In case you don’t want thick double glazing, slim double glazing has width of only all around 14mm (although some are as slim as 10mm) and is much more successful. The U-Worth (the measurement that implies the window’s thermal efficiency) is healthier and slim glazing is much more aesthetically satisfying. https://brooksmfyph.blog4youth.com/36470105/how-much-you-need-to-expect-you-ll-pay-for-a-good-sash-windows