There are actually very few enforced rules about house listings. The market is pretty unregulated. However that house has an epc of C which would suggest its not insulated beyond maybe roof insulation or else isn't well insulated. To get a B or above you need to have a reasonable amount of insulation that you mostly only see in new build properties.

Glad you asked! For a start, as you say, it's Victorian.

For further confirmation, zoom in on the buildings with exposed red bricks and you'll see they're in a Flemish bond pattern, which only appears on solid walls. It's not new enough to have a fake Flemish bond pattern for decorative purposes.

You can also see at roof level, the party wall extends above the slates. Where it's unpainted, it's visibly two bricks thick.

If you can get into the house, you can usually tell from how thick the walls are. On houses with cavity walls, sometimes you can remove the skirting board going through an external door and look into the cavity.

You can also check externally for weep holes, the telltale signs of cavity insulation having been installed, and whether there's a damp proof course.

If you have friends in the area, they'll probably be able to tell you. If you get a survey done (which might be reasonable on a house of this age) they'll probably also be able to tell you. Often the homeowner will know too.

If you get cavity wall insulation installed, they'll drill a hole in the wall to check the cavity with a borescope and take a photo. It's a condition for getting the government grant that they confirm you don't already have cavity wall insulation.

> I think it would help if estate agents were required to list some basic facts about the house — the year it was built, the basic materials for the walls and roof, the type of heating installed.

If you check the 'energy performance certificate' (EPC) it should tell you about the insulation and heating. Of course, the qualifications to do EPCs are minimal so they don't really tell you any more than you can figure out from a house viewing. And estate agents often don't deign to produce the EPC until the house is already sold.

For this house, the EPC is https://find-energy-certificate.service.gov.uk/energy-certif... and states the walls are "Solid brick, as built, no insulation (assumed)"

The land registry's title plan will tell you when it was built for about three quid.

The EPC has the overview I was expecting. I had expected this to be linked from the estate agent's site, and didn't realise there was a place to search for them. (I no longer live in Britain.)