A building’s foundation comes in direct contact with the elements. It’s the first part of your structure to feel the effects of the freeze-thaw cycle. Without a sturdy foundation, a building will eventually crumble. One way to protect your foundation is by insulating it with continuous basement wall insulation.
What is Continuous Insulation?
Continuous insulation is an installation method in construction that refers to insulation that goes uninterrupted over the entire surface area of the building envelope. For example, insulation inside a wall cavity (stud wall insulation) is not continuous because it is interrupted by inch and a half thick studs every sixteen inches or so. In order to be continuous, the insulation must be its full thickness over the entire wall or other surface being covered.
Typically, continuous insulation is installed on the outside of the structure to fully encapsulate the envelope. This includes the exterior side of perimeter walls, basement walls, foundations, and roof decks. Sometimes multiple layers of insulation are used to achieve the desired R-value. Building codes usually determine continuous insulation R-value requirements for each part of the building envelope.
How Much Basement Wall Insulation is Required?
A building’s location will determine how much basement wall insulation is required by code. In commercial construction, the IECC code calls for continuous R-values for basement wall insulation below grade.
Code Requirements for Basement Wall Insulation
So, how do these R-value requirements convert to actual insulation thickness requirements? Let’s say your local building code calls for R15 continuous insulation on walls. If you choose polyiso, you can achieve R15 with just 2-½” thick polyiso material such as Rmax Durasheath® building envelope insulation. If you use extruded polystyrene insulation, it will require 3” thick XPS boards and for EPS, it would take nearly 4” thickness, depending on the density.
Why Use Continuous Insulation at Basement Walls?
Now that we’ve covered what continuous insulation is and how much is required at basement walls, let’s move on to why you need it in the first place. Here are the benefits of using continuous insulation on your basement walls
Prevents Mold
Keeps Floors Warmer
Protects Foundation Walls
Reduces Energy Bills
Creates a Moisture Barrier
Eliminates Condensation
Since basements are prone to moisture problems, it’s a critical spot to pay attention to during the design phase of a new construction project. Spend some time designing a basement wall section that incorporates a vapor barrier to keep moisture out and a vapor barrier to protect against condensation.
Lastly, the basement level of buildings can sometimes feel cold rather than comfortable. By adding continuous insulation to basement walls, you can increase thermal comfort in the lower level of a building while also saving on energy costs.
How to Install Basement Wall Insulation
Basement wall insulation is typically installed on the outside of your foundation, against the basement waterproofing system, and then backfilled with soil. The standard installation goes in three steps:
Excavate to expose the basement walls.
Install waterproofing or dampproofing system, including drainage mat.
Install basement wall insulation to protect waterproofing.
When installing basement wall insulation on the exterior, you can use tack adhesive or fasteners to hold boards in place until backfilled with soil. Optionally, you may also opt for taping the joints with compatible pressure sensitive sealing tape.
There are occasions when insulation is installed on the interior side of basement walls rather than the exterior. While this assembly provides less freeze-thaw protection for your foundation, it is an option whenever excavation is not on the table.
Choosing the Right Insulation
As you shop for basement wall insulation, look for materials that are made of inorganic materials so that mold growth is inhibited. Other factors to look for in quality below-grade insulation include:
Polyiso foam board insulation like Rmax Thermasheath® is made with durable reinforced aluminum facers that meet all of the criteria above, to boost your building's performance for basement wall applications.
Turn to the Insulation Experts at Rmax
Rmax has been manufacturing insulation for decades. If you’re shopping for basement wall insulation, you can trust the folks at Rmax to help set your project up for success.
Reach out today to talk about your project needs!