The excellent news is that secondary glazing when placed in close proximity to the main window can offer excellent thermal enhancements. As far as toughened glass, The essential solution is often 4mm toughened glass. From there, you could update to 6mm toughened glass for improved thermal insulation and audio reduction. https://window-refurbishment77653.blogolize.com/how-much-you-need-to-expect-you-ll-pay-for-a-good-noise-reduction-secondary-glazing-66249433