughout.
Got a worse rating within the EPC for the window rating than the previous even though they are exactly the same windows!
Now rates the windows as ‘poor’.
Windows are fully functional and no issues, not blown or anything, all uPVC in place no deterioration etc. It all boils down to the fact that I cannot confirm the date when they were originally fitted. This is getting to be a joke now.
RdSAP 10 window categories explained (current rules):
Under RdSAP 10, double-glazed windows are recorded using specific evidence-based categories.
These are the options assessors must use:
Double glazing – unknown install date
Used when the property has double glazing but no proof of age or specification is available.
Default conservative assumptions apply, often resulting in a “poor” rating.
Double glazing installed before 2002
Reflects pre-Building Regulations standards.
Assumed higher heat loss and higher U-values.
Frequently rated “poor”.
Double glazing installed between 2002 and 2022
Improved regulatory standards and better assumed performance.
Requires evidence to be recorded.
Often rated “average” or “good”.
Double glazing installed during or after 2022
Modern glazing standards and lowest assumed U-values.
Typically rated “good”.
Double glazing – known data
Used when installation date and specification can be proven with documentation.
Allows more accurate EPC inputs and usually improves the window rating.
If no evidence is provided, the assessor must default to the least efficient reasonable category.
3. No supporting evidence was available
Without evidence, assessors cannot guess.
Acceptable evidence includes:
FENSA certificate
Building Control sign-off
Installer invoice
Manufacturer specification
Documentation showing installation year
No paperwork = default values.
Thank you,
Reluctant Landlord
Tags:
double glazing, energy efficiency rules, EPC ratings, FENSA certificates, landlord compliance, RdSAP 10, rented house epc
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Member Since May 2024 - Comments: 76
9:57 AM, 4th June 2026, About 6 minutes ago
We live in a clown country. I am beginning to hate this business.
Member Since January 2022 - Comments: 10
10:01 AM, 4th June 2026, About 1 minute ago
The gap between the double glazing panes, coatings used, and the material used for the spacers around the perimeter (they hold the two panes a consistent distance apart) all make a big difference to the performance of a window. Older D/G units may be in good condition, but an 18mm D/G unit with an aluminium spacer is far less thermally efficient that a 22mm D/G with a plastic spacer, and much less than a triple-glazed unit.
I would argue that most EPC surveyors should be able to tell the difference and use a generic figure, BUT the new versions of SAP use far more data to give a more accurate (but still a lot of assumptions) picture of the building performance. It’s not PHPP levels of accurate energy assessment, but much better than the old RdSAP. As a Passive hOuse Consultant, I’m seeing more and more Landlords looking for accurate energy modelling, so they can see where their money is best spent, rather than just hoping for the best when the EPC needs renewing.
Take it as a warning for all landlords; keep quotes, specifications, etc for everything. Save pictures (or better still the original) energy labels, and hand a copy to the assessor to get the most accurate rating.
Member Since October 2024 - Comments: 12
10:02 AM, 4th June 2026, About 10 seconds ago
The descriptive rating of poor does not impact upon the EPC rating itself, as it is merely a separate calculation outside of the EPC rating methodology. What the descriptive column of poor is now “comparing” itself with is what is now considered the best generally available glazing i.e. Triple Glazing, in other words this is now considered to be the “norm” going forward.
If you can provide the full address I will see if I can locate evidence of a Fensa certificate as these are publicly available, albeit if you want a copy of the actual certificate you would have to pay. The record that there is a Fensa Certificate however is free to see.
Depending on locality of building I may be able to find a Building Control record for you, but this is sometimes less publically available as each authority has its own accessibility rules.
I would suggest your rating has not got worse due to the glazing, but to other additional inputs that now have to be put into the EPC software including, but not limited to, ventilation systems such as extract fans.