R-Value measures a material’s resistance to heat flow.
R-Value was invented to measure fiberglass insulation. In the late ’50s, when insulation became code to be installed in our homes, fiberglass insulation was the only insulation available. In return, R-Value was established to measure the fiberglass resistance to heat flow.
In order to better explain why R-Value was established for fiberglass, we need to look at the definition of R-Value and the three heat transfers that happen on any building or structure.
The Three Types of Heat Transfer:
Fiberglass insulation only reduces one of the three heat transfers- conduction. It does not stop convection or radiation.
Spray foam insulation stops or controls all three of the heat transfers that occur on any building or structure. This is what makes spray foam insulation so effective by saving up to 50% on monthly utility bills, better indoor air quality as well as its ability to never shrink or settle.
Spray foam is installed to underside of the roof in the attic for most attic applications. We will remove your old insulation, then spray foam is installed to the underside of roofdeck. This allows for attic to be used as storage space, future wiring can be installed as needed throughout the attic without competing with blown insulation to dig into, this also protects your HVAC system as ducts are then enclosed in a better environment for operation. Make sure to talk with your HVAC company reguarding the different needs for homes that use spray foam insulation vs. fiberglass.
When it comes time to actually put the foam product in your home or commercial building structure, you must identify whether you will use 0.5 lb./cu. ft., open cell foam, or 2.0 lb./cu. ft. closed cell foam. This makes a big difference in cost, application methods, and performance.
With the open-cell vs. closed-cell issue, there are two major factors to understand and consider. The first is the nature of the foam. It is either open-cell foam, where the tiny cells of the foam are not completely closed. They are broken and air fills all of the “open” space inside the material. This makes the foam softer feeling than closed-cell foam.
Closed-cell foam differs in that all of its tiny foam cells are closed and packed together.
Density is measured by weighing one solid cubic foot of foam material
The advantages of closed-cell foam compared to open-cell foam include its strength, higher R-value, and its greater resistance to the leakage of air or water vapor. The disadvantage of the closed-cell foam is that it is denser, requires more material, and therefore, is more expensive. Even though it has a better R-value, typically the cost per R is still higher than open-cell foam. The choice of foam can also be based on the requirements for the other performance or application specific characteristics such as strength, vapor control, available space, location of installation, etc.
Both types of foam are commonly used in most building applications and the choice for which to use can depend on many of the factors discussed above. Some foams are inappropriate in specific applications. For example, you typically would not use open-cell foam below grade or in flotation applications where it could absorb water; this would negate its thermal performance because water is a poor insulator compared to air.
Closed cell spray foam is best used in ground floors, wine cellars, and masonry walls.
Open cell spray foam is best used on roofdecks, interior, and exterior walls.
