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Differentiating between 1- and 2-component spray foam insulation

In upgrading to spray foam insulation, a contractor must understand the important differences between 1-component and 2-component foams.

In upgrading to spray foam insulation, a contractor must understand the important differences between 1-component and 2-component foams.

Spray foam insulation has well-documented advantages over traditional insulation, such as fiberglass batts and rolls. It is airtight, can expand to fill a given space, has minimal degradation over time and helps prevent mildew and mold buildup.

With that said, choosing the right type of spray foam can be a confusing process. The most important distinction to make is between 1-component foam and 2-component foam, which have various differences including properties, yields and purposes.

The variety of insulation needed depends greatly on the type of project for which it will be used.

One-component insulation is best used as an insulating caulk for joints and cracks roughly the size of your finger. Gaps around windows, doors or outlets can be addressed with 1-component foam. The material is dispensed in a bead and is suitable for fissures of an inch or less.

Two-component is ideal for filling voids and cavities that are bigger than your fist. Holes, walls and other hollow spaces require this type of foam. It is distributed in the form of a spray pattern that expands rapidly as soon as it leaves the container.

Properties and yields
The two varieties also differ in the way they are measured, the amount they yield, their expansion rate and amount, and their R-value – a measurement of insulation strength.

One-component foam is measured by linear feet, indicated on the side of each container. The total feet will vary based on the volume of the bead when applied. Once applied, the sealant expands only two to three times the dispensed volume in about 5 minutes, depending on the surrounding air temperature and humidity. The R-value of 1-component foam is 4 to 5 per inch once cured.

Two-component foam yield is measured in either board or cubic feet. (A board foot is equal to 12 inches by 12 inches by one inch.) For example, spray foam insulation kits containing 605 board feet yield 50 cubic feet of foam. Once the product is applied, it will expand up to five-six times its original volume in 60 seconds or less. The mixture of the two components causes expansion, not the air. When cured, the R-value is 6 to 7 per inch.

One-component foam comes in dispensing cans and cylinders, with the option of a collar to fit on a dispensing gun for more precise metering.

Two-component systems always have two cylinders. The two chemicals are separate until they hit the dispensing nozzle, at which point the mix together to create the form spray.

Other confusion
One major source of uncertainty regarding the two types of spray foams comes from the term 'low pressure.' Both varieties use this wording to describe two different functions.

For 1-component insulation, low pressure refers to slow expansion or 'slow build.' The foam sets over a longer period of time, relieving pressure against window and door jambs. Excessive pressure can warp these areas, so the slower building foam diverts pressure toward the path of least resistance.

On the other hand, low pressure is used with 2-component insulation to describe the speed at which the foam is dispensed. Low pressure systems have less overspray than high pressure systems. The latter is subject to stringent regulations from the EPA when used in confined areas.

The average person is unaware of the amount of variety involved in spray foam insulation, but it is essential to understand the differences between 1-component and 2-component when planning for a project.