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Spray Foam Facts

Many people have only recently become aware of spray applied polyurethane foam and there is currently a great deal of misunderstanding concerning its properties and use. Many people don’t realize that there are different kinds of spray foam and many different uses for each of those kinds. The variety of uses possible with polyurethane foams has gained greater awareness among the general public, but mis-conceptions, inaccurate information, and rumors abound.

We would like to expose some of those rumors, explain some of the basic properties of polyurethane foam, and make you aware of some of the fascinating things that polyurethane foams can do for the construction industry.

We will discuss the following types and applications:

1. Closed-cell interior wall foam

2. Open-cell interior wall foam

3. Pour foam

4. Lifting foam

5. Roofing foam

6. Can foam

7. Injected foam

Closed cell foam was developed in the early 1940’s and by definition must have a closed cell content greater than 90% and a density greater than 1.5 lbs per.cu.ft. Most interior applications for closed cell spray foam are 1.7 to 2.0 lb. products with an R-value of 6.5-7.4 per inch.

Closed-Cell foam offers the highest R-value per inch of any commonly used insulation material. It also provides a seamless air barrier at 1” and it provides a Class 2 vapor barrier at 1.25”, depending on the brand of foam used.

Due to the strong adhesive and cohesive nature of Closed Cell foam, installing 2 inches of closed cell spray foam in a 2×4 wall increases the racking strength 200% to 300%.- NAHB  This is a significant advantage that only Closed Cell Spray foam can offer, and there are numerous examples of structures with closed cell foam insulation outperforming neighboring buildings during severe weather.- Honeywell (pgs 9,11,12)  This quality in closed cell foam is very beneficial especially when used in steel buildings. Steel buildings are prone to damage from high winds and can be very drafty, but with a closed cell foam insulation system the entire structure is essentially glued together with 2 or more inches of insulating, sound deadening, air-sealing, energy saving foam that greatly reduces the potential for damage from high winds or rainwater penetration into the building.

Closed Cell Foam is the only insulation material approved by FEMA for buildings in a flood zone. This is because closed cell foam is so durable and moisture resistant that it can be subjected to flood waters for over 72 hours without permanent damage. It can be cleaned by rinsing with water without any need for replacement.

Closed cell Foam is required by Local Building codes to have a 15 min. thermal barrier covering such as ½” gypsum board, when used in residential and commercial living spaces. However it can be used as a stand alone system without additional fire protection when used in attics and crawlspaces. Because closed cell foam offers a complete air seal, it should not be used in dwellings without Heat Recovery Ventilation systems or indoor air quality can be poor.

For more information about closed cell foam visit, ccfoam.com.

Next on our list is Open-Cell foam.

Open Cell Foam was developed in the early 1990’s and has a density of .5 lbs. per. cu. ft. and an R-value of 3.2-4.2 per inch.

Open-cell foam’s lower R-value per inch is offset by a lower cost per inch which allows builders to achieve an R-20 at 5 inches of open cell foam for roughly the same price as it would cost to achieve an R-13 using 2 inches of closed cell foam.

Open Cell foam provides an air barrier at 3.5 inches. This is significant because the bulk of moisture transfer and energy loss through a building envelope is air carried. By eliminating air flow we reduce the ability of moisture to move through the wall and condense on any cold surfaces. However, open cell foam is not a vapor barrier and is still vulnerable to vapor drive. Vapor drive comes into play when there is a strong vapor drive in one direction such as in a room with a swimming pool or sauna or a walk-in-freezer. In these environments, open cell foam can become saturated with moisture and will perform at greatly reduced efficiencies. Open cell is not suitable for applications with a significant vapor drive in one direction.

Open Cell foam requires a 15 min. thermal barrier when used in residential and commercial buildings except in attics where a 15 min. ignition barrier is accepted in place of a thermal barrier. Because open cell foam offers a complete air seal, it should not be used in dwellings without Heat Recovery Ventilators or Indoor Air Quality will be negatively affected.

Open cell foam does not increase the structural strength of a building.

Which is better? Open cell or Closed cell?  Clearly, closed cell is better because of its superior vapor protection, strength, higher R-value per inch, and its superior resistance to fire and flood damage, but open cell is a close second because it offers an air tight seal and it offers an R-20 for roughly the same price as an R-13 with closed cell. There is a never ending debate in the spray foam industry about which foam is a better value, but ultimately it’s up to the customer to decide whether they want Closed Cell or Open cell, and it’s up to the Spray foam contractor to provide accurate information to enable the buyer to make an informed decision. DeFord Insulating Company sprays both open and closed cell foams and we are more than happy to make recommendations on which would be best for you based on your specific project.

Pour Foam is made by lowering the reactivity of spray foams so that the foam may be poured into a cavity before it starts to expand. It is used for applications when it is not possible or convenient to spray the substrate. Such applications include but are not limited to:

Filling voids in  cinderblock walls.

Filling floatation chambers in boats and docks.

Filling voids in studded walls.

Pour foam applications have to be managed carefully because the force of expansion as the foam reacts can burst its container or swell the wall cavity.

Lifting Foam is a type of closed cell foam that can be used for repairing roads, bridges, and railways that have been compromised by settling of the soil underneath the structure. It uses the natural force of expansion inherent in all spray foams to generate lift under settled slabs or buildings. Lifting foam is applied by injecting it into the soil underneath the road or slab. As the foam expands, it lifts the cement to bring it to a consistent level with the roadway or structure around it. As much as 4 inches of lift can be gained through this application.

Next in our discussion is Roofing Foam. Roofing foam is yet another type of closed cell foam with a density of 2.5-3.5 lbs. per cu.ft. and an R-value near 7 per inch. It is durable enough to endure foot traffic and not only provides a long-lasting durable roof, but also a high performance insulation system that pays for itself over time. – TA&M Case Study Because sunlight deteriorates foam over time, roofing foam must be coated with UV protective coatings and must be recoated every 10 to 30 years depending on the type of coating used. Properly maintained, foam roofing systems can last a lifetime. – Honeywell (pg. 17)

Foam can also be packaged in cans and is used for sealing around windows and doors and other building envelope penetrations. There are many different types of can foam on the market today and they are available in both high expansion and low expansion versions.

Last of all is Injected foam. Even though injected foams are not in the polyurethane family of foams, we’ve included them here because many people associate injected foam with spray foam.

Injected foam is a phenolics or polymer based chemical system, not a polyurethane system, and its application and chemical makeup is much different than spray foam.. It has a density of .5 lbs. and an R-value of 4.1 to 5.1 per inch. During application it has the consistency of shaving cream and cures to a light, brittle, powdery consistency. This is the type of foam sold by Retrofoam. It is most often used to improve the insulation of existing buildings without removing the wall linings. It does not expand during installation and poses no threat of bursting the wall cavity. After being installed, injected foam shrinks as it dries and can shrink from the edges of a cavity .13” to 4.25.” If injected foam dries too quickly, it can shrink as much as 80%.

When installing injected foam systems, there is  potential for incomplete filling of the cavity due to obstructions in the wall cavity and faulty installation. There is rarely any opportunity to verify that a complete cavity fill has been achieved due to the fact that it is typically installed without opening either side of the wall cavity. In cold climates, the voids resulting from an incomplete cavity fill can become areas of moisture condensation and consequent mold growth. Testing on injected foam systems demonstrating these traits was conducted by Branz, an Australian research group. Click here to view the report.

While there are some disadvantages to injected foam systems, this does not mean that they are without value. In an un-insulated wall or a poorly insulated wall, injected foam can significantly improve the thermal efficiency by up to 50% in spite of its shortcomings.

If you have any questions about injected foam or any of other types of foam we have discussed, please contact us at caleb@defordinsulating.com or call Caleb at 515-371-0858.

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