The numbers
The test was carried out on 11 August 2026. Because Pulse measures at 4 Pascals rather than 50, the report gives two figures. The measured result at 4 Pa was 0.60 m3/h.m2, which extrapolates to 3.26 m3/h.m2 at 50 Pa. The RdSAP default assumption, used when no test is done, is 15 m3/h.m2.
Air permeability is conventionally quoted at 50 Pa, so 3.26 is the figure that goes into the assessment. Elmhurst describes a result around 3 to 4 as very good. Against a default assumption of 15, that is a substantial correction, and it was there all along, just never measured.
The result
The reassessment came back at a C with a score of 72. That is comfortably over the line, not scraping it.
The modelled carbon emissions on the new certificate are 2.7 tonnes a year, against 4.2 tonnes on the old one. Some of that gap is the change in methodology between the two assessments, which were six years apart and use different fuel emission factors, so it is not a like-for-like comparison. But the direction and the rating uplift are real.
What makes the result more striking is that the current methodology scores some features less generously than the old one did. The property reached a C anyway, because the two things we changed, the loft and the airtightness, more than made up the difference.
Why the timing matters more than the score
The new certificate was lodged on 19 August 2026 and runs to 18 August 2036.
Under the confirmed Minimum Energy Efficiency Standard, privately rented homes in England and Wales must reach EPC C by 1 October 2030, with a cost cap of 10,000 pounds per property before an exemption can be registered. The requirement applies to all tenancies from the same date.
The detail most landlords have missed is this. A certificate at C or above, lodged under the current metrics before 1 October 2029, counts as compliant until it expires. This one was lodged in August 2026, so the property is compliant through to 2036 without being reassessed under the reformed EPC that is coming. Getting an accurate certificate now is worth more than getting one later.
What this actually shows
The lesson here is not that an air test is magic. It is that accurate data and a couple of well chosen improvements beat guesswork.
The old certificate was holding the property down in two ways. It assumed the worst on airtightness, because the building had never been tested, and the loft was genuinely under-insulated. Fixing the real weakness in the loft, and measuring the real airtightness instead of assuming 15, was enough to move a high D into a solid C.
For a property that is already close, that combination is often far cheaper than the heat pump or the external wall insulation people assume they need.
What it means for landlords
If you have a rental sitting on a high D, it is worth finding out two things before you spend on anything big. What is your loft actually doing, and has the airtightness ever been measured or just assumed? Very often that is where the cheap points are hiding.
We check the certificate first, tell you which measures will genuinely move your rating, and only take on the work where it stacks up. On the air test itself, our terms are simple. EPC C or no fee, subject to our published terms.
Check what your rating is really worth
Thermova helps landlords across England and Wales reach EPC C the accurate way, with measured data and targeted improvements rather than guesswork and overspend. Send us your D-rated addresses and we will tell you, free, where the cheap points are hiding.
Book a free check: https://thermova.uk/epc-compliance/
Why Your EPC Score May Be Wrong, for how assumed values pull a rating down: /blog/epc-assumed-values-air-tightness-testing/ How Much Does It Cost to Get an EPC From D to C, for every route compared: /blog/epc-d-to-c-cost-comparison-uk/ Pulse Air Tightness Testing Explained, for how the test itself works: /blog/pulse-air-tightness-testing-explained/
The Home Energy Model, for what happens to EPCs after the reform: /blog/home-energy-model-2027-epc-changes/
All figures are taken from the property's Energy Performance Certificates on the public register and from the Pulse air permeability test report dated 12 August 2026. The D rating was lodged on 13 November 2020 (certificate 9190-2553-6090-2100-2121) and the C rating on 19 August 2026 (certificate 0300-2729-5680-2496-2581). The improvement reflects a loft insulation upgrade from 100 mm to 300 mm and a measured air permeability test of 0.60 m3/h.m2 at 4 Pa, extrapolated to 3.26 m3/h.m2 at 50 Pa, replacing the RdSAP default assumption of 15, reassessed under RdSAP 10. Carbon figures are modelled outputs from two different assessment methodologies six years apart and are not a like-for-like comparison. Yearly energy costs are not compared here because the two certificates were produced under very different energy prices. Published with the landlord's permission.