Secondary double glazing East London

Secondary double glazing with a 100 mm gap will work well. Curtains will do nothing.

He'll also need to block off the air bricks, or they'll sound like small speakers with a feed from the street.

I suspect that the sound will be going the other way!

They also use thicker glass. (More resistant to sound transmision as it is more rigid.) Sometimes they use triple glazing in standard uPVC window frames..

Remember a lot of sound comes in through the roof structure.

Thanks to all for the comments. No airbricks in the room but it is top floor so will be looking at soffit vents and ceiling insulation next time I am there.

My experience with double lined velvet curtains over Critall windows (blasted Grade 2 listing!) has been quite good, for noise as well as cold air.

They'll stop people on double decker buses looking in and seeing the source of the 'noise' :)

I don't know if they do secondary DG but the below have been around for donkey's years, and did a good job on a house near me c.15 years ago. (I've only used to supply bits of glass and mirror and a small sealed unit but IIRC same blokes over the years, and same name, so not in the habit of doing a phoenix.)

In article , newshound writes

Your experience matches mine but closing the curtains in daytime seems a bit extreme :-).

I wonder, has your son followed the draught exclusion plan on the existing windows yet? I did this on my (huge) sash window set and the noise reduction was impressive. These were multiple traditional sliding sash units of approx 1m width and 2.2m height glazed in 1/4" glass.

You can get an approximation to what you might gain sound wise by sealing the gaps with PVC tape and unless your paintwork is seriously far gone then it should peel off without damage.

The original work I did here with plastic sliding V-seals has broken down through age and I used the PVC tape trick to limit draughts and noise over the last winter. Frames are white painted here and white 20mm PVC tape was a good match, 50mm over the bit where the sashes join (what's the name again?).

I do realise that that this tangent is more work than having a man in and not what you asked for but thought I would mention it nonetheless, in case it helps.