Window insulation

[KarlisR]

I am intending to insulate my windows for many reasons, one is obviously an excessive heat loss especially during cold times. All my windows are double (as you can see in the picture) - pulley type & single glazed windows. The frames in between appear to afford to squeeze in some extra insulation. Does anyone has come across a similar setup and could advise about the best technique and materials (pref. cost-effective) to go about this sort of job?    

[Roundtuit]

What you have there are double-hung sliding box sash windows, with secondary glazing fitted internally.  I can't see much merit in trying to insulate the reveal between the glazing systems if that's what you're suggesting; perhaps better ensure that your sliding sashes are fitting properly and fit draught seals. It's possible to replace the parting bead with a flexible seal, and rebate a weather strip into the outside of the top rail on the bottom sash to help keep draughts out, and then make sure the secondary glazing is sealed properly. And fit thick curtains.

[Gone West]

We had secondary glazing on some of the windows in our old bungalow. We found it to be very effective once all the the draughts had been eliminated. So as has already been said, draught proofing the original sashes, and secondary glazing system if necessary, should improve things greatly.

[KarlisR]

Thank you very much for advice. It is very helpful to know! 

[Simplysimon]

secondary glazing doesn't really help much with insulation as the air space is big enough to convect heat. it is usually there to help sound insulation though if well fitted it will stop draughts as previously mentioned. best option would be new windows with dg units and draught strip. next best option would be a clear film applied over the sash to minimize the thickness of the air gap similar to https://www.ebay.co.uk/itm/DOUBLE-GLAZING-FILM-DRAUGHT-INSULATION-KIT-WINDOWS-6sqm/283447135980?epid=2301108758&hash=item41fec40eec:g:2dMAAOSw5lpcrfhB&frcectupt=true we put this in our first flat many years ago. would still require draught strips on sashes.