Hollowcore cold air ingress remediation

Yellow_Fern

Hi,

My house has a first floor constructed with 150 mm thick hollowcore concrete slabs. Builders often recommend sealing or 'wrapping' the exposed ends of the hollowcore units at the external cavity wall during construction, to prevent cold air from the twin-leaf cavity entering the slab cores and cooling the interior. However, this wasn't done at the time of construction and is no longer accessible. As a retrofit solution, would it be feasible and effective to drill into the hollowcore slabs from inside the house and fill the first section of the cores with expanding foam to block cold air ingress? Using a stud finder to avoid the prestressed tendons.

10-10-20

This is in a modern construction with insulation in the cavity? What depth of cavity insulation is fitted with what remaining cavity, and is the insulation butted right up against the ends of the hollowcore?

General purpose expanding foam in this situation might be a no-no as it can't be trusted to not push the insulation away from the inner leaf.

Yellow_Fern

https://www.boards.ie/discussion/comment/123530748#Comment_123530748

2016 build. The cavity is a semi semi fill 100mm PIR. I cant see how the PIR is at the level of hollow core hollowcore but when I saw it in exposed window reveals, I could see there was a steady draft between it and the inner leaf. I hadn't thought of the expanding foam blowing out the PIR board but it's a good point.

10-10-20

Has pumped cavity insulation been considered/rulled-out?

The scenario I suggested above probably isn't likely anyway unless the void is completely overfilled, it's at least a 100mm distance from the internal side of the inner leaf anyway. Maybe play around with mock-up tubes to see what fill distance you get from a ~2 second blast of foam?