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Polyurethane Foam FAQs

Please email your questions and we will post them here.

Question: How does Polyurethane 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 polyurethane foams? 
Answer: These two types of polyurethane foams have different R-values, permeability, strength, and costs. Click here for more information

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

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 polyurethane foam?
Answer:  Typically, spray-applied polyurethane 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 "Polyurethane Foam Caulking" have a higher set temperature and/or density to preclude the use of other off-the-shelf types of polyurethane foams.  I think this would be good for quality control.

Answer:  There are four types of "polyurethane" 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. Polyurethane 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.  Polyurethane caulk stays resilient and adheres to most substrates.  It is frequently also used s an adhesive.
  2. Single-component polyurethane 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 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 polyurethane 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)

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.
  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.). 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.