Take note: These values are for the middle of glass only. They should only be employed to match the impact of different glazing varieties, not to compare overall window items. Frame choice can considerably have an affect on functionality. These values characterize double glazing that has a one/2″ air gap. https://fire-rated-secondary-glaz40505.blogdosaga.com/36669203/little-known-facts-about-secondary-glazing-london