Foam insulation gets thumbs up
Oct. 14, 2006 12:00 AM posted in the Arizona Republic
Anyone who knows me well knows that I believe you can't beat a foam roof. I feel the same way about foam insulation for block homes. This dry resin is designed for cavities of concrete masonry and is cost-effective, as opposed to foam block homes covered with half an inch of cement plaster. Exterior walls with little or no insulation can have the foam quickly and easily injected. Even if the home interior is framed and insulated, you will be amazed at the difference in utility bills with the addition of block insulation. When the foam has cured, your home's walls can go from an R-2 to an R-11. The pre-expanded foam is sprayed in through small holes drilled into the wall and fills in all nooks and voids to boost the R-value. This product is also environmentally green, non-toxic and odor-free, with a Class A fire rating.
Typically, foam insulation pays for itself in three years, with the expected energy savings of more than $500 per year. Even better, installation of spray foam block insulation can take less than a day. In addition to insulation value, foam also acts as an acoustical barrier for homeowners near a busy street or noisy neighbors. Insulation acts as a barrier to block outdoor temperatures and to contain indoor temperatures. The higher the R-value of the insulation, the slower the temperatures from either side are able to move through the material.
What is the difference between open-cell and closed-cell polyurethane foams?
This may be one of the most important pages on the website if your interest is in spray foam insulation. When it comes time to actually put the foam product in your home or commercial building structure, you must identify whether you will use .05 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 weaker or softer feeling than closed-cell foam. Closed-cell foam differs in that all of its tiny foam cells are closed and packed together. They are filled with a gas that helps the foam rise and expand and become a greater insulator. These cells can be formulated to obtain many characteristics, the most common being size and density. Density is measured by weighing one solid cubic foot of foam material. Open cell foams typically weigh in at .05 lb./cu. ft. Closed cell foam for insulation applications range in density from 1.7 lb./cu. ft. to 2.0 lb./cu. ft. Roofing applications typically use a 3.0 lb./cu. ft. to support traffic and loads better. The higher the density the foam, the heavier, or stronger it becomes. Some polyurethane foams are molded into decorative interior molding and painted or stained for a simulated wood effect. These “higher density” foams are typically in the 30 lb./cu. ft. to 40 lb./cu. ft. density range. 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, 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 foam would be a good choice where small framing sizes need the greatest R-value per inch possible. Closed-cell foam would be used for roofing applications.
SPF Out Performs Fiberglass:In Attic Insulation Performance Tests at Oak idge National
Laboratories For years SPF contractors have been frustrated by prescriptive building code requirements that mandated extremely high R-values in attics, particularly in cold climates. For example in Wisconsin, R-values of 49 are prescribed in attics. In order to provide more realistic evaluations of insulation systems, Oak Ridge National Laboratories developed a large scale, attic climate simulator that could provide data on how efficiently insulation systems rated R-values matched up to more real life performance.
NIST Report Favorable Towards Spray Foam Roofing:The National Institute for Standards and Technology (NIST) located in Gathersburg, MD recently released a report stating the impacts from hurricanes Katrina and Rita on structures in the damaged areas. SPFA is extremely excited to announce that this report is extremely favorable towards spray foam roofing. The reports stated that spray foam roofs were the only type of roofing system that was described as having performed “extremely well” by NIST officials. Other sections of the report
describe how spray foam roofing withstood Hurricane Katrina’s winds without blow-off or damage to the flashings. The Spray Polyurethane Foam Alliance (SPFA) is very excited to alert the industry to these finding and be a part of this outstanding achievement in the industry.
SPFA proposes code changes to ICC:A volunteer task group drawn from SPFA's Technical, Building Envelope, Low Density, and Steering Committees identified and proposed three code changes to the International Code Congress on March 24. The three items include: Allow the use of SPF roofing systems over existing asphalt shingle, clay tile, and concrete tile roofing systems. The use of SPF over these roofing systems in high wind areas has been documented with recent roof damage investigations from hurricanes Charley, Ivan, and Katrina. In all cases, the SPF roofing systems performed exceptionally well and in some cases reduced further damage to the roof structure and interior of the buildings. Allow the use of SPF as insulation in ducts located in attics and crawl spaces of buildings. SPF seals, as well as insulates and the use of SPF over ducts is a safety enhancement. Using SPF to seal the cracks and crevices commonly found in ducts could cut down on the risk of smoke spreading throughout the building during a fire. Require the use of air barriers in commercial buildings. According to Department of Energy studies, unwanted air infiltration and exfiltration account for more than 10 to 40% energy loss in buildings. Requiring the use of air barriers in commercial buildings would greatly reduce the amount of air leakage. SPF is one of the premier products that can effectively control unwanted air movement in buildings.
The R-value Myth and the advantage of SPF insulation
One great Myth of modern home construction is the "R-value" measurement used for insulation. R-values have been peddled to consumers for so long they have taken on
"Chiseled-In-Stone" status. The saddest part of this myth is that the R-value by itself is almost a worthless number, as it is impossible to define insulation effectiveness by this number alone. So why is the R-value myth perpetuated? I don't know if anybody knows. It obviously favors fiber insulations manufactured by Huge International Corporations, who regularly contribute to political campaigns.
What would the R-value of insulation be after it has been submersed in water or had a 20 mile per hour wind blowing through it? Obviously the "Effective" R-value of fiber insulation would go to zero, but Spray Foam Insulation would be largely unaffected. Again, R-valuesare "funny" numbers; they are meaningless unless we know the other important factors.
The use of R-values as the only criteria is absolutely ridiculous, yet we have Government
Agencies mandating R-values in the 20's, 30's and 40's today. Fiber insulation having an R-25-value installed in a house, but not properly sealed will allow the wind to travel through it as if there were no insulation at all.
R-values are a result testing the flow of heat through material in a sealed test fixture under controlled laboratory conditions, but these conditions are not even remotely associated with the real world installed performance of insulation. To calculate the actual installed performance of insulation, we also need to know its resistance to air penetration, to internal air currents, to liquid water, and to water vapor drive. What really matters is the "effective" R-value when insulation is subjected to these real world conditions?
Fiber insulation is generally assigned an R-value of approximately 3.5 per inch, yet it can only achieve this value when tested in an absolute zero air-movement and zero moisture environments. Zero wind and zero moisture are not real-world conditions, as all homes leak air and they sometimes leak water. In addition, water vapor from the atmosphere, showers, cooking, breathing, etc. constantly moves back and forth through the walls and ceilings of our homes.
If an attic is not properly ventilated on a fiber insulated home, the water vapor generated inside a house will very quickly semi-saturate the insulation above the ceiling and in the walls. Even small amounts of moisture will cause a dramatic drop, as much as 50 percent or more, in fiber insulation's performance.
Vapor Barriers
Because such small amounts of moisture have devastating effects on fiber insulations
performance, it is recommended that fiber insulation have a vapor barrier installed on the warm side of the insulation. This recommendation poses a completely new problem, which is the warm side of the wall? Obviously, the warm side changes from summer to winter, even from day to night. If it is 30 degrees outside, the inside of an occupied house is certainly the warm side, conversely, during the summer months, when the sun is shining; the warm side is the outside of the wall. Occasionally, a novice will try to put vapor barriers on both sides of the insulation, but this proves to be disastrous because the vapor barriers will stop most of the moisture but not all. Small amounts of moisture will still move into the fiber insulation between the two vapor barriers and become trapped. It will accumulate as the temperature swings back and forth altering the direction of vapor drive forces, leading to significant mold growth, health problems, building rot and increased energy costs. Fiber insulation must be ventilated on one side or you can end up with serious mold growth problems, as illustrated in these images. This required ventilation also allows air movement within the fiber insulation, significantly reducing its effectiveness. Spray Foam Insulation does not have these limitations. It creates its own air-tight seal, while still allowing water vapor to pass through without accumulating or affecting its performance.
Air Currents Within Fiber Insulation
We all understand air penetration through the walls of our homes; we can even feel it in some homes when the wind blows. But what most people, including many engineers, do not realize is that there are very significant convection currents occurring within the traditional insulations. These convection currents rotate vast amounts of air, leading to significant energy losses.
These convective air currents are not fast enough to feel and are difficult to measure without sensitive instruments. Nevertheless, these air current are constantly carrying heat from the bottom of the fiber insulation to the top side, letting it escape.
If we seal off this air movement with traditional insulation, we seal in the water vapor where it will condense into a liquid becoming a source of moisture for mold growth and rotting of your home. This water vapor and resulting condensation will also seriously decrease the fiber insulation's R-value and increase your energy costs. The only way to deal with fiber insulation is to ventilate, but to ventilate means allowing air movement, which decreases the R-value and increases your energy costs.
Once again, Spray Foam Insulation does not have these limitations, because it creates its own air-tight seal, while still allowing water vapor to pass through without accumulating or affecting its performance.
