That depends where you are. Here in Australia the default is single glazed windows, and double glazed is hideously expensive, especially to retrofit.

Sounds you're somewhere with some actual building standards though.

Also in australia, the BCC/NCA is an absolute joke compared to basically every other industrialized country. There’s a reason for the annual “Austrlian houses dont meet WHO minimum standards” articles.

As an example single pane windows havent been effective or widely used since the 70-80s in north america and europe. And both places energy standards effectively preclude them since 2000ish. Or insulation in australia is effectively absent in pre 2000s, and maybe R-4ish on a new build now. Conversely NA was R-4 in the 70-80s and it would be about R-6 (or more) these days.

Our residential solar and heat pump uptake is great. But for building standards and quality were a joke.