The floor area in a building is one of the most important in a structure to insulate, especially in extreme climatic conditions. Floor insulation helps reduce heat transfer between the interior space and the ground below, enhancing thermal efficiency. It further contributes to maintaining a comfortable indoor temperature, lowering heating and cooling costs, and improving overall energy efficiency in a structure.

 

Asset Score Report Recommendation: Add Floor Insulation

Cost: $$

 

The choice and quantity of insulation to enhance performance depends on the existing floor type. Numerous insulation options are available, and the selection should align with the specific conditions of the existing floors. For floors with a crawlspace, it's advised to add insulation between the floor joists at the top of the crawlspace. Aim to meet the minimum insulation level for your climate, which may be up to R-30 or R-38 in certain cases. It's important to keep in mind, ASHRAE 90.1 2022 do not require floors to be insulated in warmer climate zones since adding floor insulation in those climate conditions can have the opposite effect of increasing energy use. 

For slab-on-grade floors, it's recommended (except for unheated slab-on-grade floors in warmer climate zones) to insulate the perimeter of the slab with rigid insulation, typically at least 1 or 2 inches thick —sometimes more for cost-effectiveness. In unheated basements, apply continuous rigid insulation around the perimeter, extending down to the depth specified in the current building code or to the bottom of the footing, whichever is less. In the case of heated basements, employ continuous rigid insulation around the perimeter of the slab, extending down to the depth stipulated in the current code or to the frost line, whichever is deeper. ASHRAE 90.1 2022 recommends R-20 for 24 or 48 inches in colder climate zones.

 

Resources: 


  1. https://www1.eere.energy.gov/buildings/publications/pdfs/building_america/slab_edge_insulation.pdf
  2. https://bsesc.energy.gov/energy-basics/slab-edge-insulation