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              Specializing in Superinsulation

     FOAM FAQs
     Question: How does Urethane Foam actually work?
     Answer: Urethanes are plastics that have gas-filled bubbles that make them light weight and a
     good insulating material.

     Question: What is the difference between open-cell and closed-cell urethane foams?
     Answer: Open-cell foam is soft - like a cushion or the packaging material molded inside a plastic
     bag to fit a fragile object being shipped. The cell walls, or surfaces of the bubbles, are broken
     and air fills all of the spaces in the material. This makes the foam soft or weak, as if it were
     made of broken balloons or soft toy rubber balls. The insulation value of this foam is related to
     the insulation value of the calm air inside the matrix of broken cells. The densities of open-cell
     foams are around 1/2 to 3/4 of a pound per cubic foot.

           Closed-cell foam has varying degrees of hardness, depending its density. A normal, closed-
     cell insulation or flotation urethane is between 2 and 3 pounds per cubic foot. It is strong enough
     to walk on without major distortion. Most of the cells or bubbles in the foam are not broken; they
     resemble inflated balloons or soccer balls, piled together in a compact configuration. This makes
     it strong or rigid because the bubbles are strong enough to take a lot of pressure, like the inflated
     tires that hold up an automobile. The cells are full of a special gas, selected to make the
     insulation value of the foam as high as possible.
           The advantages of the closed-cell foam compared to open-cell foam include its strength,
     higher R-value, and greater resistance to the leakage of air or water vapor. The disadvantage of
     the closed-cell foam is that it is more dense, requiring more material, and therefore, more
     expense. Even though it has a better R-value, the cost per R is still higher than open-cell foam.
     The choice of foam should be based on the requirements for the other characteristics - strength,
     vapor control, available space, etc.
           Both types of foam are commonly used in most building applications. Some are
     inappropriate in specific applications. For example, you typically would not use open-cell foam
     below grade 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. Basically, the choice depends on the
     conditions of each installation. We routinely select from a wide variety of foam systems with
     varying characteristics, depending on the particular requirements of our clients' projects.

     Question: What is the difference between CFC, HCFC and HFC blowing agents in urethane
     Answer: These "Flouro-carbons" have different amounts of chlorine or are designed to prevent
     chlorine release into the atmosphere.

A Division of Building Envelope Solutions, Inc.                Post Office Box 87, North Thetford, Vermont 05054
Phone (802) 333-4333 • Fax (802) 333-4364              Web: • Email:

Question: Do urethanes "outgas" and are they toxic?
Answer: Urethanes are non-toxic and only require protection for our operators during
installations, but the finished product is completely safe and has no formaldehydes.

Demelic had an independent testing laboratory test their HEATLOK product for off-gassing.
They tested the product using the Underwriters Laboratory of Canada 705.1-98 test method. It is
a pass/fail test, where the estimated indoor air concentration of volatile organic compounds is
compared to the permissible concentrations. The permissible concentration is defined as 1% of
the threshold limit value. The off-gassing for the HEATLOK product was under the permissible
concentrations so they passed the test.

See the AMA article on toxicity for more information

Question: Are urethanes good for sound insulation?
Answer: Open-cell urethanes are better than closed-cell foams for reducing air-borne sound.
Both are good at sealing holes that can let sound through wall or ceiling penetrations. Structure-
borne sound CANNOT be controlled with low-density infill materials such as foam.

Question: What sort of paint should I use for covering urethane foam?
Answer: Typically, spray-applied urethane foam is covered by interior or exterior wall
coverings or ceiling or roofing details. That said, on occasion it is left exposed and the concern
really is only that of ultra-violet light that will degrade the exposed foam over time. In exterior
applications, a paint will not suffice, rather a protective coating should be used. The Spray
Polyurethane Foam Alliance provides an excellent resource for selecting the appropriate coating
for your application, and we recommend that you visit their website for this information.

Question: I've been thinking that I can specify in our air barrier specification - products section,
that foam used for the "Urethane Foam Caulking" have a higher set temperature and/or density to
preclude the use of other off-the-shelf types of urethane foams. I think this would be good for
quality control.

Answer: There are four types of “urethane” field-processed materials that could be involved in
creating a complete air barrier system - I'll do my best to summarize the materials and their
typical uses.
    1. Urethane caulking: this is a sealant, but is not a foamed product, comes in a tube for use
        with a caulking gun, and would be used for small cracks, including the seams of exterior
        sheathing as an alternate to Tyvek. Urethane caulk stays resilient and adheres to most
        substrates. It is frequently also used s an adhesive.
    2. Single-component urethane foam sealant: this is typically used in small quantities for
        sealing cracks too large for caulking, window and door rough openings, pipe and wiring
        penetrations, etc. This comes in expanding and low-expansion formulas and is very
        controllable which makes it attractive for this type of air- sealing work. This is a
        relatively low-density product that has a low R-value and is permeable. It comes in

A Div. Of H.C.Fennell, Inc.                                  P.O. Box 87 Rt. 5 No. Thetford, VT 05054
Phone (802) 333-4333 Fax (802) 333-4346      Web: Email:

         disposable aerosol cans or in disposable cylinders that screw on to a reusable portable
         gun. It costs between $8 and $12 per pound (not including the cost of the reusable gun).
         (Examples: Pur-Fill, Todol, Zero-Draft).
      3. Two-component urethane foam insulation/sealant in "portable" or "disposable" kit
         systems. This type of foam comes complete with a set of plastic hoses and a gun for the
         professional or the do-it-yourselfer. These kits are used in remote locations or for small
         projects where full-scale equipment is not cost-effective and can be used for air sealing or
         insulation. Density and closed-cell content (less permeable, more R-value) are higher
         than the single-component foam; therefore, it is getting closer to the physical properties
         of a "real" machine-processed polyurethane. Again, the cost of the material is relatively
         high ranging from $5 to $10 per pound. At this level of material use, the OSHA
         requirements for supplied-air equipment kick in. (Examples: Instafoam Froth Paks, Handi
         Foam, Zero-Draft). Note: We have tried a number of single-component "portable" or
         "disposable" kit systems over the past 20 years. None of them has ever been approved
         for use by our crews after in-house testing. They didn‟t process correctly, didn‟t ever set
         up, etc.
      4. Spray-applied polyurethane foam (SPF) and injected polyurethane foam insulation /
         sealant systems are materials processed through high-tech permanent equipment.
         Materials can be processed in a variety of densities at much higher rates than with any
         type of portable equipment discussed above. Raw materials costs range from $1.30 to
         $2.20 per pound and have high R-values, low permeability, and are stronger than lower
         density products. Open-cell urethanes like Icynene can only be processed through full-
         scale equipment. (Examples: Icynene, Heatlok, SUPERGREEN FOAM, Corbond II)

Now to address the temperatures. The bottom line is that it depends on the brand and foam
system. Most manufacturers of machine processed foam systems have hot and cold weather
versions of their products. The retail products (cans and kits) are usually more forgiving as they
are designed to be simple, but they don't have to do much except make a seal. Dimensional
stability, aged R-value, etc. are less important in lower density sealants than for serious
insulation / air and vapor barrier materials.

      1. Caulking (tubes): All of our stock is on the road with the trucks, but the other types
         (latex, silicone, hybrids, etc.) all say above 40 degrees F.
      2. Foam sealants (cans): Pur fill 1G says can must be 60 to 80, but doesn't give a substrate,
         ambient, or curing temperature. There is reportedly a new product on the market called
         Zero Draft. Its product data sheet indicates that it can be installed down to –4 degrees F.
         We have not tested this material yet in the field.
      3. Portable units (kits): Product data related to processing temperatures is scarce, but our
         supplier says he recommends 45 degrees F as the lower limit for this and the Pur fill
         products he distributes. The published service temperature range for the Insta-foam kits
         is -47 to 176 F. The Zero Draft products may be available in a two-component kit form
         as well.

A Div. Of H.C.Fennell, Inc.                                    P.O. Box 87 Rt. 5 No. Thetford, VT 05054
Phone (802) 333-4333 Fax (802) 333-4346        Web: Email:

      4. Machine-Processed Systems: At the "big dig" we used foam that could be sprayed on ice
         and snow (down to say 10 degrees F) and we do steam pipes (up to 250 degrees). Most
         normal foam insulation systems range from 20 to 120 in the product data sheets. Material
         storage, processing, substrate, ambient, curing, and service temperatures and durations
         vary significantly from product to product. SUPERGREEN FOAM has a lower limit for
         processing of 60 degrees F, but installation techniques can stretch the limits a little (pass
         thickness, etc.). Corbond„s winter formulation can be processed down to 20 degrees F.
         Icynene claims a much colder processing ambient or substrate temperature where closed-
         cell foam is not required. Published service temperatures for all of the urethanes we use
         are from -40 to 280 degrees F.


A Div. Of H.C.Fennell, Inc.                                    P.O. Box 87 Rt. 5 No. Thetford, VT 05054
Phone (802) 333-4333 Fax (802) 333-4346        Web: Email:

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