Most improved, twice? What really happened in TS1

The claim: top of the table, two years running

We rank postcode districts by how far their share of homes below C fell between editions, counting the 26 districts with at least 2,000 homes on the register. TS1 came first in both years. In the year to July 2025 it fell five points, from 63.4% to 58.4%, well clear of Eaglescliffe in second. In the year to July 2026 it fell another three, to 55.4%, ahead of Redcar & Marske and three Hartlepool districts.

It didn't come from nowhere. In the year before that, TS1 ranked tenth. So "twice in a row" is exactly right, and "three times" would not be.

The catch: half of the first fall wasn't upgrades

A district's share below C can fall for two reasons. Homes already on the register get re-assessed at a better rating, or homes appear on the register for the first time, already at C or better, and dilute the total. Only the first is improvement.

In the year to July 2025, 517 TS1 homes joined the register, and 82% of them were already at C or above. Some were new builds (111); most had simply never had a certificate before. Together they account for more than half of that year's five-point fall. Re-assessed homes account for 2.2 points. That was still the most of any district, so TS1 earned the first title on upgrades too, but by a smaller margin than the headline suggests.

In the year to July 2026 the picture flips. Re-assessed homes account for 2.3 of TS1's 3.0 points. But on upgrades alone, three Hartlepool districts did slightly more, and TS1 comes fourth. The difference between first and fourth is under half a point, but it's real, and the second "most improved" owes something to the 115 new homes built in TS1 that year.

What does stand up: TS1's homes really are improving fastest

Strip out the newcomers and take the long view, and TS1 is still out in front. Across every home in the Tees Valley with more than one certificate, the average gain from first certificate to latest is 4.9 points. In TS1 it's 8.3 points across 4,299 homes, the highest of any district with at least 1,000 re-assessed homes. Darlington's DL3 is next, at 6.9.

Over the last two years, four in five re-assessed TS1 homes came back with a better score, and across all of them the average change was close to nine points. Not every one improved: 180 scored lower. Ratings can fall when an assessor records something an earlier certificate assumed, and the assessment method itself was overhauled in June 2025.

Who did the work: private landlords, re-letting

Over half of the TS1 homes that crossed into C were privately rented: 218 of 391. More than two in three re-assessments were triggered by a new letting, which is the 2030 rental standard doing what it was designed to do. Landlords are upgrading between tenancies and getting a new certificate to prove it. In the year to July 2026, privately rented homes that were re-assessed gained 10.6 points on average, against 7.4 for social housing and 6.6 for owner-occupiers.

Grants played a small but growing part: 39 re-assessments in the latest year were lodged for a grant scheme, up from three the year before.

What got done: four-figure jobs, mostly

When a home is re-assessed we compare its new certificate's recommendations with its old one. A measure that was recommended before and has gone now was, in most cases, done. In TS1 the list is led by the cheap and quick: lighting, heating controls and boilers, all jobs a landlord can fit between tenants.

Solar PV is the one to watch. It only cleared on 72 homes, but 57 of them crossed into C, the highest hit rate of any measure. Where a roof suits them, panels are often the single biggest jump on a certificate's list.

Disappearance usually means installed, not always. We leave out solar water heating and wind turbines, which dropped off certificates because of the June 2025 method change, not because anyone fitted them.

Street by street

Ayresome Street did more than anywhere else in TS1: 41 homes re-assessed, 24 of them crossing into C. The pattern repeats along the Victorian and Edwardian terraces behind it (Longford, Harford, Meath and Portman Streets), where re-assessed homes gained between six and ten points on average.

Linthorpe Road shows how messy real data is. Eighteen homes crossed into C and only one fell below it, yet more of its re-assessed homes lost points than gained them, and the average change was slightly negative. Nearly all of them are flats on the town's main shopping street, many sitting just either side of the line, where a few points in either direction decide the band.

And the work is far from done. On most of these terraces, seven or eight in ten homes are still below C.

What's left: the cheap points are going, the walls remain

4,649 TS1 homes are still below C, which is 55.4% of the district. The good news is that 1,263 of them are within five points of the line, a gap that lighting, controls or loft insulation can often close. Low-energy lighting is still on the recommendation list for 1,819 of them.

The harder truth is the housing itself. Two-thirds of TS1 homes are solid-brick, and more than half were built between 1900 and 1929. For 1,831 of the homes below C, the first thing the assessor recommends is internal or external wall insulation, the most expensive job on the list. The next two years in TS1 will be decided by how many of those homes find a cheaper route to C first, and by honest re-assessment after every phase of work.

That's the gap our Retrofit Roadmap is built for: it puts the recommendations in order, prices them, and shows which ones actually get a home to C.