What type of glazing putty to use with an IGU?

fromhollywoodDecember 13, 2009

I am making some insulated glass storm windows. I'm ready to insert the IGU into the wood frame but not sure the best way to do this. I've read you don't use the white putty- like glazing compound as you would on a single piece of glass in a wood frame.

I'm first going to put some thin, flat glazing tape which will sit between the glass and the wood frame. The tape I'm using is 1/8" thick and 3/8" wide.

After I put the insulated glass against this tape, how do I hold the glass unit in place? What I'd do with a single piece of glass is to use the push points and then apply a layer of glazing putty such as Dap 33.

I assume its ok to use the metal push points with an IGU but the bigger question is what type of glazing compound do I use to finish it off and hold the glass in place?

Here is a photo of the IGU sitting in the wood sash (but nothing yet holding it in place):


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Most all insulated sash and units that i have scene are held on place with silicone caulk of a high quality

    Bookmark   December 14, 2009 at 11:21AM
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Hiya Hollywood, welcome back!

From the picture looks like nice work on the storm window, although how tight is the IG in the sash? You want to leave a little bit of "wiggle room" in there because both the glass and the wood is going to expand and contract depending on weather conditions. If you are in SoCal, then it won't be as drastic as some areas, but there will still be some movement.

Also, I would suggest using glazing blocks or small spacers between the glass and the wood as well to keep the edge of the glass from touching the wood. If the glass and wood do touch, it might not be a problem, but it could be since wood will carry moisture and that moisture could transfer to the IG unit via a bit of capillary action and it is possible that the moisture could affect the IG long term.

And I am very curious how you ended up building the IGU.

Typically, IG's are held in place using wood stops on both sides of the glass - one fixed and one removeable.

The manufacturer may use glazing tape, glazing putty, silicone, or whatever between the stop and the glass to seal the glass to the wood. Glazing tape is very common on the fixed side and silicone or putty is more common on the removable side.

I am assuming that the glazing tape that you used is two sided? It sticks to the glass and the fixed stop? If so, then the IGU will be held securely in the frame no matter how you do the other side. If it is one side sticky and the sid touching the glass isn't the sticky side, then you would have to make sure that the removeable side is secure of course.

If there is room, I would use a wood stop and silicone. If there isn't room for a wood stop then I wouldn't have an issue with using glazing points and window putty like you would use in a single pane - again keeping in mind that you want to keep the edge of the glass (IGU) off of the wood.

Really interesting project.

    Bookmark   December 16, 2009 at 7:00AM
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