DG fitted directly into existing SG windows

[heatherstev]

Existing windows have very good heavy wood frames which I am reluctant to replace. One possible solution is to fix new DG units into the insides of existing frames, with very thin spacing bead between them and existing panes. One problem would be condesation between two but with small volume of air and limited circulation this may be minimal, especially if drainage is allowed for.
Thoughts please. Also anybody see any additional problems?

[acsimpson]

Are you talking about using double glazed units which would be supplied as a unit or glazing them with 2 sheets of glass and a wooden bead between them.

If it's the first the the units would be presealed and condensations shouldn't be a problem, but if your frames are off square then you may have difficulty measuring, ordering and fitting the units. The units would need to be measured and manufactured very precisely to fit the existing frames.

If you're thinking of the latter then codensation might be a problem depending on local conditions. I'm afraid I can't advise how much of a problem though. Are you aware of a product which can be stuck to the frame and shrinks when heating which can give most of the benefits of a second glazing with minimal cost.

Finally have you fitted draught excluders? They are normally the biggest single improvement single glazing can get.