The problem
From 1 October 2030, privately rented homes in England must hold an EPC rating of C or better. Around 1.4 million London homes sit below that line. Landlords don't know which of their properties are exposed, installers don't know who to call, and the data to answer both questions is public but scattered across three datasets nobody had joined.
What we built
A pipeline that ingests every EPC certificate in London, de-duplicates to unique properties, flags private-rental signals, and matches corporate owners through Land Registry's commercial ownership data. On top of it: a public postcode lookup, a report request flow, and a back office that ranks owners by exposure and tells them which property to start with and which qualifies for exemption.
What the data said
Only about six per cent of sub-C rental homes have a traceable corporate owner; the rest belong to individuals the data deliberately hides. That one number changed the business: the product sells to the ~1,400 mid-sized portfolio companies through outbound, and reaches individual landlords through letting agents and accountants instead of a name list.
What I'd tell another founder
Sell the ranking, not the report. Everyone can produce a PDF; the value is telling a portfolio owner which door to knock on first. And when the data says your obvious channel is closed, believe it the first time.