Understanding Continuous Insulation

What is Continuous Insulation?

Continuous insulation (ci) (as defined in ASHRAE 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings):

“Insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings. It is installed on the interior, exterior, or is integral to any opaque surface of the building envelope.”

Why Continuous Insulation?

Wood and steel studs, joists and other framing members make-up a large portion of any wall, and provide a path for hot or cold air to escape which reduces the energy efficiency of a building. (This heat transfer is also known as “thermal bridging” in the building science community.)  Insulation does not allow the same air transfer as steel and wood framing does, therefore adding a layer of ci over framing (studs and cavities) assists in boosting the thermal performance and energy efficiency of the building envelope. Building owners benefit through reduced heating and cooling energy costs.

Since 2012 the International Energy Conservation Code (IECC) has required continuous insulation in the building envelope in most all Climate Zones (as defined by ASHRAE 90.1). To help improve the energy efficiency of buildings, the IECC has specifically prescribed how much insulation is required for various types of above grade walls, below grade slab & walls, roofs and floors, within each of the 8 U.S. climate zones – for both commercial and residential  buildings.

In addition to enhancing a building’s energy efficiency, CI helps reduce moisture damage in the building envelop by lowering condensation within the envelope assembly resulting from vapor diffusion.

Continuous Insulation Options Using Rigid Foams

The most commonly used CI options are rigid foam insulations:

• Expanded Polystyrene (EPS)
• Graphite Polystyrene (GPS)
• Extruded Polystyrene (XPS)
• Polyisocyanurate (Polyiso)

Among rigid foam insulations, EPS and GPS have the highest R-value per dollar, which makes them well-suited for cost-effective continuous insulation. EPS, such as Insulfoam EPS and R-Tech branded products, is a rigid and tough, closed-cell foam that provides about R 3.9 per inch of thickness for 1# material. Due to the way it is made, unlike other rigid foam insulations, EPS retains its R-Value throughout its time in service. EPS is the most versatile of rigid insulations because it can be used anywhere in the building envelope – roof, walls, floors, and below grade since it dries quickly and assists with moisture management requirements.

Insulfoam’s R-TECH is an engineered rigid insulation consisting of a superior closed-cell, lightweight and resilient EPS with advanced polymeric laminate facers, which provide durability and protect against moisture.

GPS, graphite-infused polystyrene, insulation provides R 5 per nominal inch of thickness. It combines factory laminated metalized polymeric facers and premium insulation into one product.

Mostly used in walls or below grade applications, XPS provides about R 5 per inch of thickness, and is mid-range in price between EPS and ISO. Although XPS is slow to absorb moisture, it is also slow to release it, which can reduce the insulation’s effective R-Value as it retains moisture over time. Most XPS manufacturer warranties reflect this R-Value decline and only warrant 90% or less (warranted percentages also decrease over time) of the product’s thermal value.

Historically polyiso was used in roof assemblies, although some manufacturers now offer wall insulation. Polyiso panels provide up to R 6.5 (aged value) per inch of thickness. Polyiso R-Values start at about R-7 per inch, but (like XPS) degrade over time as the thermal-enhancing blowing agents used to make them diffuse out of the material. Polyiso thermal warranties also reflect this R-Value decline.

Use Insulfoam products to meet CI requirements, build more efficient structures and create comfort

Insulfoam offers its EPS and GPS products in a range of options that easily enable its use to meet increasingly stringent wall insulation requirements. While needing to adapt to new codes, the end result is a more energy efficient structure for the occupants that they'll experience from an energy savings and comfort perspective.