Feedback on the insulation on the underside of low floors under renovation

It presents 12 major lessons from observations observed in the field and the analysis of experts in the field. This report is made available to all stakeholders in the renovation operations.

Low floors, horizontal walls of which only the upper faces overlook a heated room, can represent significant heat losses and a source of discomfort for the occupants. Insulating them is an action frequently considered during an energy renovation, especially when they overlook cellars, parking lots or open spaces that are easily accessible.

The 12 main lessons learned

The 12 lessons detailed in this report demonstrate the importance of choosing the insulation solution according to the building configuration. Low floors, horizontal walls of which only the upper faces overlook a heated room, can represent significant heat losses and a source of discomfort for the occupants.

These lessons also tell us how to carry out a precise diagnosis of the existing situation before any insulation intervention on the underside of a low floor. This diagnosis is necessary in order to identify and deal with any proven humidity problem upstream of the insulation work, to ensure the good structural condition of the floor to be insulated and to be able to choose an insulation suitable for the hygrothermal conditions of the building. unheated volume.

• Lesson 1: Take care of the junction between insulating panels.
• Lesson 2: Limit the thermal bridge to the low floor - exterior wall connection when these are insulated from the outside.
• Lesson 3: Insulate the beams in contact with the floor to be insulated.
• Lesson 4: Treat the thermal bridge at the level of the cross walls.
• Lesson 5: Isolate access between heated and unheated spaces.
• Lesson 6: Guarantee continuity of insulation over the entire surface of the slab while maintaining access to the premises.
• Lesson 7: Free up the support as much as possible before any intervention.
• Lesson 8: Guarantee access to the operating devices of the networks trapped by the insulation.
• Lesson 9: Take care of the insulation around network penetrations.
• Lesson 10: Maintain the capacity for water vapor migration through the wall.
• Lesson 11: Maintain good ventilation.
• Lesson 12: Take all the necessary measures with regard to the fire risk.

To download the report, click here