GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Is is possible to install additional glazing over an existing window?

JBrinkman | Posted in GBA Pro Help on

I live in NW Ontario, Canada fairly cold climate. I have an existing house built in 2009-10. It is built on a sloping lot facing south with a proux front made up of mostly windows. The glazing installed is dual pane with low E and argon, there was a mistake and the wrong glazing was sent. Orginally some of the south facing glass was to be tinted to help reduce glare, however clear glass was sent and due to our remote location and the time involved to get the replacement glazing the windows were installed as is. The replacement tinted glazing is here, it will be switched with the existing glazing, my questions are:

1. Can the removed clear glazing now be installed either on the exterior or the interior of the replaced glass?
2. Will the installation need to be completely sealed or should it be vented?
3. Is there a recommended spatial separation between the glazing units?
4. Finally, is it worth while to even attempt this?

Jody Brinkman,
Sioux Lookout, ON

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Dovetail7442 | | #1

    Jody, I'd be reluctant to try using the replacement glass to augment performance of the new glass. In my experience it's very difficult to keep condensation from occurring in the panes facing each other.

    That said, Pella offers a "double glazing panel" that essentially does what you suggest. It's a removable inside storm window, that's gasketed and vented to the outside. DGP's pre-date insulating glass and these days most folks who want high performance windows make use of triple glazing: sealed insulated units.
    Perhaps you can re-use the replaced units as a greenhouse.

  2. JBrinkman | | #2

    Chris, thanks for the response. Condenstion has been my concern as well, would installing the replaced glazing about 1/2" from the installed glazing on the interior allow for enough room heat to help keep both units warm enough to prevent condensation?

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |