Ortogonal to the discussion, but I think in an odd way, Australia is one of the most similar countries to Spain in this aspect. Very limited to no natural gas proliferation, electric heating, if any, but houses made rather cheaply but somehow still ending very expensive. I've seen houses near Melbourne resembling a tin hut costing AU1.5M. According to weatherspark, some Spanish locations have their climate counterparts in Australia, e.g. Perth is most similar to Malaga.
True true. The old housing stock is poorly insulated. I mean: not at all insulated, and retro fitting insulation is painfully expensive.
Sure, insulation in ceilings is relatively easy to do, but swapping windows out for double glazed windows with solar thermal reflective film, very expensive.
New homes are much better designed, requiring wall and ceiling insulation and double glazed windows or better.
And yeah, the state of Victoria is still prompting banning new homes even connect to gas. Seems strange when we export around the same volume of LNG as Qatar.