RAISE YOUR EXPECTATIONS OF
BELOW-GRADE INSULATION

RMAX® BELOW GRADE INSULATION FOR EXTERIOR WALL AND FOUNDATION

Did you know it’s a best practice in construction to insulate the entire building envelope? This includes all exterior walls, roof or attic spaces, and even your flooring and foundation. Any barrier that separates your building from the outside should be insulated, even underground.

What is Below-Grade Exterior Insulation?

Below-grade exterior insulation is installed below ground level on the exterior facing side of the building envelope. It is designed to come in direct contact with soil, water, and the earth. You’ll find below-grade insulation on the exterior side of the foundation or basement walls and under slabs.

Why You Need Below-Grade Insulation

Since below-grade insulation cannot be easily replaced during a renovation without excavating your project’s site, it’s critical to understand the importance of installing below-grade insulation during the initial construction phase. Here are some of the reasons why you need below-grade insulation:

Waterproofing Protection

You always want to protect your lower level with waterproofing or dampproofing to keep water out. Most waterproofing systems require a protection layer. Below-grade insulation protects the system from backfill damage.

Thermal Efficiency

Insulation minimizes heat loss through your building envelope. That means that it helps to keep the heat out in the summer and the heat inside your space in the winter. By installing below-grade insulation at your foundation or below your slab, you can reduce heat loss that occurs below ground level while increasing the efficiency of your heating and air conditioning efforts.

Moisture Control

Below-grade insulation can help with moisture control by reducing condensation potential. Condensation occurs when warm, moist air hits a cold surface. By using below-grade insulation on your foundation walls, you can reduce the temperature variation and thus reduce the risk of condensation on the inside of the walls.

Freeze-Thaw

Another reason that below grade insulation is an important component of your building envelope is for protection of your structure against the freeze-thaw cycle. This cycle occurs naturally as temperatures change throughout the year. Some consequences of freeze-thaw are frost heave (shifting of the building) and water migration/freezing (cracks in concrete). Keep the wall warm and reduce the impact of the freeze-thaw cycle on your structural components by separating them from the earth with a layer of below-grade insulation.

Below-Grade Insulation Products

When it comes to choosing the right below-grade insulation, you’ll have a few choices. Common types of insulation used in below-grade applications include extruded polystyrene (XPS), expanded polystyrene (EPS), and polyiso. Check out our full comparison of XPS, EPS, and polyiso.

There are many advantages to using board insulation for below-grade applications, including:

• Dual purpose that provides physical protection and thermal efficiency

• Easy to install continuous insulation

• No reduction in useable interior space

Rmax® below grade

Rmax® Below Grade is a versatile polyiso insulation that is used throughout the entire building envelope, including in below-grade concrete foundation wall applications to protect waterproofing systems and meet energy code requirements. Made with durable and resilient facers, it boasts an R-value of R10 at only 1.5” and can be installed vertically or horizontally in a continuous manner.

When choosing a below-grade insulation, it’s important to look at water absorption and vapor permeance performance. Polyiso provides superior water vapor permeance protection.

How Rmax® Can Help

If you’re ready to choose your below-grade insulation for your project, Rmax® can help! Let our representatives take a look at your project and suggest the insulation that will meet your design criteria and keep your building comfortable.

Reach out to your local Rmax® representative today.