Worth converting to double glazing?

[Graemevw]

Our house has single glazed upvc windows. Its ex council.
They have a wedge profile outside and on the inside there is a 12mm or so spacer between the frame and the seal.

Windows are all in good condition but i assume there pretty old.

I cant afford to fit all new windows so wondered if its worth getting slim DG units made and fitting them myself.
Other houses in the street have the same windows, but double glazed so i know its possible, but financialy is it worth it? Will slimmer units be as effective?

So i can get an idea of price, is there a general price structure, for example a price per square foot, for DG units? I know there are many different specs to choose from but have no idea what would be the most cost effective option.

The house is already fully insulated.

A seperate issue that is in the back of my mind is there are no vents in any of the windows. Should there be? If so, can they be retro-fitted?

Thanks.

 

[foxhole]

Slim dg is better than a single pane , cost vary around the country take measurements to a few local glaziers and ask them to quote for the whole house [cheaper than doing a few at a time]. You can retro fit vents but if ex council you probably have room vents? in which case additional are not required.
If neighbours have them ask where they got them and price if they are forthcoming.

 

[Graemevw]

I bricked all the room vents up, hate the things.
I sealed them with tape for a while and there seemed to be no issues so they got filled.

Ill talk to some local companies, see what they say about the units.

What spec units is the best compromise of performance and price?