Under Slab Insulation

Can I please get some clarification on what is required for under slab insulation installation? And what does FR5 presume when adding slab to the underside of a slab on ground. Is it required to follow the internal footings/stiffening beams? Or just under the 100mm pad?

TechLink Response:

• A major consideration is that CHENATH calculates 2 dimensional heat flows.
• The edge beams are substantially covered by the external walls especially in masonry veneer designs.
• It is highly unusual for documentation provided to TPAs to illustrate the rib layout for a slab on ground.
• The FR5 Floor Builder Guidance Note does not make any reference to specific treatment of insulation under slab, ribs, or beams.
• Construction practices on site result in much neater rib and beam formation when under floor insulation is used as it minimizes the volume of concrete installed with the commensurate cost benefit.
• The floor builder data entry does not indicate extra concrete thickness for rib and beam areas.
• Accordingly, it is normal TPA practice to have the added insulation value of the proposed insulation applied to the whole slab area of given thickness.