Spray Foam R-Values and Performance
Spray foam is more than just insulation: it can also be an air barrier and a vapor retarder. This multi-purpose building material has many performance properties. There are different types of spray foam, and each provides unique benefits. As consumers and building codes demand more energy efficient homes, spray foam products continue to meet and exceed expected energy performance.
Keep in mind that R-value* alone does not fully express the benefits of spray foam insulation. Unlike other forms of insulation, spray foam can form an air barrier without the use of additional products. Air sealing a home, in addition to maximizing R-value, will further improve energy performance.
The chart below shows a few of the performance properties of each type of spray foam.
R-Values and Performance
Low Density or Open Cell Spray Foam | Medium Density or Closed Cell Spray Foam | Closed Cell Roofing Spray Foam |
|
| Thermal Performance: R-Value* | Starting at 3.6 per inch | Starting at 5.7 per inch | Starting at 5.5 per inch |
| 2x4 Cavity: Full Fill | R13 | R20 | Not used for interior application |
| Air Barrier / Sealant | ✓ | ✓ | ✓ |
| Vapor Retarder: Class II rating | ✓ | ✓ |
*R means resistance to heat flow. The higher the R-value, the greater the insulating power. Ask your seller for the fact sheet on R-values.
R-value measures a material’s resistance to heat transfer. Higher R-values mean that the material is more resistant to heat passing through it, making the material a better insulator. R-values are often listed at 1-inch depth for ease of comparing insulation products. To find out the R-value for a specific insulation, refer to the product’s label or technical data sheets, often available online.
SPF products provide a variety of R-values to meet a multitude of performance requirements. For example, different parts of the home or building benefit from different insulation R-values and local energy codes require different R-values for different climates. All three types of SPF can satisfy the R-value requirement for: walls, floors, ceilings, and roofs in every climate. SPF can also go far beyond code for super-insulated structures, vastly exceeding minimum code requirements.
Air Barriers & Permeability
Spray foam is also an air barrier, meaning it resists airflow between conditioned and unconditioned spaces. Air barriers are important considerations in building science because they can improve insulation performance and indoor air quality.
Ever wonder why leaving the refrigerator door or the top of your freezer open significantly decreases its performance? The refrigerator or freezer materials have not changed, but now you have introduced air flow into the equation. As warm air moves into a cold refrigerator or freezer, it has the same effect as warm air moving into an air-conditioned home or building. The air flow impacts the climate, both inside your refrigerator and inside a building.
Air barriers also help keep pollen, dust, insects and other allergens from entering the home or building through cracks or crevices in the wall assemblies. Spray foam adheres to the walls, boards and studs of your home, creating tight seal that limits potential intrusions.
Vapor Retarder
Closed cell spray foam often qualifies as a Class II vapor retarder, as defined by the International Residential Code. A vapor retarder works to prevent moisture (water vapor) from easily passing through the building material. Good building design and practices include controlling the movement of moisture inside and outside a home or building. Excessive moisture inside a building can facilitate mold growth and degrade building or home performance and building material service life.
Ask your SPF contractor for more information about R-value and total building performance.