Since quite a few people have been commenting without even googling some data, here we go: https://www.bre.co.uk/filelibrary/pdf/rpts/countryfactfile2007.pdf h

Since quite a few people have been commenting without even googling some data, here we go: https://www.bre.co.uk/filelibrary/pdf/rpts/countryfactfile2007.pdf https://www.bre.co.uk/filelibrary/pdf/rpts/countryfactfile20... Page 3, Summary: Around 83% of homes in each country have some double glazing. Northern Ireland has a higher percentage of homes which are fully double glazed, 62%, compared with 32-44% in the other countries. So, ~60% of the houses are NOT fully double-glazed. In 2007. Srsly. And sure, it's from 2007... but in my expericence, and in talking with a lot of friends, in a main city such as London and in other small cities (e.g. Fareham in the south), the situation is quite similar nowadays...