Use anonymised Energy Performance Certificate survey data to offer insulation upgrades

If you would tell insulation companies which postcodes contained homes without cavity wall insulation, they could target their sales people there, as homes in one postcode are usually the same age and construction. Or you might allow people to opt in to an annual direct mailing that sent people offers relevant to them having, say, an oid boiler that should be replaced. This could be set up so that reputable companies did not get the address information themselves. If insulation or heating installation companies can get more customers in one place they can afford to reduce their prices.