Tips for DIY secondary glazing please!

[jw52]

I am planning to fix 4mm secondary glass to a fixed 1900s bay window, to reduce heat transmission. The biggest pane is quite large, about 800 by 1100.

There is an existing 45mm deep inner wood frame in good condition, and the external window and putty is sound, so I intend to fix a new 10x15 wood glazing bead inner frame round each existing pane edge, (thus giving me a 15mm gap between the glass panes) using quick grab adhesive, and then to hold the new 4mm glass in place with another 10x15mm glazing bead frame, either held with small screws which I will sink and fill, or more quick grab adhesive.

Is there anything wrong with this plan? Do I need to rest the glass on plastic blocks or bead inside the new frame? Do I need to use silicone sealant too, and if so why?

Your tips are very welcome.

 

[Mw Roofline]

So it will be all fixed in with adhesive? What about access to the bay/ventilation etc?

 

[big-all]

you will not get as good as double glazing
90% off the advantage is from stopping the draughts
if there is little or no draughts then the heat/sound reductions will be minimal if at all noticeable