Replacement Window Building Regs - am I being lied to

[lauraknightc]

We’ve had new windows installed by a Certass registered company, the windows are installed in the cavity. We are having some issues related to mismeasurement however upon further inspection there has been nothing added to the cavity.

we have asked questions to be clarified around whether it meets building regs but are being told that expanding foam in the cavity is suitable and they couldn’t use cavity closers because of the install being in the cavity.

not sure what to believe!

For new build they should avoid thermal bridging, aside from that they should not leave it worse than before.
Expanding foam is usual for filling around the packers but in the cavity would be wasteful and would still need a backer of some kind. I guess it's a fix-all kind of thing rather than best practice.
How did they install it in the cavity, it would need to rest on something structural, not just floating, did they bridge the cavity with plates and mount the windows on brackets back to the inner leaf? That is better for thermal performance for sure.
Were there cavity closers before and they have removed them? I think it will probably be certified by them regardless but if you don't think it's right maybe you can escalate to their professional body.

There wasn’t anything in before, it’s been installed to the front of cavity (closer to the outside) they’ve got one screw going into the internal brick and then a block of wood (max 150mm) long somehow put into the cavity for an additional fixing and then screwed wood into the wooden lintel to bridge the gap that was left for under measuring and screwed into that.

The expanding foam is just on the inside and there are gaps between the brick at the front and the window which they will trim and then seal the edge of the trim.

they’ve also said they were short but that it’s not that much so they could install from the exterior.