Retrofitting radon sump

First of all check on the link below with your Eircode to ascertain if a Radon Barrier is required for your area.

(Do not have a space in your Eircode)

https://gis.epa.ie/EPAMaps/Radon?lid=EPA:RadonMapforWorkplaces

Some areas do not require a Radon Barrier. The Radon Sump is always required for new works and in renovations, where practical.

That’s a good idea

Is the subfloor existing.

What are the heights of your proposed hardcore and concrete.

See Photos from Homebonds House Building Manual. Are these of any help.

I have never used spray insulation in a floor. Sheet insulation is far mor superior.

The underfloor heating pipes should be in a 50 mm screed, on top of the 100 / 150 mm insulation on top of the 150 mm Concrete subfloor.

See photos

Find the existing horizontal DPC in the existing walls, apply Premium Acrylic Sealant - radon sealing - on to the DPC and push the turn-up of the Radon Barrier DPM on to the Acrylic Sealant, and make sure it is bonded.

Don't be fooled by the sales talk on the TLA. In order to achieve a u-value of 0.15w/m2k you would need about 250mm and that is if the mix is exactly as per test conditions of the certification.