12/18/2024
Did you know that exterior secondary windows can extend the lifespan of insulating glass units (IGUs) by up to 3x?
At INOVUES, we assess each building before recommending one of our interior or exterior retrofit systems as a non-invasive facade/window upgrade solution. In some cases, adding an exterior secondary glazing could be better or more appropriate than an interior window insert, and vice versa.
For example, one of the benefits of using our insulating glass retrofit (IGR) system as an exterior attachment over double-pane windows is improving their internal condensation/fogging resistance by up to 280%. Here's how:
By turning double-pane IGUs into triple-pane glazing and creating a new insulating weather barrier in front of the existing windows, our IGRs increase the IGUs' Condensation Index (CI) from 30 to 84 (per NFRC on a scale from 0 to 100 -- see the attached diagram).
We validated this at one of our projects last winter, where ~20% of the non-retrofitted IGUs fogged and needed to be replaced, while none of the retrofitted IGUs did.
Interestingly, if the same IGR system were used as an interior secondary window, the CI would not improve. In fact, it would decrease slightly, from 30 to 28, as shown in the diagram.
This is especially important for buildings that have double-pane windows that are near the end of their 20-30-year lifespan (about 30% of all buildings). An exterior IGR retrofit can extend their lifespan potentially by up to 60 years, avoiding costly replacements.
If you'd like to learn more, we’ve covered this topic in detail in our latest white paper. Reach out to us if you’d like to get a copy!