Doors and Windows - Double Glazing Retrofit

I have cedar timber framed windows in our house. Considering double glazing for insulation by rebating one side of the window frame and inserting another pane of glass. My question is how to control moisture between the two panes.
I have heard of using dessicant. I only know it as the packet of little balls you get in packaging. Has anyone some ideas?

Double glazing is not something you should attempt to build yourself since you will probably not be successful if you try. A similar question and replies can be found here (http://forum.doityourself.com/showthread.php?t=327432).

It might be possible to have insulating glass units (IGU's) custom made for your windows and retrofit them, but making the IGU's yourself is out of the question.

2 single panes of glass could be combined (not as a sealed IGU, however) provided there is ample air space between the panes and ample breather tubes around the perimeter so that moisture does not build up between panes. Andersen used this method for a period of time without problems, provided the breather tubes remained clear. Pella still uses this method on sashes that come equipped with an interior storm panel.

As usual, I'm in 100% agreement with XSleeper.

Trying to build your own double pane windows, and then having them NOT for up -- chances are that's just not going to happen -- will prove to be a waste of time and material.

(IF you were successful in building them and they didn't fog up, that would be an indication that they really aren't any more energy efficient than a leaky single pane!)

Talk to the folks at a local glass shop. They MAY be able to get IG units that could be installed into your existing frames, but don't count on it.

The tried and true way is to replace or retrofit your windows.

Thanks for the quick replies.

Could you explain the idea of "single panes of glass could be combined (not as a sealed IGU, however) provided there is ample air space between the panes and ample breather tubes around the perimeter so that moisture does not build up between panes. Andersen used this method for a period of time without problems, provided the breather tubes remained clear. Pella still uses this method on sashes that come equipped with an interior storm panel.

May be what I am already thinking about but had not thought of the breather tubes method to control moisture.
Lockwood16

Some Andersen wood sashes used to have two single panes of glass that were separated by an inch or so. In the space between the glass, 3/16" holes were drilled every 12" or so to allow fresh air into and out of the space between the glass. As mentioned, this is certainly not as energy efficient as an IGU, but it would be an improvement over single pane glass.

Pella still features some sashes with a similar setup, but they have a hinged storm panel on the interior, and the breather tubes (3/8 x 1/4" square plastic tubes with a bug screen) are on the 4 corners of the sash.

Why not just buy new Insulated Glass units, depending on the size they usually are not all that pricey. I'm sure there is a glass shop near you, they usually have someone that could measure for a small charge. As for the dessicant, I believe it is used in the spacer channel of Insulated Glass Units as a moisture absorber, but is really only meant for any moisture that may be in the unit at time of production. The seal keeps moisture out, but when that seal goes, it is only a matter of time before the dessicant absorbs all the moisture it can hold, and your glass is foggy. Economically I think you might be making a mistake by making your own Double Pane window, but if it's for bragging rights, I say go for it. I doubt you could get a professional to do this "upgrade" and warranty it.