Section of missing PIR in wall now needs EPS retrofit?

[ruggers]

EPS bead info. required.

 

Im building a house which has a ground floor integral garage to house cavity divide wall. The full 6m length of the 2475mm high wall was supposed to have 100mm PIR insulation in a 110mm gap, but the builder decided that the end 1.35m section which is out of the garage and only separates the hallway to utility didn't require insulating because they are internal rooms. 

 

He's clueless to heat loss and this section is still part of the same cavity wall linked to the rest of the house cavity. theres the 10mm air gap, plus the 225 between the underside of the PIR installed and the bottom of the cavity.

 

Because I'm still able to look down this cavity from the top because the first floor hasn't yet been installed, I'm thinking my best option would be to add some EPS from the top and pack it down. I luckily have a lintel section at the bottom of this void for UFH pipes, which means I have top & bottom access and could use expanding foam to squirt in between the bottom of the PIR & the cavity base to seal off the air & stop any EPS being lost.

 

I'll require 0.4m3 or 14 cu feet. Where could I buy this or any other advice would be appreciated?

Edited July 28 by ruggers

[Nick Laslett]

@ruggers, I used Thermofloc, for a similar problem. 
 

https://www.ecomerchant.co.uk/thermofloc-loose-fill-cellulose-insulation-12kg.html?srsltid=AfmBOoqo9DLSk6Bu1OfNCWrbfDJHnqhT4aZgcLG_cKt7wAmK0fomDcFT

 

[ruggers]

Thanks Nick.

 

I brought it up today and they actually took one side of the wall down and installed the missing PIR after their outburst. A decent outcome i never expected.

[Mr Punter]

A good result.  Did your builder use insulated cavity closers on the sides of openings for doors and windows, or close them with blockwork as per the drawings?

[ruggers]

On 28/07/2025 at 19:03, Mr Punter said:

A good result.  Did your builder use insulated cavity closers on the sides of openings for doors and windows, or close them with blockwork as per the drawings?

I'm using the cavity closers and also adding a little onto them so I have 100 continuity all round and no block returns at reveals.

I'm using T&G PIR and doing it all myself to ensure it's fitted correctly and all mortar is removed.