Closing window cavity

[Lu_Na]

Hello everyone, I was hoping to get some advice on how to proceed with finishing off our windows.
We had windows changed and moved forward so they sit flush with the outside wall. We’re left with cavity on the inside, which mostly have battens in the cavity gap (left, right and top side).
Decorators used additional battens where needed as openings were asymmetrical and fixed plasterboard to create reveals. I’m worried though that not using insulation (kingspan or plasterboard with insulation) to prevent reveal getting cold and creating condensation will cause us issue. What would be the right thing to do? Reveals aren’t plastered yet, so if I need to take the plasterboard down now is the good time.

In case above is ok and insulation is not needed, should we use something to close cavity before sill is fitted (definitely a gap there as per picture)?
Pictures before and after reveals we’re fitted. Thank you!

 

[Swwils]

Why have you had the windows put flush on the outer wall???

You will now need fully insulated reveals.

 

[Lu_Na]

Hi @Swwils Because it looks better! Our old windows weren’t fitted properly anyway, were really cold and we had issues with mould. The reveals were just covered with pvc. I’m keen to do it properly but unfortunately haven’t realised on time we need to close the gaps properly. Would kingspan be a way to go?

 

[Swwils]

Can treat it like installing internal wall insulation to a retained window, try your best to seal from air now that you have access too, top up the cavity insulation.

If you have a metal lintel above take particular care there as that is now a metal thing that's outside being brought into direct contact with your final plasterboard in the warm room unless you insulate it.

In newer details the windows are usually set at least 30mm over a cavity closer, so your internal finishes don't touch outside surfaces.

 

[Lu_Na]

@Swwils I’ve read about 30mm rule earlier today, no idea why window installers and their surveyor didn’t mention this to us.
We don’t have metal lintels, just concrete ones.

Thank you for all the info!