Rate of Outgassing of Foam Insulation; relationship between thermal performance of foam insulation and time degradation
The question-and-answer article below paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.
Polyurethane Foam R-Value Loss Mechanisms
Thank you for an excellent article on building insulation materials (Solar Age, "Building it Right", 11/83, also see our complete guide to insulation at INSULATION INSPECTION & IMPROVEMENT). Of all the areas in the field of energy-efficient materials and construction, none is so fraught with misinformation as insulation.
After many inquiries to manufacturers and extruders of rigid foam insulation products I have been unable to find accurate information as to the rate of outgassing in foam building insulation, or the relationship between thermal performance of foam insulation and time. Have you found any better information than I have? -- Michael Luttrell, Napa CA
Polyurethane foams lose R-value by two mechanisms: air infiltrating the foam and fluorocarbon gas diffusing out of the foam insulation.
Immediately after manufacture, polyurethane foam increases in conductivity quite rapidly. The rate of increase in foam insulating board conductivity (which is equivalent to a loss in the foam insulating board's R-value) ultimately stabilizes at a plateau level, which can remain unchanged after more than 10 years.
Since most of the change in foam insulating board R-value occurs in the first two to two-and-a-half years, manufacturers of residential foam insulating products are required to publish a two-year aged R-value.
The rate and degree of R-value drift in foam insulating board depends on many factors such as foam cell size, closed cell foam content, foam board material thickness, and foam board density.
The main factors, though, are the permeance of the foam board facing and how well it is bonded to the foam itself. Metal foam insulating board facings bonded to the wet foam at the time of manufacture (generally aluminum foil) appear to yield the highest R-values.
Through extensive testing at independent laboratories, Celotex Corp. has established that its foil-faced Thermax™ foam board insulation remains stable at about R-7.2 per inch at 75 degF mean temperature for at least five years of aging.
In its bulletin U108, the Urethane Division of the Society of the Plastics Industry lists the stabilized R-value for unfaced foam insulating board or those with gas-permeable facings at R5.6 to R 6.2 per inch of thickness. Consult with the manufacturers for information on specific foam insulating board products.
More Details about Polyurethane, Urethane, and Icynene Foam Insulation Products
Icynene® foam insulation (and similar products) is a spray-in-place, injected through openings, or pour-in expanding-foam insulation product. Other water borne foam spray insulation products, including some latex-foams, are available.
Wind leakage resistance: both open cell foams and closed cell foam insulation products lose less of their R-value when exposed to wind than do some other insulating products such as fiberglass batts.
Spray Foam Systems asserts that the R-value of urethane foam (this is not an Icynene® product) drops from R 19 to R 18 while fiberglass batt insulating drops from R19 to R7 (presuming these are both applied in a 6" thickness).
U.S. Department of Energy studies cite air infiltration in buildings as responsible for 40% of the energy lost in homes (surely varying depending on tightness of construction, house age, etc.)
Icynene® foam and other water-borne foam insulation systems use a water-based solvent, not formaldehyde, or other chemicals associated with prior problem-foam products such as CFCs and HCFCs. Initial foam curing occurs in minutes. When these foams have fully cured (about a month) no VOCs should be detected associated with these foam products.
Fire safety protection: foam insulation products can be hazardous in a building fire and in general must be protected from direct exposure in occupied spaces (such as covering with drywall) in order to assure that potentially dangerous gases are not released into the living area during a fire. See the industry's fire safety guidelines for details, an example of which is provided in this fire safety bulletin from the polyurethanes industry.
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Steve Bliss's Building Advisor at buildingadvisor.com helps homeowners & contractors plan & complete successful building & remodeling projects: buying land, site work, building design, cost estimating, materials & components, & project management through complete construction. Email: email@example.com
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com
Icynene Corporation maintains a website with information about Icynene® foam insulation products, applications, etc. and is located in Mississauga, Ontario, Canada
Tel: 905.363.4040 Toll Free: 800.758.7325
Asbestos Information Links: Asbestos Detection, Testing, Recognition, Hazards, Field Photos, and Information Sources, including
health-related links such as legal services and information about mesothelioma and other cancers.
Asbestos Identification and Testing References
Asbestos Identification, Walter C.McCrone, McCrone Research Institute, Chicago, IL.1987 ISBN 0-904962-11-3. Dr. McCrone literally "wrote the book" on asbestos identification procedures which formed
the basis for current work by asbestos identification laboratories.
Stanton, .F., et al., National Bureau of Standards Special Publication 506: 143-151
Pott, F., Staub-Reinhalf Luft 38, 486-490 (1978) cited by McCrone
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