Floors: example of slab laid on soil

Concrete slab

Although roofs are one of the largest sources of heat loss, floors are also significant contributors (between 5% and 10% ). So insulating floors makes homes more comfortable and delivers additional energy savings.

When insulating a floor, the first thing to determine is its configuration. Is it above a cellar, unheated space or crawlspace, or does it sit on soil? Where the floor slab is laid on soil, the relevant installation reference documents are NF DTU 13.3 part 3 for individual homes, and parts 1 and 2 for other types of building.

To withstand the crushing load imposed by the concrete slab, these DTUs (Unified Technical Documents) require the use of insulation products providing a minimum level of mechanical performance, which can be found on the ACERMI certificate for the product, the modulus of elasticity (Es), which is defined as the ratio between two certified characteristics:

Modulus of elasticity (Es)

Label close-up
  • The Es value must always be above 2.1 MPa (MegaPascals), regardless of circumstances
  • For buildings other than individual homes, the thickness of insulation is also limited such that: e (in meters) ≤ Es/50
  • Lastly, the recommendation for this application is to use non-absorbent insulating products meeting a minimum level of mechanical stiffness; characteristics met by products certified as class O2 and L2 in the ISOLE classification

ISOL classification:

  • I: mechanical properties under the effects of compression
  • S: resistance to differential movements
  • O: water resistance
  • L: mechanical properties for cohesion and bending