This article accompanies a podcast we did with Rob Divelbess, owner and principal at Olympic Glass on Bainbridge Island.

In this podcast we discussed

  1. Failed seals or “blown IGU’s”
  2. Melted vinyl window frames
  3. The myth of windows and energy efficiency
  4. Window coatings

1. Failed Seals

  • Lost seals are a common finding on a home inspection. Here are a few things we learned from Rob.
  • The folks in the window industry would call a lost seal a blown IGU or Blown Insulated Glass Unit. A lost seal, however, is a fine terminology.
  • The term desiccant strip is no longer really correct. However, the use of desiccant below a metal strip is still the basic technology that prevents condensation inside an insulated glass unit.
  • Newer windows are less prone to condensation than the older ones because they put more desiccant between the panes of glass – thus thicker glass units.
  • The window fails when the desiccant becomes saturated and can no longer wick condensation.
  • When extensively failed, meaning the metal channels are rusting, you could make the case that repair is urgent and somewhat a structural concern.
  • Mildly failed seals are cosmetic.
  • When you think your window is leaking, be sure you check the weep holes. Obstructed weep holes will cause water problems with your windows.

2. Melted Vinyl Windows

This is something I see occasionally on houses with a lot of solar exposure – think south and west facing with big views and often on the water. I have seen this a number of times over the years, especially in 1990’s era houses on the water. Because of this, I have been wary of vinyl windows on exposed houses. Rob straightened be out here.

According to Rob, newer vinyl windows contain titanium dioxide in the frames. This is almost like a sunscreen that helps reflect punishing UV rays and helps prevent UV damage to vinyl frames. According to Rob, this melting of vinyl frames should not be an issue with modern frames. though it is something you should watch for on exposed houses from the 1990s.

3. The Myth of Windows and Energy Efficiency

If you are hoping to pay for your new windows with all of the money you will save on your energy bills, don’t hold your breath. You are not likely to be alive by the time that happens. Rob and I discuss that there are many reasons to update your windows: improved comfort, better looks, reduced risks of condensation and more durability. One important consideration is to try and roll window updating into siding updating. Installing new windows can be traumatic for the siding system and ideally, the two systems are replaced together, providing an installer to properly address flashings, weather barriers, and critical transitions.

4. Window Coatings

Window energy coatings are designed to help manage solar gain and radiation in a house. Choosing the right energy coatings for your house is complex because if you block too much UV, you can create a dark house; more is not necessarily better. The best advice if you are purchasing new windows is to consult with a local professional about the window coatings most commonly used in your region. Also note that some of the time you think you are looking at a lost seal, you are probably looking at a failed window coating.

This photo shows an example of the different window coatings