Window Regs

josip

5 years ago we got our aluminium apartment windows replaced with PVC.
One of the windows extended out from the wall and had small side glass panes.
It was a struggle at the time to meet the regs (by way of thicker frames) and fit the window in the existing 210mm space. In the end it overhung by 20mm.

Roll on 5 years and a neighbour's apartment is also getting their windows replaced. Their builder is telling them that the regs have changed since ours were done and to meet the new regs, the frames have to be 79mm and it's not possible/pointless to get a pane of glass 50mm wide.

I've no idea what the regs say, but have there been new regs governing window U values in the last 5 years?
Does 79mm frame thickness sound reasonable to those in the know?

Gumbo

Part L (conservation of fuel and energy) of the building regulations has changed, quite dramatically too.
If replacing like for like, all you have to do is at least match the current windows spec iirc.
Once the window is. It a means of escape window I wpuldnt see a problem with replacing with a window that doesn't fully meet today's standards aslong as it doesn't make the situation worse than what's there at present.

Drift

Is it possible that the builder just doesn't want to go to the effort of getting the smaller frames?

It is not difficult for window manufacturers provided they can source the narrower frame - which afaik is still possible.