Spray Foam Insulation
When many people think of home insulation, they think of rolls of fiberglass batt insulation, but there are many different types of insulation available. In addition to the traditional fiberglass batts, there are products such as foam board and loose-fill or blown-in fiberglass or cellulose. One of the best insulation products available today is spray foam insulation.
As the name implies, spray foam insulation is polyurethane foam insulation that is sprayed onto the surface where insulation is required. Spray foam provides superior insulation than other types of insulation such as fiberglass or cellulose. There are two main types of spray foam insulation: open cell and closed cell. Both open cell and closed cell spray foam consists of two liquid components, generally referred to as component A and component B, that are mixed together at the job site. The components of the mixture react quickly once sprayed onto the surface where a blowing agent makes it expand to create a polyurethane foam. Because the insulation is a liquid that is sprayed onto the surface, spray foam insulation is able to be applied to hard to reach areas and is able to create a much better seal than traditional foam products. The result is better insulation and lower energy bills.
Open cell foam is low-density and has a spongy texture. The density of open cell foam is around one-half pound per cubic foot and the R-value ranges from 3.5-3.6 per inch, or in a 2 x 4 wall, R-13 or in a 2 x 6 wall or roof deck, R-20. Open cell foam is generally used in above grade residential applications.
Open cell foam provides the following benefits:
- Provides excellent thermal insulation and is air impermeable at wall thickness.
- Absorbs sound very well making it a good choice for sound insulation.
- Good for filling in walls, ceilings, and hard to reach areas due to its expansive properties.
- Less expensive than closed cell foam.
- Uses water as a blowing agent instead of chemicals.
- In an attic application, it seals the attic, the attic becomes conditioned space, making unsightly attic roof vents unnecessary.
When compared to closed cell foam, open cell foam has the following disadvantages:
- Lower R-value than closed cell.
- Absorbs and holds water, which means it should not be used in areas where water can be an issue such as below-grade applications. However, because it absorbs water, open cell foam can identify potential leaks earlier than closed cell.
- Requires a thicker layer to achieve the same R-value as closed cell.
Closed cell foam is medium-density and has rigid texture. The density of closed cell foam is generally around two pounds per cubic foot and the R-value is in the range of 6.5-7 per inch, or in a 2 x 4 wall, R-23, and in a 2 x 6 wall or roof deck R-36.
Closed cell foam provides the following benefits:
- Provides excellent thermal insulation and is air impermeable.
- Considered water resistant making it a good choice for below grade and exterior applications and any area where water can be an issue such as flood prone areas.
- Adds structural strength to walls, ceilings, and roof.
- Can be applied at cold temperatures.
When compared to open cell foam, closed cell foam has the following disadvantages:
- Does not absorb sound as well as open cell foam making it not a good choice for sound insulation.
- Is more expensive than open cell foam.
- Historically, closed cell is higher in HFCs (hydrofluorocarbons) due to the blowing agents generally being chemicals rather than water like in open cell foam. Green builders have stayed away from closed cell for this reason. However, in recent years water has been introduced as a blowing agent for closed cell foam.
While spray foam insulation generally is a better choice when insulating your home versus other insulation products, it requires precise insulation to achieve its maximum effectiveness. Proper mixing of the components and allowing it to get up to temperature before applying is crucial in proper installation.