Below-Grade & Perimeter Foundation Insulation

The Foundation for Below-Grade Moisture Resistance.

With a large offering of below grade and under-slab insulating products, Insulfoam and R-Tech® brand expanded polystyrene (EPS) and graphite polystyrene (GPS) insulation products are engineered to stand the test of time. Designed to insulate concrete, foundation walls or slab while offering the ability to protect waterproofing or damp proofing (especially during back filling), Insulfoam Below Grade Foundation Insulation is widely used for both commercial and residential applications, including:

  • Below-Grade
  • Under Slab
  • Perimeter Insulation
  • Waterproofing Protection Barrier
  • Plaza Decks
  • Block Outs
  • Concrete Forms
  • Landscape & Void Fill
  • Cold Storage
  • Drainage Board
  • Radiant Heated Floors
  • Stadium Seating

Why Insulate Below-Grade?

It’s simple. Below-grade insulation is important both for the longevity of your structures and for the earth. Lack of foundation insulation on below-grade and under slab projects can account for up to 25% of a structure’s total heat loss.  Insulating properly below-grade, can also combat heat loss and help each structure reduce heating and cooling bills by 10-20%.


Standard Insulfoam Below Grade InsulationInsulGrade Soil Loads

Available in custom sized panels and blocks, for ease of material handling. Available in widths up to 4′, lengths up to 16′ and thicknesses up to 40″, InsulGrade is also available in nominal compressive strengths of 10-60 psi. Customize properties to make Insulfoam products suitable for your precise project needs.

R-Tech Insulation, Including Fanfold Bundles

InsulGrade DetailR-Tech features a premium factory-applied polymeric facer that is virtually impervious to moisture, helps keep water from entering the insulation and away from concrete and slabs. Available in 4’x8′ panels, thicknesses starting at 3/8″, with compressive strengths from 10-60 psi, contractors can pick the right thickness and compressive strength for each job. For reduced labor choose R-Tech fanfold protection board,available in lightweight 200 sq. ft. bundles available in thicknesses of 38″, 1/2″, and 3/4″.

InsulGrade UnderSlab Detail

Insulfoam DB – Drainage Board

Manufactured from any standard Insulfoam product, DB’s factory-applied channels and filtration facers help drain and reduce hydrostatic pressure. Available in thicknesses up to 5″.


Why are Insulfoam below-grade insulation products the best choice?

Insulfoam EPS  & GPS outperforms XPS below-grade insulation for less material cost! Consider these three criteria and you’ll agree that Insulfoam is the best insulation choice for your project:

  1. Moisture Absorption: Field studies prove that EPS absorbs less moisture than XPS in the long term.
  2. R-Value Stability: With the highest R-value per dollar, EPS R-Value doesn’t degrade over time. This is why Insulfoam warrants 100% of R-Value, even during freeze-thaw cycles.  XPS only warrants up to 90% of its R-value, and the warranty is regularly void in the case of water ponding or immersion (critical for below-grade applications).
  3. Compressive Strength: Seven standard compressive strengths available, for up to 40% material cost reduction over XPS.

Learn more…


Below Grade Insulation Overview 

InsulFoam® Insulation Products

Alaska Only Below Grade Insulation Products

Data Sheets

Standard InsulFoam® Below Grade EPS Insulation


Platinum GPS Insulation:


R-Tech Insulations
® EPS with laminated polymeric facers


R-Tech Platinum GPS Insulation:

Installation Information

Below-Grade Installation Guidelines

Want to know more?

  • Check out the many Documents available to get specific data for your upcoming projects
  • View our online learning center for training and education resources
  • Browse through our detailed project profiles and photo galleries
  • Request an AIA certified presentation
  • View installation and overview videos
  • or simply take a look through an impressive collaboration of industry news articles about Insulfoam

You can always contact us or find a Representative near you. We are here to help make your insulation selection process easier!