Nuggets mined from today’s episode:
Spray foam is manufactured either in a factory or in situ by combining a two-part chemical mixture with specialized equipment. The A side is isocyanate (methylene diphenyl diisocyanate, an aromatic diisocyanate, most often abbreviated as MDI). The B side contains the catalyst, fire retardant, blowing agent and approximately 75% of the total is polyol resin.
Spray foam creates an exothermic reaction when parts A and B are combined. The heat boils the liquid blowing agent creating the cells.
Open-Cell foam has lower density ½ pound per cubic foot, 3.5-4.5 R value per inch and serves as an air barrier and insulation. Open-Cell foam is never a vapor barrier.
Closed-Cell foam has a density of 1.75″-2.75″ per cubic foot, approximate R factor of 6.5 per inch. Closed-Cell foam is an air barrier at any thickness, insulation, and a vapor retarder at various minimum thicknesses depending on the density.
Spray foam insulation adheres well to many surfaces and substrata. Spray foam will not adhere to oil, water, snow or wax and peels off (delaminates) when in contact with polyethylene. Schedules of materials with which spray foam is compatible are available on line.
Spray foam can be applied when the insulation side is 50°F-100°F. Some special cold weather formulations containing more catalyst can be applied as low as 20°F.
Spray foams needs to be applied in a 1:1 ratio. The temperature of the chemicals prior to processing is important. Closed-Cell foam insulation typically should be applied in a single 1.5″-2″ thick pass. (There are some new formulations that allow greater thickness passes) A dwell time of 10-30 minutes is specified by the manufacturer between passes to allow cooling. Open-Cell foam can typically be installed in an 8″ thick pass. (again, there are exceptions) Heat boils the blowing agent which causes formation of the tiny bubbles. Open-Cell foam uses a different blowing agent (typically water), doesn’t get as hot as Closed-Cell foam, and doesn’t decompose due to excessive heat accumulation. Excess thickness during installation causes excess heat buildup which can cause char/burn out in the cells in the core. The core temperature of the foam should be below 140°F before the next pass is installed. The exothermic heat of reaction of closed-cell spray foam has been known to cause a fire. Filling a large garbage can with spray foam will cause a fire.
Spray foam manufacturing is dependent on equipment. Displacement pumps push Part A and Part B chemicals in an ideal 1:1 ratio through separate hoses to nozzle where chemicals combine and produce the foam. Proper 1:1 ratio is needed for proper (complete) chemical reaction. Installers often use a depth guide to maintain uniform application thickness. As a confounding airspace may exist, core sampling is the most accurate method to determine uniformity of foam thickness if the foam is not bonded well to the substrate. Sample areas are easily repaired after sampling.
Going off the recommend 1:1 ratio results in an unreacted raw chemical that causes problems. When foam is applied in situ, monitoring of chemical temperatures and chemical flow rates is necessary. To prevent problems, Henri recommends weekly equipment calibration.
Unreacted isocyanate crystalizes, is benign because it reacts with water vapor in the air. Spraying more foam over unreacted chemicals can result in dimensional instability and cracking. 80% of installation problems are the result of mixing ratio issues. The next contender is spraying too thick.
Manufacturers provide processing and installation specifications which are the key to determining in-place density. Visible frontiers form between passes. Core samples can be drilled or cut out and sent to a lab. The lab will subject the sample to heat and cold to test for swelling and cracking. The lab will also examine the outer skin surface and the core for abnormalities.
- Spray foam workers must wear proper PPE. Special respirator cartridges and/or supplied air.
- Statistics demonstrate that less than 1% of foam insulation installations have problems.
- Sometimes people read about foam insulation problems online and then manifest? the problem.
- Problems may be localized or isolated.
- Most calls he receives are for valid problems.
- While foam insulation isn’t a food source for mold, mold can grow on the outer surface due to the presence of dust, moisture, and mold spores in the air.
Odors that occur immediately after an installation indicate a “problem application” or inadequate ventilation. Some odors may smell fishy or like urine. The odors can vary due to differing formulation chemistries. The A side has no odor and is an irritant to the installer not to occupants. B side may contain 5 different chemicals some of which are trade secrets. When confronted with an odor complaint, Henri recommends seeking ingredient disclosure and cooperation of the manufacturer. Only testing labs can diagnose foam insulation off-gassing problems. The testing lab will heat a sample taken from the worksite and analyze chemical outgassing in the headspace. Air samples can also be taken in the building.
Installation should appear uniform in color, smooth and regular; not lumpy. Good material can be poorly applied by a bad technician. Good technicians should be able to achieve a uniform foam thickness of ½” plus or minus. Bad looking foam can still perform. Varying depth of 3″ and 4″ will average out to an overall performance equivalent of 3.5″. Cells aren’t visible on the surface, cells within the foam should be approximately 1/16″in size. Cells should be uniformly sized. Occasional “blow holes” are OK, usually caused by concentrated blowing agent. Some foam manufacturers add dyes as a trademark.
Foam should only be applied in unoccupied buildings. Foam manufacturers will specify the time period during which occupants remain out of the building (Usually 24-72 hours). Most installers only depressurize their work areas. Installers must be aware that during foam installation as the work area gets tighter they need to adjust the balance the flow of fresh air in and out. Do not exhaust vapors outside where people may be exposed. Ventilation is required during and after installation. Combustion appliances may backdraft if the ventilation is not balanced.
Remediation and Repair Options:
Odor issues- neutralize the chemicals which haven’t been fully reacted. Some cleaning and neutralizers may make matters worse. Vinegar has been used to neutralize unreacted amines. Isolation, encapsulation, installation of barrier (foil scrim or encapsulant), with depressurization and exhaust behind the membrane, like a radon system, have successfully been used. Applying Closed-Cell foam over foam with an odor issue reduces the rate of odor release and can be coupled with low level exhaust ventilation. Isocyanate doesn’t cause odor problems.
Repair- when foam ratio isn’t too bad and odor is not a problem, stabilize cracking by relieving internal stresses and sealing cracks by skim coating with foam insulation.
Consumer Tips:
- Don’t be a guinea pig, choose a product with an established track record.
- Use an experienced installer with an established track record who is familiar with potential problems which can occur.
- Review info on manufacturers website.
- Know the risks, require a written safety plan.
- You won’t be able to police the work, for safety reasons you shouldn’t be there and unless you are familiar with the work and the process you won’t notice anything unusual.
Final comments:
Foam insulation is the best (insulation) product in the world, but it needs to be installed properly. It solves vapor problems and works where other products won’t. Installers, just have to do it right.
Z-Man signing off
Trivia Question:
Polyurethane spray foam insulation was developed and used by the military in the 1940s. Name the type of military equipment to which it was first applied?
Trivia Answer:
Aircraft – Used in the wings which were foam-core stressed-skin panels. Lighter, and therefore more maneuverable than our ribbed wing design.
