1/2 lb Foam vs. 2lb Foam

A Guide To Understanding Spray Foam Insulation

When home builders and remodelers hire a contractor to complete their insulation needs, the person hiring the contractor is responsible for ensuring that the degree of insulation benefits being paid for, is the right insulation circumstances for their project needs.

In other words, hiring an insulation contractor by price, both low and high, will not guarantee that the insulation product itself will give satisfactory results unless the shopper knows how various insulation products work. This is like buying a car; all will provide transportation, but some will be more suited to unique customer needs over others.

1/2lb vs 2lb Spray Foam

Spray foam insulation comes in various weights. Common choices in weights will include half-pound or two-pound options ; both have different uses.

Spray polyurethane foam is a substance that can be light and airy like the polyurethane foam used in sofas, or it can be rigid and sealing like the polyurethane hard rubber-like moldings around door frames.

Uses for Both Products

Spray foam insulation normally comes in the common half-pound and two-pound sizes for a reason. Each size is used for a different purpose during the insulation process. The lightweight, ½ lb SPF is used to seal along edges and inside of nooks or crannies While the heavier 2 lb spray foam, which provides a higher R-Value, is used for the bulk of the wall insulation.

• 2 lb. heavyweight SPF is used for insulating walls and floors of your home.
• ½ lb. lightweight SPF is the best choice for just noise insulation, such as in a high school music classroom.

Understanding R-Values

When insulation is added to a building to help control the climate, the ability of the insulation product to keep unwanted climates out is rated in R-Value.

Example:

R1 Factor = a small amount of insulating property.
R5 Factor = 5 times more insulating ability than an R1 rating.

For insulating your home, a qualified insulation contractor can help you determine the proper R-Value needed to insulate your home. The correct R-Value will be determined by your homes heating and cooling system, where you live, and where the insulation is being applied. (For more on this topic, click here.) In the northeast, 2lb spray foam should be used to provide the correct R-Value for your insulation needs.

• ½ lb. lightweight size SPF has an R Factor rating of about 3.5 per one-inch deep layer.
• 2 lb. heavyweight size SPF has an R Factor rating of about 6 per one-inch deep layer.

Understanding SPF Structure

Spray foam insulation (SPF) will expand as it is sprayed, and this gives it the ability to seal cracks and uneven surfaces; the expansion rate happens differently by weight. Heavier SPF will expand less than lighter SPF so that the end results are like two different products: what is often referred to as “open-cell” spray foam and “closed-cell” spray foam. This can be likened to the difference between white bread bread vs. a tortilla. Moisture can easily soak into open cell spray foam, just like it does with white bread. 2lb closed cell foam, or heavyweight SPF, has a hard time absorbing moisture, just like a tortilla. In fact, the US Department of Energy insulation fact sheet (August 1997) notes:

“Spray polyurethane foam alone…can provide an air-and water-tight barrier.”

Shop Smart

Never let a contractor talk you into using a product that is not appropriate to your needs. There are some contractors out there who will attempt to talk clients into completely insulating a dwelling with the lightweight SPF product to save money. But, there is no money saved if the product does not work well, can leave your home susceptible to moisture, and won’t last as long as the product specifically intended for insulating walls.

Fore more detailed information, download this .pdf.